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Electric street transport is equated with clean, breathable city air, something that opinion polls have constantly shown almost everyone wants.
The gentle whine of the electric motor is seen as a 'forward looking' friendly sound - unlike the 'roar' of the internal combustion engine.

Although this page primarily talks about buses, the environsensible etc., benefits of electric traction discussed here apply to all the different types of transport looked at on this website.

Navigating through this website is easier with the navigator frame which should be to the left of this window. If it is not there then click here to turn it on! Alternatively there is a system map at the foot of this page. More information about this website & why it was created can be found by visiting this website's "front" pages (link opens in a new window).

Most images are "clickable" - run the mouse over them and if a "hand" appears then click & a larger version will open in a new window!

Page Index.

Electric Bus Advantages!

In addition to the absence of tail-pipe exhaust fumes, other advantages of electric buses include:-

Improved hill climbing capabilities (especially trolleybuses).
Lowest possible noise levels.
No idling motor energy losses. (ie: when calling at bus stops or stopped at traffic signals)
Better overall performance and less vibration (none whilst idling!) which results in a faster, more comfortable, smoother and hence more attractive journey experience for passengers.
For bus operators faster journeys reduces the fleet size & the number of trolleybus drivers required to operate the route - producing a notable bottom line improvement - whilst less vibration results a longer vehicle life.
Lower and more predictable operating costs - compared to the 'volatile' price and availability of imported fossil and other liquid fuels - even moreso when exchange rate issues are taken into account.
Fewer moving parts and the 'slide out / slot in' modularity of the electric traction packages which makes for simpler and cheaper maintenance.
Regenerative braking which allows them to use their motors as generators and recycle energy either into the batteries, capacitors or overhead wires instead of wasting it as friction / heat via the brake pads. Typically regeneration brings energy savings of around 25% - 30%, depending in vehicle, duty cycles, the weather...
Experience gained from railway electrification which has shown that the sparks effect does attract more patronage, even if low road speed limits and traffic conditions mean that the actual journey times are only slightly improved.
Lower overall lifetime costs - although the initial investment in vehicles and infrastructure (if needed) will make electric buses appear to be a more expensive option than simply buying a few more motorbuses.
With trolleybuses the presence of the infrastructure both acts as a continuous advertisement for the system and helps instill confidence that the transport will be here today - and tomorrow(!), thereby encouraging businesses to make investments in the served corridors.
With battery electric buses recharging the vehicles during off-peak hours (typically overnight) eliminates any issue of capacity for electrical generation.

Electric Buses Are P o p u l a r With The Passengers!

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The space age designed 'Cristalis' trolleybuses in Lyon, France.
These are the 'rigid' (non-articulated) versions.
An articulated Cristalis on one of the high profile
Trolleybus Rapid Transit routes in Lyon.
Image & license: Ibou69100 / Wikipedia encyclopædia. CC BY-SA 3.0

Proof Of Their Popularity Comes From Experience In The Towns & Cities Which Use Them!

In Arnhem, Holland the transport operators saw ridership increases in the order of 17% on routes converted from diesels on a "like-for-like" basis. Their five year "Trolley 2000" Trolleybus Rapid Transit (TBRT) strategy was conceived knowing that by using trolleybuses passenger levels would rise by up to 21% higher than could have been expected using the best type of diesel buses. In Salzburg, Austria ridership increases have been 16% and the city is part way through a long term trolleybus expansion project which includes several brand new trolleybus routes (one of which will be an express service with the overhead wiring configured for overtaking) and converting several more diesel routes to electric operation. Another aspect of these ambitious plans is to see an almost total elimination of fossil fuel powered buses from Salzburg's streets. This is being done for environmental reasons. Increases in ridership have also been noted in the USA, for instance Seattle and San Francisco where experiences have been even more significant because not only has it been found that electric buses will attract more passengers than the diesels but also that replacing electric buses with diesels (even temporarily) can lead to passengers pro-actively choosing to avoid the buses! (almost certainly similar would have been found here in Britain, if anyone had bothered to conduct a passenger survey)

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Salzburg, Austria takes air pollution issues seriously and as part of a plan for total elimination of fossil fuel powered buses from its streets has converted more diesel bus routes to its already extensive trolleybus system.

This image shows one of the new (in 2012) Metro styled trolleybuses with a sloping tram-like front at the bus station which is next to the main railway station. Plus the trolleypoles from another trolleybus!
Image & license: Ralf Roletschek / Wikipedia encyclopædia GNU FDL 1.2
In Arnhem, Holland they found that a service which is busy enough to justify a bus every 10 minutes - six buses an hour - is cheaper to operate with trolleybuses than motorbuses.

The San Francisco passenger survey found that while the streetcars are the overwhelming 1st choice - even for routes where they are not a viable proposition - the electric buses are considerably more popular than the motorbuses, which are actively disliked, being rated as noisy and smelly. Indeed when roadworks caused temporary motorbus substitution of some electric bus services (with service frequencies and journey times remaining unchanged) there was an 11.33% downturn in passenger patronage that can only be explained by passengers making a pro-active choice to avoid the motorbuses.

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San Francisco, USA - passengers like their electric street transports (modern streetcars, historic streetcars and trolleycoaches) - and given a choice pro-actively avoid motorbuses, which they see as being noisy and smelly.

Clean And Other Energy Sources

In an ideal world the electricity would be sourced from renewable sources (wave / geothermal / hydro, etc) as then the electric street transports would be truly 100% non-polluting and help humankind to follow policies for sustainable development. Wind power is also already used, in a few places, although many people would suggest that experience has shown it to be too fickle to be relied upon and is perhaps more suited to domestic micro-generation. Solar power also has many benefits, especially for lighter duty applications such as office lighting, with excess energy harvested during the hours of daylight being fed into the national grid. Wave power is perhaps best suited to coastal communities. The renewable clean energy source which with present-day technologies would probably be the most reliable is geothermal, as it will work at all times, irrespective of whether the weather is windy or calm, daylight or after nightfall, the sea is calm or rough. Geothermal energy does not add to air pollution! Once the facilities have been constructed the cost of the energy should remain the same over many decades.

Even When The Electricity Is Sourced From Fossil Fuel
There Is Still A Reduction In Global Air Pollution!

Critics often allege that by sourcing electricity from fossil fuels all that is really happening is that the pollution is being shifted up the energy chain to the power station. However, following extensive research in the University of California it has been found that even with low grade coal that produces a lot of carbon dioxide (as is used in Germany) electric traction offers an almost complete elimination of carbon monoxide and hydrocarbons, resulting in a significant global air quality benefit. Of course if the fuel used is high grade coal or natural gas (or another so called 'cleaner' fossil fuel) the benefits are even more admirable. Experience in Sweden has shown that when a type of coal-burning power station known as 'pressurised fluidised-bed' is used then the emission of sulphur oxides and nitrogen oxides are also considerably reduced; furthermore, when these facilities are linked in with combined heat and power facilities (ie: provides both electricity and hot water which can be made available to industrial and domestic consumers alike) then they are about 40% more efficient than their traditional large coal burning equivalents (ie: 75% efficient opposed to 35% efficient) and are so clean that they can be located within cities.

As a contrast at best diesel engines are only 40% efficient and if you include idling, part loads etc., then this reduces to below 30%. Engines powered by other fossil fuels achieve even lower figures. Plus all the pollution is released in the street environment...

In some areas natural gas is used to create electricity. Typically this is less polluting than coal.

Uh-Oh Energy Sources
Best Avoided For Long-Term Human & Planetary Health

Sometimes gas is sourced by a method known as fracking. Typically this destabilises the ground, damages the local water tables and has other undesirable local geophysical effects.

Many countries source electricity using nuclear power, although what happened because of the melt-down of several of the Fukushima reactors in Japan has alarmed so many previously unaware and disinterested people that there are now many people who are opposed to more nuclear power stations. Nuclear power generation also leaves much radioactive waste material which could be described as an obnoxious, poisonous gift that this generation is bequeathing upon the next generation. It is understood that whilst it is possible to process and reprocess nuclear waste until it is actually safe, and gain much extra electrical energy whilst doing so, there is a rarely-spoken reason why the people in power do not permit this to be done. This could be military and be connected with nuclear weaponry. Some people advocate Thorium as a safer alternative to uranium, some even suggest that as with what is known as cold-fusion there are powerful people in established very wealthy fossil-fuel industries who stand to lose too much to allow any true alternative (that is not already being used) to be commercialised; it is beyond the scope of this page to say any more on this topic.

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Modern rigid (ie: not-articulated) trolleybus in São Paulo, Brazil.
Image & license: Rafael-CDHT / Wikipedia encyclopædi. Public Domain.
Trolleybuses come in many different vehicle lengths - including triple axle 15 metre rigid variants, as seen here on demonstration in Salzburg, Austria. Image courtesy of Bruce Lake.

Electric Buses Are Environmentally Sound!

The environmental case for electric traction is that even with so-called 'cleaner' (but still finite) fossil fuels (eg: LPG, CNG, etc.,) the only proven viable vehicle propulsion system that will not pollute the air that we breathe in our towns and cities comes from electricity. Whilst renewable liquid fuels are available (gasohol, bio-diesel, etc.,) they still pollute their local environments so are more suited to quieter rural routes where air quality issues are less severe and economics suggests that electrification would simply not be a viable proposition.

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What a pleasant, fume free contrast to London:
Modern trolleybus in Geneva, Switzerland sharing
the pedestrian zone with the trams.
Trolleybuses also travel along part of the
pedestrian zone in Neuchâtel, Switzerland.

projector icon A video showing a seriously (air) polluted bus + taxi pedestrian zone in London plus this clean air equivalent scene from Geneva has been placed on the 'youtube' file-sharing website and can be watched (in a new window) by clicking the link below.

So, Knowing The Benefits, Why Aren't More Cities Investing In Electric Traction?

Perhaps the primary reason why more cities (outside of Britain) are not investing in electric traction is that the continuing limitations of battery technology means that the only way to obtain sufficient electrical energy for a full days' work is by making that energy available wherever the vehicle happens to be, and the only proven viable way to achieve this (and maintain safety within the street environment!) is through the installation of an overhead wire power supply system. Its unfortunate but every community has its negatively orientated NIMBY (not in my back yard) type of people and it seems that a few of them dislike these overhead wires. Oddly enough though, these people are hardly ever heard complaining about the clean, breathable city air that electric traction brings!

Trolleybus System Installed - To Protect Urban Environment

As part of a policy for cleaner urban air, and having investigated all the alternatives and the financial benefits from reduced healthcare costs, in March 2005 the Italian capital city of Rome opened its fist trolleybus route since 1972.

These vehicles also feature powerful batteries giving them an expected 10km off-wire range. The reason for this is that within Rome city centre there is a 3km unwired section and in an effort to maintain urban air quality the use of diesel (or other fossil fuel) power systems was felt to be undesirable. The extra long range of the batteries is also to ensure that they have the endurance to cope with traffic delays in stop start (rush hour) travel conditions and to guarantee power to the brake compressor & air conditioning. Battery mode operation will usually include 5-15 minutes laying over between journeys at the central bus terminus in Rome city centre - during which time the buses remain in batter electric mode.

Recharging takes place whilst running under the wires.

In January 2008 Rome announced the creation of a 60 vehicle trolleybus system serving another part of the city. However, with experience showing that battery operation represents an Achilees Heel so the next batch of 45 trolleybuses will include super-capacitors (for onboard energy regeneration) and Euro 5 reduced pollution auxiliary diesel engines for the unwired areas. Unfortunately whilst by summer 2013 work had started on this project and the new trolleybuses had all been built and placed into store, there have been delays in installing the overhead wiring infrastructure. Media reports cite two reaons for the delay, these being related to questions of irregularity related to the project's finances and an archaelogical survey.

The Tangenti Filobus (trolleybus bribes) financial scandal has also involved the construction of metro line C and has been so wide-ranging that it became front page headline news as well as the subject of television programmes and several court cases. It is likely that one or more people will end up being jailed.

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Rome trolleybus operating in battery mode just after leaving its stand at the "Termini" bus station in the city centre. Rome trolleybus in overhead wire mode travels along a segregated Bus Rapid Transit lane in Via Nomentana.

Why The 'Double-Standards?'
Surely Buses Should Be As Clean As Trams?!

Trams (streetcars) are almost always electrically powered - indeed this feature is often touted as one of their major benefits - and there really is no reason why buses should not be equally city (and town!) friendly. It really is most strange that so many transport 'experts' (& environmental advocates / lobby groups etc) have such double-standards with respect to air quality (or lack of) and bus / tram propulsion systems.

As yet none of the proposed tram systems for Britain have been advertised as using diesel powered trams, yet (almost) all the proposed British bus-based rapid transit schemes feature diesel (or other fossil fuel) powered buses.

See caption for picture information. Zürich, Switzerland, where as part of environmental policies designed to protect the health of city-dwellers by minimizing urban air pollution motor buses are generally restricted to outer suburban and rural services.

Trams (streetcars) are almost always electrically powered - indeed this feature is often touted as one of their major benefits - and there really is no reason why buses should not be equally city (and town!) friendly.

It really is most strange that so many transport 'experts' (operators, environmental advocates, lobby groups etc.,) have such double-standards with respect to air quality (or lack of) and bus / tram propulsion systems

Bus Derived Air Pollution Is The Easiest To Solve

Whilst it is true that motor buses are not the only vehicles which create tail-pipe pollution (cars, lorries, motorcycles and taxis do too) bus derived air pollution is the easiest to solve. This is because buses generally follow fixed routes along comparatively few of the roads in a cities' overall street network. Effectively this means that significant air quality gains can be achieved by equipping just a few roads for trolleybuses.

Whilst modern trams (streetcars) usually collect their power from a single overhead wire via a pantograph fitted to the vehicles' roof (with electrical return being via the running rails) electric buses will use a pair of overhead wires (one each for power & return) and twin 'trolley' poles fitted to their roofs. This explains why they are called "trolleybuses".

In North America they also use other terms, such as trolleycoaches; etb's / electric trolley buses (to distinguish them from diesel-powered 'trolley' buses that look like an old fashioned "trolley-car" as is often used in the leisure industry) & trackless trolleys - "trolley" is another American term for "tram" or "streetcar" so a trackless trolley is a "trolley car" that collects power from overhead wires using "trolley poles" but travels without rails.

Although there are upfront investment costs associated with new trolleybus networks - and because they tend to be built in small batches the vehicles themselves are more expensive to purchase - experience has shown that once operational trolleybuses can be cost competitive with diesels if you take a "lifetime" view of an installation (20 years or so) and factor in their expected longer life, lower maintenance costs, increased availability, increased attractiveness to passengers (higher revenues), better energy efficiency, etc. In Arnhem (Holland) the management of the trolleybus system have quoted about six vehicles per hour (10 minute headways) as about the break even point when it becomes more economic to operate a service with trolleybuses than diesels.

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Modern rigid (ie: not-articulated) trolleybus in Wellington, New Zealand
Image & license: User:Vardion / Wikipedia encyclopædia CC BY-SA 3.0
Some very busy trolleybus routes in Lüzern, Switzerland are served by 'rigid' trolleybuses which haul unpowered low-floor easy-access trailers. This is because increasing demand meant that overcrowding was becoming an issue so larger (articulated) trolleybuses were needed, however as the existing vehicles were not life-expired it was decided that using trailers would provide a cost effective solution which both increased passenger capacity and introduced low floor accessibility for the first time.
See caption for picture information. High capacity three-section double-articulated LighTram trolleybuses (as seen here) were designed to increase passenger capacity on busy trolleybus routes - as an alternative to converting them to (steel wheel) trams.

These image come from the Swiss cities of Geneva left,
and Zürich below - the latter image comes from Wikipedia.
Image & license: Micha L. Rieser / Wikipedia encyclopædia CC BY-SA 3.0

Similar vehicles are also used in the Swiss cities of Lucerne (Lüzern) & St Gallen.

See caption for picture information.

As of Spring 2007 Geneva decided that to both cater for the increasing numbers of passengers travelling and reduce urban air pollution it will convert its busiest trolleybus routes to tram - and then use the displaced trolleybuses and LighTrams to both lengthen existing trolleybus routes and electrify more motorbus services. In Geneva they have found that the sight of the overhead wires is seen as a positive advantage, because "people see the wires and know that quality public transport comes here" (ah, so different to this country).

Trolleybuses Are Flexible Enough To Avoid Road Obstructions!

Trolleybuses can travel with the overhead wires either directly above or to one side of the vehicle. Usually their ability to 'wander' is by as much as four metres, which equates to three traffic lanes.

Apart from helping them to fit in with existing traffic flows this ability to switch lanes also gives them an ability to around obstructions, such a broken down cars.

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click me for video Trolleybuses have the flexibility to go around obstructions, such as broken-down cars! Esslingen, near Stuttgart, Germany.

The above image is a video-still - click the image or the projector icon to download a 17 second video clip named 'Esslingen-go-around320.mpg' which shows the action being described as well as a duo-bus running with its trolleypoles down.
Flexibility also means easily coping with having to use the other side of the road when road reconstruction results in single alternate lane working under the control of temporary traffic signals. Solingen, Germany.
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Gdynia, Poland. Because trolleybuses can use several traffic lanes so at bus stops with dedicated pull-ins the overhead wires just need to be slewed towards the pull-in to be suitable whether the trolleybuses are calling here - or not.
Image & license: M.M.Minderhoud / Wikipedia encyclopædia CC BY-SA 3.0
A simple passing loop in the overhead wires allows a moving trolleybus to pass a stationary trolleybus. Lausanne, Switzerland.

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Extending Beyond The Wires...

Many modern trolleybuses are also equipped with either a low power fossil fuel engine or batteries so that if they need to travel away from their wires they can do so, albeit perhaps at reduced speed. Another use for these secondary power systems is in the depôt, giving them the ability to gain access to every part of the facility without having to provide sufficient wiring.

In most instances these APU's will only be for emergency (& depôt) use allowing the vehicle to travel a short distance around an obstruction (eg: a road traffic accident) at reduced speed. However in some cities they use more powerful alternative power systems as this can give the possibility of scheduled operation of longer distance off-wire travel too.

In Landskrona, Sweden - which opened a small brand new trolleybus system in 2003 - the bus garage is unwired and around 1km away from the nearest wiring. The first vehicles in the fleet use batteries to power the trolleybuses between the bus garage and the service wiring, but when increasing passenger numbers (from 200,000 to 500,000 a year) resulted in fleet expansion it was decided that the new trolleybus should be equipped with a low power diesel apu instead. With passenger numbers still increasing 2013 saw another trolleybus being added to the fleet.

Rome's first present-era trolleybuses feature batteries powerful enough to allow as much as 3km of unwired operation through the heart of the city centre, albeit with the air-conditioning switched off. The option which Rome did not want to follow is to use what is known as a duo-bus (see below) - this was for reasons of air quality.

In Beijing, China, all the routes crossing the main east-west boulevard or operating through the central shopping streets do so using powerful batteries which permit quite smart acceleration and several kilometres range at 30-40 km/h. After crossing the visually sensitive areas the trolleybuses are driven into a marked box on the highway where the driver depresses a button to raise the trolley booms hydraulically into inverted V-shaped re-wiring troughs on the overhead. As with Rome's trolleybuses the batteries are recharged during the remainder of the journey.

Rear view, showing mid-air trolleyarms just under the wiring guides. See caption for picture information.
Rome trolleybus raising its trolleyarms to switch from battery to overhead-wire power. In the view on the right the pick-up has yet to properly locate itself around the overhead wires.


Duo-buses are 200% power vehicles which can operate freely - at full power - in either electric or fossil fuel modes. When in electric mode they operate as trolleybuses, collecting power from overhead wires via twin trolleypoles. In diesel mode they use a normal mechanical transmission system, just like normal diesel buses. These are NOT hybrid buses, there is no energy storage - they are strictly diesel or electric at different times.

Used in a few cities globally, duo-buses are usually fitted with motorised trolley poles, so changing between modes is simply a case of the driver stopping and pressing some buttons - (s)he does not even have to leave the cab! When raising the trolley poles correct placement is ensured by fitting inverted 'V' shaped wiring guides to the overhead wires, naturally for them to be effective the vehicle must stop in the correct location, so it is very important to prevent illegal parking at the up-points. Lowering the poles can take place anywhere, even when the vehicle is moving. In either case modal changeover takes less than a minute so when it is located at bus stops the only delay to the service comes from the time taken for the passengers to pay the driver as they board.

Duo-buses are more suited on routes where buses need to operate significant distances beyond the range of the overhead wires but the route is infrequent and therefore electrification is not commercially viable. Apart from the effects of the waste gases the primary disadvantage of the duo-bus is that the weight of the two drive systems increases their unladen weight and if this brings them close to the legal weight limit for buses it potentially could reduce the passenger carrying capacity.

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Esslingen, Germany duo-bus using its auxiliary diesel engine to go around a maintenance crew working on the overhead wires. Massachusetts Bay Transportation Authority (MBTA) Silver Line Dual-mode bus departing South Station to serve SL2 Waterfront Line in Boston.
Image & license: Xb-70 / Wikipedia encyclopædia. Public Domain.

In the late 1980's and early 1990's the German city of Essen had a fleet of duo-buses which mostly ran as diesel buses when on surface sections of route and as trolleybuses when travelling through part of the city's underground tram / light rail system.

More information on the former underground operation of duobuses in Essen can be found on these pages...
Buses02.htm#Kerb (condensed version) and
Kerb Guidance - The 'O-Bahn'
(full version, with many pictures, NB: large page, opens in a new window).

See caption for picture information.
This image shows one of the duo-buses raising its trolleyarms whilst stopped on a tunnel entry ramp.
NB: The clickable large image has been sourced from S-VHS-C videotape and is a little fuzzy.
projector icon
A film showing an Essen duobus switching between electric and diesel modes has been placed on the 'youtube' film sharing site and can be watched (in a new window) by clicking either the projector icon or this link. It was filmed in 1990 at the Viehofer Platz bus & tram stop which in 1991 was replaced by the tunnel extension, which (as other youtube films show) was also used by the trolleybuses!

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And In Britain?

In 1986 a planned trolleybus scheme in Bradford was scuppered because the British deregulated bus operating regime - which actively encourages cut throat 'free-for-all' competition between private bus companies often plying the same streets - encouraged a 'spoiler' company to split the fare base by introducing a rival service (along the same route) which would compete by providing part-time services using cheapo secondhand minibuses. A negative side affect of this was that the perhaps little-known proposals for trolleybuses in the nearby towns of Doncaster and Rotherham were also scrapped, although the planned tramway in Sheffield is now a reality.

With the Doncaster and Rotherham schemes in mind a prototype double deck trolleybus was built and a short stretch of overhead wiring erected between a bus garage and the nearby Doncaster racecourse, with these trials proving that it would be possible to build a trolleybus at very low cost with virtually no changes to the chassis and coachwork of what was otherwise a 79 seater diesel double deck bus.

Since then it has become pretty obvious that the free-for-all system of bus operations actively inhibits serious fixed-infrastructure transport investments - indeed it also lead to the near bankruptcy of the Sheffield tramway when rival bus companies set out to compete with the trams by offering low quality secondhand buses and dirt cheap fares.

The only city on the British mainland where cut-throat 'free-for-all' deregulation does not apply is London - here the competition is for the right to operate pre-defined bus routes under contract to the London-wide regional government body for transport, this being known as "Transport for London" (TfL).

So What About London?

London Buses Ltd in its publication "Cleaner Air for London - London Buses leads the Way" estimated that the cost of (human) health care which results from diesel bus air pollution equates to an equivalent of €0.20 (ie: 20 Euro cents) per km. Meanwhile, a different report prepared at the Roma Tre university in Rome suggested the cost as being €1.20 per km. As most readers will instantly note, the Italian figure is significantly larger! Using this figure helps justify for the investment in the new "filobus" (the Italian word for trolleybus) network detailed above because it suggests that installing the electric street transports would result in significant financial benefits in reduced health care costs.

At a presentation given by the TfL Managing Director for Surface Transport he made it quite clear (in a response to a question I asked him) that his primary duty is to run a cost effective transport system and that it would not be commercially viable to care about environmental issues, which in his view are for the government to decide. (He included issues which affect human health in this comment). Then he added that obviously if the government introduced new legally binding standards and / or someone else came up with the dosh (cash) then the situation could change.

It is a most terrible (even criminal?) indictment of our present-day system of government that under British financial criteria the Italian proposals would be seen as "uneconomic". Do we in Britain not value human health? (rhetorical question, of course we the people do, even if our leaders and decision makers just pay lip service to the issue) or is it because of the insane way in which the British government allocates funds to its various departments, with health care costs coming from a different 'pot' which is (not only) totally independent of the transport 'pot' but actually (at a governmental level) competes vigorously for funds against the transport 'pot'?

Poor health caused by air pollution is a big problem in London and with as many as 7000 diesel buses on London's streets it stands to reason that they must be part of the problem - with zero-emission (at point of use) electrically powered trolleybuses being part of the solution. In 1999 more Londoners died of air pollution related illnesses than in road traffic accidents. According to a report published by the Chartered Society of Physiotherapy - CSP - the PM10 air particles which are emitted mainly by diesel engines pose such a serious threat to public health that the World Health Organisation (WHO) believes there is NO SAFE exposure limit. The CSP's analysis revealed very high levels of this dangerous pollutant - not just in London but throughout the UK. The full story used to be found at the link below, however in the intervening time since this page was first written both it and the london.gov.uk links lead to pages which seem to have been deleted.

Data sources: Road deaths - http://www.tfl.gov.uk/assets/downloads/casualties_in_greater_london_during_2005.pdf
Air pollution - http://www.london.gov.uk/view_press_release_a.jsp?releaseid=21899
CSP's analysis - http://www.csp.org.uk/search/result.cfm?item_ID=

The Electric Tbus Group has conducted a detailed study which suggests that for London the conversion of the busiest bus routes (eg: those with a frequency of every 5 minutes or more) would offer significant financial and environmental benefits. Thanks to the network effect where multiple routes operate along the same roads the situation would soon arise whereby many subsequent conversions would entail less additional wiring - both increasing the cost effectiveness of existing wiring and reducing the cost of the electrification of additional routes.

Plus of course Londoners would benefit from the significantly cleaner air in the streets where they live, work and play.

See caption for picture information. Modern electric trolleybus for the proposed ELT (East London Transit) bus scheme. Image courtesy of the Electric Tbus Group - www.tbus.org.uk
Modern British trolleybus built in the 1980's to promote new trolleybus schemes in the South Yorkshire towns of Doncaster and Rotherham. Because of bus deregulation these failed to happen and this vehicle now lives at the Sandtoft trolleybus museum. Artist's impression of a trolleybus for the East London Transit scheme (see below).
Image: Courtesy The Electric Tbus Group http://www.tbus.org.uk
based on a backdrop supplied by me.

In the late 1990's a serious proposal was made for using trolleybuses in London, but only as part of a small local area "rapid transit" scheme (named East London Transit) where the sole reason for suggesting trolleybuses was because the projected ridership would have been too low to justify the cost of installing a new tramway. According to the "East London Transit - Summary Report" (published by TfL in July 2001) the use of trolleybuses on this 33 mile (53km) high-profile Bus Rapid Transit system for east London & metropolitan Essex would provide the most financially beneficial option, generating revenues 24% higher than a comparable diesel bus scheme.

Public consultations in the areas to be served by ELT were very positive too - especially towards the trolleybuses with public opinion being 2:1 in favour of the clean electrics AND against yet more polluting dirty diesel buses.

Yet despite this TfL back-pedalled and the ELT uses diseasel (disease diesel) buses.

To avoid duplication and side-tracking further information about ELT and modal choice political machinations are on the A Bus For London. page.

The Need For Trolleybuses In Britain!

According to a Government report issued by the Committee on the Medical Effects of Air Pollutants air pollution hastens the deaths of between 12000 and 24000 British people a year and is associated with 14000 and 24000 hospital admissions and re-admissions - causing sufferers and their families untold amounts of misery and costing our health service & taxpayers £billions.

In February 2010 the House of Commons Environmental Audit Committee was informed that the fatality rate is actually at least 35,000 people a year, and based upon some EU studies possibly even as high as 51,000 people a year.

Yet whilst motoring offences (especially speed related) seem to be attracting ever more diligent attention by the various authorities the issue of air pollution only receives the metaphorical "lip service".

In Britain more people die from air pollution than in motor vehicle accidents. The total deaths from road traffic accidents (including pedestrians knocked down) is approx 2,538 (DfT figures, 2008) - and whilst obviously even one fatality is too many the figures are still considerably fewer than the number of casualties which can be attributed to air pollution.

So, 50 years after the clean air legislation resulted in the ending of coal sourced smogs the air that we breathe in our towns and cities is yet again so heavily polluted that people are suffering ill health (and even dying) from it.

It could be asked why our predecessors bothered, only to be failed by future generations.

Many of the most severe sufferers are our children, who when in the street environment are at the right height to breathe in large quantities of particulates as they are blown about by passing traffic. It is no wonder that the incident rate of childhood asthma is now at a record high in our towns and cities.

So (once again) maybe its time to take urban air pollution seriously???

Introducing trolleybuses into British towns and cities would have helped Britain meet its commitment to cutting carbon dioxide emissions by 20% by 2010. The House of Commons environmental audit committee says that carbon emissions from transport are 'still moving in the wrong direction' but apart from clobbering motorists with yet more taxes the govt. has failed to find effective ways to entice people out of their cars. Amazingly with respect to new tram schemes the government actually took pro-active steps to deter these from coming into reality by making their installation more expensive - see the Enough Stick! How about Some Carrot page for more information.

By attracting car users who would not switch to a motor bus electrification of Britain's urban bus routes could help reverse this upward trend. This would also help reduce overall road traffic levels too.

A nationwide programme of bus electrification here in Britain would help us justify to the other members of our planet-wide family of nations the urgent need for similar policies for improving both the global and their local environments. It would also "add value" to people's daily lives - something which current British government transport & environmental policies totally fail to do.

Government Action Urgently Required!

In an email from a major British operator they stated that (apart from the problems caused by bus deregulation, as detailed three sections above click link to go backwards) a significant impediment to trolleybus introduction and operations in Britain - including London - could be easily removed if the government really so desired...

"Trolley Bus systems require complex approval processes bringing further business risks and potential delays. The environmental benefits of alternative fuel technologies are difficult to quantify in cash terms making this benefit difficult to sell to Government when seeking capital funding for projects."...

"Furthermore, the inclusion in the UK of Trolley Buses within the remit of railway regulatory regimes introduces a significant additional burden in terms of the management of the operation and the infrastructure"...

"The combination of these factors makes the consideration of Trolley Buses low on our current plans for investment."

It could be said that the optimum solution for us here in Britain would be to use the same planning processes as are already used for highway improvement schemes, the introduction of bus lanes, bus stop shelters, new traffic signalling systems, replacement of street lighting etc. After all, the works for installing trolleybuses - erecting the overhead wires, building substations (etc) to power these wires and arranging connections to the national grid - will be considerably less disruptive to other road users than road works and about the same as the replacement of street lighting poles.

If new trolleybus systems were installed in conjunction with local government declaring the route a "high profile quality bus scheme" (such as already exist in a few locations) it should be possible to prevent spoiler companies from introducing rival services using cheapo secondhand motor buses designed solely to split the fare base and push the quality buses off the road.

18 Months Or 18 Years?

The British planning process is so very slow that it is looking likely that by the time it opens the Leeds trolleybus scheme will have taken over 18 years to reach fruition.

By way of contrast, in Salzburg, Austria a conversion of a diesel bus route to trolleybuses took 18 months - including all the planning and installation works. That is quite a time difference!

It is not for nothing that the British planning system is said to encourage paralysis by analysis.

Detailed Studies Of Costings.

Detailed studies of costings for new trolleybus systems in Britain have shown that installing the physical infrastructure (overhead wiring and substations) will work out at around £500,000 per kilometre. Of this about half would be for the wiring and support poles, etc., and about half the substation, feeder, etc. The costs of manufacturing and planting the (steel) support poles usually represents the largest item of the actual wiring costs, although once installed they would be expected to last for many decades (....indeed many of the poles planted in the 40's and 50's in towns around the country are still in use for street lighting and the aborted Bradford trolleybus proposals of 1986 would have re-used some of the still extant poles in that city in this way).

Sheffield Supertram and overhead wires using a wall rosette.
Some street sections of the Sheffield Supertram system feature overhead wiring supported invisibly from rosettes attached to building walls. Similar could be done for trolleybuses too.

To reduce street clutter it is often possible to hang wires from wall rosettes on buildings - although unfortunately only certain types of buildings are suitable for this. Alternatively it should be possible for the same poles to carry both overhead wires and street lighting - but this would still require the installation of new support poles as ordinary street lighting poles will not be strong enough to support overhead wiring (and the extra work involved in this latter option could see costs rise).

It is very possible that an enterprising electricity supply company would be interested in a mutually beneficial financial arrangement with respect to physical infrastructure and long term electricity supplies.

Something else which could affect the overall cost of the overhead wiring would be whether the trolleybuses are equipped with auxiliary power units (APUs - either battery packs or diesel generator sets) which allow the vehicles to operate away from the overhead wires. APU's will increase vehicle costs but then there probably wont be a need to install wires for access to the depôt - which could result in a substantial financial saving as to wire a depôt internally can require a great deal of 'special work' - points / switches / frogs, crossings, etc. - which are always very expensive compared with plain wiring.

The nature of the wiring and its source can also cause costs to vary. 'Elastic' overhead wiring from, for example Swiss sources could result in costs working out more than the £500,000 per km quoted above, which assumed British sources.

Yorkshire, A Glimmer Of Hope?

In Summer 2007 the city of Leeds announced proposals for an electric BRT (Bus Rapid Transit) system using trolleybuses. However there is a story here which in many ways demonstrates everything that is wrong with British Government transport policies. Originally Leeds wanted a tram system, however despite much encouragement from the (national) government suggesting that they would look favourably to a request for finance, and after spending £millions of taxpayer's money drawing up proposals, the national govt. happily 'pulled the plug' financially - leaving the local politicians with nothing. So trolleybuses are being looked at in an attempt to salvage something from the otherwise wasted monies spent on the tramway proposals. The idea seems to be to maintain the same clean air benefits as the trams would have provided and follow virtually the same routes too - just that the transports would be rubber tyred and not steel wheeled. However even by November 2011 the national politicians were still stalling on this proposal, with the trolleybus scheme now having to compete against other British transport schemes for a slice of the small 'pot' of available government money. What is planned in Leeds will be a TBRT (Trolleybus Rapid Transport) scheme which includes many bus priority measures that whilst laudable also act to increase the cost of the whole scheme - and restricts the bus electrification to a single transport corridor - when to achieve maximum air quality benefit what is really needed is wholesale replacement of diesel buses with trolleybuses.

2013 Air Pollution Update: Government Taken To Court!

The links below were added to this page in July 2013 and the data in the articles they lead to suggests that the issue of urban air pollution situation is still very serious and includes what amounts to the government seeming to just not care about air pollution and its effects on human health.

A House of Commons Environmental Audit Committee Report which includes the two quotes below and that in 2008 4,000 deaths in London were linked with air pollution, whilst business plans produced by the Department for Transport and Defra did not even mention air quality:

"The Government is putting thousands of lives at risk by trying to water down EU air quality rules instead of prioritising action to cut pollution on UK roads"
"It is a national scandal that thousands of people are still dying from air pollution in the UK in 2011 and the government is taking no responsibility for this.
It is often the poorest people in our cities who live near the busiest roads and breath in diesel fumes, dangerous chemicals and bits of tyre every day.
If you have heart disease, asthma or other respiratory illnesses then living near a congested road like this can literally take years off your life.

This March 2013 newspaper article explains the situation in much detail and includes these two quotes (in fact there is more information than can be reported here:) http://www.guardian.co.uk/environment/2013/may/01/government-pollution-supreme-court

"The latest figures suggest 29,000 people die prematurely from it every year in Britain, twice as many as from road traffic, obesity and alcohol combined, and that air pollution is now second only to smoking as a cause of death".
"In 2011, the House of Commons Environmental Audit Committee calculated that living in an air pollution hot spot could shave nine years off the lives of the most vulnerable people. It concluded that it cost Britain £6-19bn a year, or up to 17% of the total NHS budget, and that 15-20% more people died prematurely from it in cities with high levels of pollution than those in relatively cleaner ones.

In April 2013 the Supreme Court in London ruled that the UK Government has breached its legal duty to reduce air pollution in British cities, and called for the European Commission to take immediate action to enforce EU law. These links explain more (as with all external links they open in new windows)

This July 2013 link to an article about a World Heath Organisation report which reviewed evidence on health aspects of air pollution will also be of interest:

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Other Types of Electric Buses.

This section looks at some other types of electric buses.

Batteries are already well known, and in recent years capacitors have become robust enough to start being used either alongside or instead of batteries.

Then there are some emerging ideas which may become solutions of tomorrow. These include frequent fast charging of batteries or capacitors and power collection from the road beneath the bus.

Battery Electric Buses.

Many people know what batteries are about - after all, who has never used a torch / portable radio / music player / telephone / communications device (etc)? All of these use batteries and it would seem logical that if these work well then buses should be able to be powered from batteries as well.

Ah, if only life were that simple!

Real-world reality is such that battery technology is simply not the whole answer. This is because (especially for large buses) batteries do not carry enough energy to power the bus for a full day. If this were not so then both diesel and overhead wire trolleybuses would already have been replaced with battery buses.

Whilst simply carrying a few more batteries may seem a logical enough solution the reality is that batteries add weight, which increases energy consumption, and since there are usually legally mandated weight limits for buses / all road vehicles so using heavier buses would reduce the total number of passengers they are allowed to carry. Batteries also take up valuable passenger space inside the bus, potentially also reducing its overall passenger capacity.

Another issue with rechargeable batteries is that over time they degrade, which means that the amount of charge they can carry slowly reduces, and the reality is that (at present) none of the known battery technologies has created a battery with the same longevity as the buses. Some battery technologies are still too new to be sure of exact facts but it is looking likely that all electric buses which use batteries to power the vehicles will need their battery packs replacing at least once during their commercial lives. When the cost of the batteries is also bourne in mind this can be expensive! Often after a few years use batteries can be reconditioned, but this process only adds working life to them, it does not return them to full 'as new' condition.

Money is not the only issue. Making / half-life reconditioning / disposing of spent batteries also has environmental consequences. Of course where there is the will to do things properly the environment is easily respected.

All the known and even some unusual battery technologies have been trialled with buses, including lead-acid, nickel cadmium (NiCd) and nickel metal hydride (NiMH). The present-day favourite is lithium-ion (Li-ion), one reason being because these batteries are considerably lighter. Likely to replace Li-ion technology are batteries made from lithium iron phosphate (LiFePO4) / lithium ferrophosphate (LFP) as these avoid the use of heavy metals and poisonous chemicals. Whilst they have a lower energy density than the more common Li-ion designs they are expected to offer longer lifetimes, better power density (the rate that energy can be drawn from them) and are inherently safer. This latter point is important, it means that they are less likely to ignite if mishandled or experience a fault, this being such a significant safety challenge with other designs of lithium battery that complex electronics are required to try and prevent it from happening. When lithium batteries do ignite the resulting fires can be so hot (over 2,000° C) that they can melt concrete.

Note however that the operational, financial and environmental challenges related to battery buses are still easier to resolve than dealing with the human (ill)health consequences of fossil fuel exhaust fumes.

Commercial Experience That Battery Technology
Is Not Yet Robust Enough For Large Buses.

An example of the issues regarding battery life can be found from Shanghai in China.

Included in the public transports for the 2010 World Expo which was held in Shanghai was a dedicated fleet of 120 battery electric buses. During the Expo these were mostly used as tourist shuttles, for which their 80km (50miles) range was sufficient. However they did not perform very well in the scorching summer heat of that year and in order to keep them available to transport Expo visitors the batteries had to be constantly replaced, cooled and recharged.

By 2013 the batteries had degraded to a point where they could only hold enough charge for 60-65 km (37-40 miles) of travel. As the linked news article below suggests, this restricts the services on which these buses can be used, with frequent recharging between journeys becoming a burdensome necessity.

The bus operator reckons that after 4 - 5 years the batteries will need changing, and with the cost of new battery sets (per bus) being about 1.1 million yuan (US$176,765) so the financial burden represents a significant deterrent for more widespread use of battery buses. See here (link opens in a new window):-

Towing battery trailers behind the bus is an option which has the potential to solve the issue of batteries taking up valuable passenger inside the vehicle.

However trailers introduce many new complexities; in short this concept has not found favour - as otherwise many bus systems would be doing it!

Saskatchewan Transportation Company electric bus
and battery trailer at the Bus Service Center, Saskatoon.
See caption for picture information.
Image & license: SriMesh / Wikipedia encyclopædia. CC BY-SA 3.0

Emerging Technologies.

Scientists are feverishly trying to find new solutions to battery life issues, it is not intended to report on them all but what may yet prove to be a gamechanger for passenger transport is that in June 2013 some German researchers claimed to have created a lithium-ion battery that retains 85% of its ability even after 10,000 charges. In theory this means that if a battery is charged once daily then 10,000 charges will take over 27 years to achieve, however since batteries are more likely to be charged several times a day so it could be that they will reach the 85% after just 10 years. This might still be viable, so that the batteries would only need changing once during the expected lifetime of the bus... as ever we will only know through real-life experience when the right time has been reached. See here (link opens in a new window):-

Then there is graphene, which when mixed with nanoparticles of silicon and metal oxides makes batteries of far greater capacity than those that exist today. For many applications graphene will be used in single-atom layers which are known as two-dimensional crystals and the unanswered question which boffins are investigating is how many other materials, when used in this way, will have similar or even more useful attributes? Such as powerful, long lasting batteries?

This is not the place to discuss why this is being suggested, but sometimes on alternative news discussion forums it has been suggested that magnetics can be used as part of a clean and safe source of energy. In tandem with the sort of changes which are expected to be coming on stream when we start using magnetics will be wide ranging changes to our transport solutions, including the possible replacement of rubber tyres (tires as spelt in the USA) with magnetic levitation. One reason why this would be so beneficial is that along with diesel engines the rubber tyres used on road vehicles represent another source of particulate matter air pollution.

Charging The Batteries.

Most battery electric buses use 'conductive charging', which is also known as 'direct wired contact' or 'direct coupling'. This well tried and proven system has traditionally involved plugging a cable into a socket on the vehicle. However other variants are being created which involve physical contact with an overhead power supply - but only whilst the bus is stationary at a dedicated charging point.

A variant of conductive charging sometimes sees the batteries being removed from the vehicle for recharging. If several sets of batteries are available then immediately replacing them with a fully charged set of batteries would mean that the bus could be back in service within minutes / without having to wait for the removed batteries to be recharged.

In addition to 'conductive charging' another way to charge the batteries (whilst they still remain in the bus) is via electromagnetic 'inductive charging'. This is further explored under the Roadway Power heading below.

Battery Electric Bus Examples.

Where battery technology has been proven viable (if given financial support based on environmental issues) is with small buses which are used on relatively short routes where the timetable has been arranged so that there is enough time between journeys for the batteries to benefit from either 'top-up' charging or being replaced with a fresh set of fully charged batteries. Note that with buses effectively "out of service" whilst their batteries are recharged or replaced so to maintain acceptable headways the fleet might need to be larger than it would have been had different solutions (motor or trolley buses) been chosen.

In the early 1990's Oxford, England, trialled a fleet of four electric minibuses. A report on their first 500 days of operation found that compared to similar diesel buses (and after taking account of extra emissions at the power station) there was:-

21% less carbon dioxide,
98% less carbon monoxide,
42% less acid gases,
93% less hydrocarbons, and
95% less particulates (the fine particles of soot which clog our lungs, causing lung disease).

Maintenance costs were comparable to diesels, but because of high design and development costs which were spread over just four vehicles they were twice as expensive to purchase. Their lead-acid batteries weighed-in at 2 ¼ tonnes, making them about 2 tonnes heavier than the regular diesel buses.

Services using these buses in Oxford ended when local government funding was withdrawn.

See caption for picture information. See caption for picture information.
Oxford, England. A long wheelbase 'Optare MetroRider' electric minibus 'tops up' its batteries while awaiting its next scheduled journey.
This was done by means of a cable from a roadside unit plugging in to a socket located on the bus.

Despite the environmental advantages the use of battery electric buses in British towns and cities is minimal. This is most likely because to Britain's cut-throat deregulated bus industry (where finance is seen to be the only thing which matters) such innovation does not make (financial) sense. That said, the British bus company which built the bus seen above suggests that thanks to the lower fuel and maintenance costs there are certain applications where electric buses can wash their faces financially - especially if the vehicles are leased rather than purchased outright - even without the grant aid of up to 80% of the additional cost that comes from the Government's Green Bus fund. The type of applications it has in mind include low milage, low speed routes in city centres and P+R services where there are daytime charging facilities, perhaps shared with battery electric cars.

One of the British conurbations which does use battery electric buses (in 2011) is St Helens, Lancashire. These are operated under the auspices of the Merseyside Passenger Transport Executive (Merseytravel) who have contracted out to private bus companies the operation of three free bus services which use a mix of mini and micro battery electric buses.

See caption for picture information. See caption for picture information.
One of the six St Helens Tecnobus Gulliver microbuses. Seen at Woodside Ferry Bus Station which connects with the Mersey Ferry.
Image & license: Colin Smith / The Geograph Project. CC BY-SA 2.0
Also used in St Helens are six of these battery electric Tecnobus Pantheon minibuses. Note the twin axle rear wheels.
Image & license: Quackdave / Wikipedia encyclopædia. Public Domain.

Small fleets of similar battery electric buses are also used in several towns and cities around the globe, where they are often seen to provide a very effective transport solution in pedestrianised and so called environmentally sensitive areas.

(Surely our entire 'living space' aka: the whole planet should be regarded as being 'environmentally sensitive' - not just a few streets in a city centre?)

See caption for picture information. See caption for picture information.
Bordeaux, France, running on a city centre service through narrow streets which despite its small size it still only just manages to negotiate. Amalfi, Italy. These Tecnobus Gulliver buses can carry up to 20 passengers, 10 of which are seated.
Image & license: Jensens / Wikipedia encyclopædia. Public Domain.
See caption for picture information. See caption for picture information.
Seen at the City Ferry terminal passengers board one of the 8 Tecnobus Gulliver electric microbuses which are operated by the Réseau de transport de la Capitale in the Old City district in Québec, Canada.
Image & license: zerojay (Jason Carter) / Flickr. CC BY 2.0
One of the Seoul Metropolitan Government (SMG) battery electric buses which are used on the Mt. Namsan circular routes, as detailed below.
Image & license: Wikipedia encyclopædia. CC BY-SA 3.0

Claiming it to be the first commercial all-electric bus service the Seoul (Korea) Metropolitan Government (SMG) in conjunction with Hyundai Heavy Industries and Hankuk Fiber has overseen the creation and introduction of some distinctively styled battery electric buses.

The electric buses on the Mt. Namsan circular routes are 11.05 metres in length (about 12 yards / 36¼ ft) and claimed to be able to travel as far as 83km (about 52 miles) on a single charge. Using high-speed battery chargers they can be fully charged in less than 30 minutes and have a maximum speed of 100 km/hr (about 62 mph). Four battery charges are being provided. They use high-capacity lithium-ion batteries and regenerative braking. The press release references collecting "energy generated from brakes when running downhill" which suggests that the route includes significant portions of hilly terrain which can be very beneficial for regenerative braking - but of course the inclines will drain the stored power even more quickly.

To reduce their weight and help maximise the distance they can travel between charges these buses make extensive use of carbon composite materials, instead of metal. They are also of a low floor design and are equipped with automatic slant boards for wheelchair users. To enhance their visual appeal and create an aura of being different they are shaped like a peanut and decorated with attractive designs symbolizing the Namsan Tower and landscapes of Mt. Namsan.

Initially December 2010 saw five of these buses being introduced, this was as part of a phased replacement of all 14 diesel buses on this service with the new electric buses. Their phased introduction was to ensure that if there were any teething issues then it would be possible to minimise the inconvenience which may be caused to passengers.

Also in Asia, the Chinese BYD eBus battery buses which use Iron-Phosphate have attracted attention of many transport operators planetwide. This is because BYD promote these buses as being able to travel 250km (155miles) on one charge, in heavy city traffic, with the air-conditioning switched on. Trials in Poland in 2013 suggest that even further may be possible, albeit not the 350km (217miles) which the public transport operator in Warsaw, the Polish capital city, has said that it needs from a battery bus to provide a full day's use from the one overnight charge. It is important to remember that these are new buses with new batteries - there is a need to see them in daily use for at least 5 years to know the likely longevity of their battery packs. By the time we reach 2018 there will be no shortage of real-world data, as 2,000 buses using these batteries are being introduced to the Chinese city of Shenzhen, 700 to the Dan bus company in Israel and small experimental fleets to many bus operators in about a dozen nations globally. This includes London.

See caption for picture information. See caption for picture information.
BYD battery electric eBuses started being evaluated in London in December 2013. These views show one of the buses. The batteries are stored inside the bus in two floor - to - ceiling compartments which are located behind the driver on both sides of the bus. The 3,000kg weight of the batteries reduces the overall passenger capacity from 96 (on the diesel Citaro buses which are also used on this service) to just 69 passengers. This reduction is to keep the vehicle's laden weight within the 18,000kg legal weight limit for twin axle buses.

The bus seen in these images is working on route No.507, which is a short (2½ mile / 4km) city centre service where the end-to-end journey time is only about 15 minutes. Buses on this route tend to make one return journey per hour, so even if used intensively they are unlikely to travel as much as 100 miles (160km) in the one day. This is significantly less than many buses travel on other services.

As an aside, whilst in Poland a BYD eBus set a new global distance record for a battery buses using public roads by travelling 310km (192miles) from Warsaw to Krakow on one charge. What is more, its batteries only consumed 69% of their total available charge, so theoretically in optimal conditions the remaining 31% of charge could have seen it travel about 430km (265miles). However, this was achieved at night, when the roads were empty, at an average speed of about 50km/h (30mph) and the batteries were still brand new.

Viennese Electrics

Another variant of battery electric midi bus can be found in the Austrian capital of Vienna where in September 2012 the first of 12 Italian EL Alé Rampini battery electric buses which have a capacity of 30 passengers started being used on two inner city routes. These 7.72m (a little over 25ft) midi buses are powered by lithium iron phosphate batteries which provide a total capacity of 96kW and provide enough energy for about 120km - 150km (74 - 93 miles) of travel. In addition to powering the vehicle's Siemens three phase synchronous motor, the batteries supply the onboard electronics, including winter heating and summer air conditioning. At each terminus they receive a top-up rapid charge lasting about 15 minutes. In addition they are given a full slow charge overnight.

As the images below suggest, daytime charging is achieved by the bus raising its roof-mounted tram-style pantograph to reach a dedicated pair of trolleybus-style twin overhead wires. Because both live and return feeds are required so the pantograph is split electrically into two sections.

Vienna has a large well established tram system and at this location its 600v dc power supply system is used to recharge the batteries. Since many of Vienna's trams use regenerative braking so often it is these buses (and not the trams) that end up benefiting. The buses also regenerate their own braking energy.

See caption for picture information. See caption for picture information.
Recharging the battery at the Schwarzenberg Platz terminus in Vienna. Images: Siemens press images at second link below.

More information and images can be found at these links which open in new windows:-

Important Safety Consideration - Whilst Recharging Via Direct Contact.

The system used in Vienna of frequent daytime (fast) top-up charging of batteries is becoming seen as one of the ways that larger buses can overcome the inability of batteries to provide enough power for a full day's use. It is important that any vehicle which is physically connected to an external source of electricity has robust isolation of its electrics from the body of the bus. Trolleybuses are double isolated and as part of the daily checks that are carried out before they enter public service (eg: braking system is OK, legally mandated external lights work, tyres are OK, etc) they also have an earth leakage test to ensure that their electrics are safe. Perhaps all buses which recharge onboard energy storage systems using physical connections to external sources of power whilst in the street domain should also undergo similar daily checks. It would be a terrible incident should the bodywork of a bus that is being recharged become live and either someone touching the bus or boarding / alighting it ends up being used by the electricity as a pathway to earth.

Fast Charge Batteries

One of the problems with batteries is that they risk being damaged if charged too quickly. Fast charging will also shorten their service life. By way of contrast, bus passengers do not want to be waiting even 10 minutes just so the bus can recharge its batteries! In an attempt to resolve this an American company has developed a type of battery which it claims is more suited to being fast charged.

Known as Altairnano (nLTO) these batteries comprise of nano lithium titanate, with the titanium being what makes the battery more able to accept rapid charging and discharging. However, nLTO batteries have a lower inherent voltage than other types of Li-ion battery, which leads to a lower energy density and the implication of this is that they are less powerful. As yet it is too soon to be sure of their viable service life, some estimates suggest six years, others think that it may be much longer. Or shorter. The reason for the uncertainty is that whilst conventional lithium-ion batteries can typically be charged about 1,000 times before they are considered no longer useful, laboratory tests suggest that nLTO batteries should be able to achieve over 16,000 charge and discharge cycles at rates up to 40 times greater than common batteries, and still retain up to 80% of their initial charge capacity. This helps explain why trials with real buses are needed to discover real-world results.

As of 2013 there are several experiments underway using nLTO battery powered fast charge buses. Included in these trials are some specialist overhead power supply charging systems, albeit with different implementation.

In America the first bus which uses these batteries is the Proterra EcoRide BE35. This is a 35ft (10.7 metre) 35 seat lightweight carbon fibre / glass fibre composite vehicle. These vehicles are used in an ever growing number of locations, albeit (so far) only in small numbers. They are recharged by stopping with the back of a bus below an overhead power supply unit so that a recharging arm can be lowered to make contact with conductors on the roof of the bus.

Also in the USA, the EBus Trolley comes in a 100% electric version which uses nLTO batteries. So far one transport company uses five of these 7 metre, 22 seat replica vintage trolley style buses. This is LINK Transit of rural Wenatchee, Washington State. Charging is also through the use of an arm which is raised from the back of the bus, and whilst therefore the theme is similar the physical equipment is different to that which the Proterra bus uses.

In Sweden the trails involve diesel hybrid buses in Umeå (which is in northern Sweden) and Gothenburg. Although the buses are called Plug-In Hybrids and often include electric plug motifs on their sides they are actually recharged by raising two small roof-mounted pantographs to reach an overhead power conductor that is somewhat like a metal bar a couple of metres in length that has been divided into two electrically isolated sections. This is known as a Bůsbaar (the word Busbaar has a small ring ° - as used in some languages - above the letter u) and was created by a Spanish company named Opbrid, in conjunction with some well-known railway industry component supply companies.

Once the bus has stopped below the Opbrid Bůsbaar the charging process is fully automated - its pantographs are raised for 5-10 minutes whilst the batteries receive a partial recharge, during which time the driver can remain in the bus. In addition, the batteries can be given a full charge at night.

Trials in Umeå commenced in 2011. There is an Opbrid Bůsbaar charging station at one end of the route and it serves two Hybricon Arctic Whisper fast-charge hybrid buses. These are modified Volvo 7700 series type hybrid buses which are capable of running with the diesel engine switched off. They have 100kWh Valence batteries which hold enough charge for up to three hours of fully electric operation, and the aim is that by constantly 'topping-up' the charge the buses will run in electric mode at all times, albeit with the reassurance that if there are any delays in reaching the Bůsbaar (eg: traffic congestion) then the bus will still have the diesel engine as a fall-back. With near arctic conditions in the winter and 30° heat in the summer, these trials in Umeå will also test the ability of the batteries to withstand a very wide range of climatic conditions. The trials are a collaboration between Hybricon (Sweden), Opbrid (Spain), e-Traction (Holland), Umeå Energi and Umeå city council. As an aside, electricity in Umeå is sourced renewably.

For Gothenburg three Volvo 7900 Hybrid Volvo buses were modified to be able to access an external power source. There is an Opbrid Bůsbaar at each end of the route and the desire is for the buses to travel as much as possible in battery electric mode. This is expected to be up to 7km, which equates to about 60% of the route, after which the diesel engine will be fired up and the buses will operate as normal diesel hybrids. According to Volvo there should be a reduction in fuel comsumption of 70%, although whether this just refers to diesel or also includes the electricity consumed when recharging the batteries is not stated. The buses will also use their diesel engines if they are delayed in traffic and do not reach their terminus with enough time to recharge their batteries before the next journey has to commence. Trials in Gothenburg commence in 2013.

In 2014 trials are expected to extend to Stockholm, the Swedish capital city, using eight buses.

More information can be found at these links which will open in new windows:
(This link includes a photograph of the first of Link's electric vintage trolley style buses).


See caption for picture information. See caption for picture information.
San Joaquin Regional Transit District (RTD) has two of these all-electric Proterra BE35 buses seen here below the "Fast Charging" station.
Image & license: SanJoaquinRTD / Wikipedia encyclopædia. CC BY-SA 3.0
Opbrid promotional photograph showing one of
Gothenburg's Volvo hybrid buses at a 300kW Bůsbaar charging station.


In May 2013 the Swiss city of Geneva launched a new experimental battery electric bus technology. What is different here than most battery electric systems is the use of flash charging, small batteries and full-size articulated buses.

This one year trial involves a single Hess Swisstrolley4 articulated electric bus which has been equipped with a small car-sized battery pack and serves just a few bus stops on a short route between Geneva Airport and Palexpo exhibition centre.

TOSA buses are charged from two different types of charging stations which are located at bus stops along the vehicle's route and at termini. The 400kW en route charging facilities are designed to provide a partial top-up in just 15 seconds, whilst passengers alight and board. The 200kW termini type charging facilities are deliver a 3 - 4 minute full recharge. To avoid sudden large drains on the urban electricity supply system the fast charging stations use capacitors rated at 3kWh to store electrical energy that has been slowly drawn from the 50kVA urban power grid. There are also bus charging facilities at the bus garage.

The power is transmitted to the bus via a laser-controlled moving arm located on the roof of the bus which connects to an overhead rail that is approximately 1m in length. This current collector is moveable in several directions, so that the vehicle benefits from a little leeway in its stopping position beneath the power rail. The system is designed for speed, so even as the bus is arriving at the stop the fixed overhead receptacle is being detected and the rooftop contact arm begins to align itself laterally to it. Once achieved the charging arm rises up from the bus and makes contact. After a safety check has ensured that a proper connection has been made with the stationary bus voltage is applied.

The flash-charging technology and the onboard traction equipment used in this project were developed by ABB and is optimised for high-frequency bus routes in key urban areas, carrying large numbers of passengers at peak times. The project is a collaboration between TPG; (Transports Publics Genevois - the Genevan public transport operator); OPI - as coordinator for industrial projects; SIG (Geneva power plants) for the power supply; and ABB.

More information can be found at these links which will open in new windows:

Note that Geneva already uses both (overhead wire electric) trolleybuses and trams, and concurrent with this trial is introducing a fleet of new trolleybuses which would be expected to still be in use in the 2030's and, given that trolleybuses often last 30+ years, the 2040's. The tramway has also only just received some new vehicles, one of which is involved in regenerative braking trials using capacitors.

TOSA is not seen as a replacement for trolleybuses, not least because the cost of installing a TOSA system (including the buses, charging stations and and electrical supply infrastructure) is expected to be comparable to a new trolleybus system. Its primary aim is to create a different way to convert diesel / other fossil fuel bus services to electric traction. The systems' reliance on batteries still represents a future liability.

If the TOSA system works well then the next stage will see a 9km diesel bus route being converted to TOSA buses, as part of a strategy for the cleanest possible urban air, this being something which requires the elimination of diesel buses from the city centre.

Ah, if only similar thinking applied here in Britain too!

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Tosa promotional image of the trial bus at a bus stop charging point.
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Part of a Watt system promotional image showing the charging arm on the bus plugged in to a roadside bus stop charging point.

Watt System

The French company PVI (Power Vehicle Innovation) is creating a fast charge system that can be retrofitted to existing single deck buses which will use capacitors to store the energy, with a 10 second 300 watt recharge being expected to provide sufficient energy for 600 - 800 metres of travel. In addition buses would be fitted with a battery pack which would provide back-up power, if needed.

Power transfer would be whilst calling at bus stops via a collector arm which slides sideways from a housing unit located on the roof of the bus into a socket located either on the roof of a bus stop shelter, as an integral part of the bus stop flag or as a free-standing totem pole.

More information can be found at this link which will open in a new window:

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Batteries + Capacitors = A Marriage Made In Heaven?

Although batteries are often used to absorb regenerative braking energy they are not best suited to this function, as they prefer slower more regular charging. By way of a contrast, capacitors are excellent for capturing large amounts of sudden and powerful bursts of electricity such as comes from regenerative braking, but less good at retaining sufficient energy for even medium time periods.

The Chinese saw the potential benefits of combining these two very different electrical storage media in ways which the Europeans and Americans failed to do, and in late 2009 introduced in the city of Shanghai a small experimental fleet of 10 such buses.

Early reports were very encouraging. Using lithium iron phosphate batteries and ultra-capacitors, it is reported that overnight charging of the batteries only requires 3 -5 hours (typically 4 hours, this being half that of other types of battery bus) and that their daytime range between charges is at least 160km (100miles) with the air-conditioner switched on, and as far as 250km (155miles) to 300km (186miles) with the air conditioning switched off. A driver on bus route No.825 revealed that on an average day the electric buses (s)he drives typically cover 154km (95miles) and consume about 170 kilowatts electricity, which makes running these buses cost about a third of a diesel engined bus. As an aside, these buses have a maximum speed of 130Km/h (80mph).

At the time of this 2013 update no information was available on these buses, which suggests that things may not have gone well with them.

Seeking The "Holy Grail" - Viable Alternatives To Batteries.

Over the years there have been several attempts to create workable, practical alternative solutions which feature electrically powered buses that can be used for a full day's operation - but without either overhead wires or heavy batteries. Two solutions which have been trialled, both require frequent recharging but only one seems to be finding favour.

Capacitor Energy Storage / Capabus.

Capacitors are solid state electric components that store energy. As technology advances so their properties and the terminologies used to describe them also change, with newer variants being called super-capacitor, ultra-capacitor, etc. It is beyond the scope of this page to explore the differences between the various types.

Some people add the prefix Capa before the name of a vehicle which uses capacitors. However since the use of capacitor powered vehicles is little known here in Britain so this term has not caught on in general terminology - and is not used on this page. Another reason for avoiding the capa prefix is because with a slight change of spelling it is possible to make a word which some people find offensive and suggests that something is of extremely bad quality / not value for money.

The principal constraint in the use of capacitors as alternatives for batteries is clearly understood once their energy density (amount of energy they can store and retain) is compared with batteries. Using weight as a comparator, an ultra-capacitor can store six (6) watt-hours per kilo, whilst a high-performance lithium-ion battery can store 200 watt-hours per kilo. (Some people say kilogram but when I was at school I was taught that with weight it is acceptable to drop the word gram).

In June 2005 "early stage" experiments commenced in the Chinese city of Shanghai with electric buses powered via super-capacitors.

Initial testing suggested that when fully charged the capacitors could be able to supply enough power for a bus to travel a total distance of 5km (about 3 miles & 200yds) at 44km/h (a little over 27mph), although for practicality it was proposed that recharging stations would be located approximately every 3 stops. As the images below suggest, recharging was by means of a scissors pantograph fitted to the buses' roof that made contact with an overhead power supply. For added benefit these buses featured regenerate braking, so that energy was recycled back into the capacitors - instead of just being lost as friction and heat via the brakes or rheostats.

For the initial testing the Shanghai Sunwin Bus Plant built four prototype super-capacitor electric buses, each one costing as much as 800,000 RMB, this being almost as twice expensive as a conventional Sunwin air-conditioned trolleybus. However in February 2006 it was reported that with all four test vehicles having broken down the opening of a proposed demonstration system had been postponed indefinitely.

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Prototype Shanghai capacitor electric bus at a recharging station. Note the use of scissors pantographs for power collection.
Despite it being of the utmost importance that other vehicles do not park illegally, blocking the recharging facility, this does happen.
Photographs and much information courtesy of Zachary Jiang.

However to properly evaluate the technology a further batch of super-capacitor buses was built, and on 28th August 2006 was placed into experimental service. These more extensive commercial trials involve Shanghai's route 11, which is a short circular trolleybus route of just 5.5km in length. This route is noted for lower levels of traffic congestion than the others, a constant passenger volume and high flow rate, with most passengers only travelling for three to five stops. This last point is significant, as it would mean that the passengers would be less likely to experience extended journey times from the frequent recharging.

The trials involve the capacitor buses travelling on the clockwise loop only, with conventional trolleybuses remaining on the counter-clockwise service. Furthermore, the trolleybus overhead for the clockwise circle is still being properly maintained, so that if the trials prove to be unsuccessful then conventional trolleybuses can return immediately.

Advance testing has shown that in theory if the air-conditioning is not in use then the capacitor buses should be capable of completing a complete loop on only one charge. However, to reduce the risk of a bus delayed in traffic congestion dissipating all its stored energy (and hence becoming stranded) plus to allow the air conditioning to be used there are in fact seven charging stations located around the loop.

These capacitor buses cost as much as 800,000 RMB each (approximately £6,600) a figure which includes the research cost. It is estimated that if the trials prove successful and they went into mass production then the cost will go down to 650,000 RMB; in comparison an air-conditioned Sunwin trolleybus costs only 400,000 RMB!

Hmmm, not a good start. Within a week of the trials commencing five out of the seven capacitor buses had already broken down, so to rescue the service some regular trolleybuses had to be reinstated. Apparently the problems have been blamed on the capacitors overheating under Shanghai's scorching heat. Even though it was officially autumn the weather was still hotter than had been expected. However by the end of September some of the failing capacitor buses had returned to service, with clock-wise services now being provided by a mixed fleet of capacitor buses and trolleybuses.

In addition, the capacitor bus drivers have been told that when travelling between route 11 and the garage they should use roads equipped with trolleybus overhead; this is because whilst theoretically they should be able to make the journey without recharging the high unpredictability of Shanghai's extremely congested streets makes it desirable to 'play safe' and not leave the safe haven of the overhead power lines. Although not planned as a regular feature in an emergency a capacitor bus can recharge from trolleybus overhead.

Reports from a visitor to Shanghai in February 2007 suggest that the trials are proceeding reasonably well. He also said that it is perhaps just as well that there are as many as seven charging stations along the loop, as buses traversing the loop are not always able to charge at every one of them. Apparently route 11 encompasses Shanghai's oldest historic relics and tourist attractions and tour buses often inadvertently park so that they block the charging points. He added that accurate docking is also essential because the charging process requires the charging facility to detect sensors on the super-capacitor bus - and this is only possible when it is stopped close to the footpath.

The visitor also reported that compared to normal trolleybuses the capacitor buses had slower acceleration and were smoother to ride - especially above 30km/h [20mph].

Perhaps the most significant issues (apart from the overheating when the trials commenced) is that because of the lack of recharging facility when returning to the garage bus drivers must drive to conserve the stored energy, which means switching off the air-conditioning, very modest use of the accelerator pedal, etc. Whilst in theory it is possible to recharge from the trolleybus wires the reality is somewhat more complicated. One issue is that with the trolleybus wires being located over the centre of the road so to reach them the capacitor bus would have to block the traffic flow. Another issue is that the trolleybus wires are often much higher than the charging stations, so that even when fully stretched the pantographs on the buses might not reach them.

click me for video Click the projector icon (or here) to see a video clip (in a new window) on 'youtube' showing a Shanghai super-capacitor bus raising its pantograph to charge the capacitors, plus other vehicles - including the trolleybuses operating in the opposite direction around the loop. The video was made by a visitor from Japan.

In connection with the 2010 World Fair (EXPO) being held in Shanghai 40 super-capacitor buses have been introduced for a special Expo bus service designed to also showcase Chinese technology. However things did not go well once the summer arrived, with the capacitors overheating causing some of the buses to break down. It seems that the capacitors work best when below 40°C, whilst when they reach 50°C an automatic safety lock is applied to the buses. Reports talk of dry ice being used in an attempt to keep the temperature down, however costing in excess of 500 Yuan per day per bus this represents an expensive solution. In addition, it has been found that the buses use more electricity when operating in higher temperatures, and therefore with the buses needing to be charged more often Shanghai Bus Co has also had to install more charging facilities along Expo Avenue. To allow for charging buses now spend 30 - 45 seconds at each bus stop.

On 27th January 2011 a capacitor bus which had been caught at some traffic signals on a busy but narrow two lane road somehow managed to create havoc by bringing down the trolleybus wires which it had been using to recharge. Exactly why remains unknown but it is possible that the bus driver starting moving without ensuring that the charging device had lowered. Witness reports suggest that the incident caused the twin overhead wires to collide with each other, resulting in a loud bang and lots of sparks. It is probable that the accident damaged the buses' capacitors, as afterwards it was unable to move away under its own power.

This incident caused significant traffic congestion and when other capacitor buses approached the area they spent so long in the traffic that they were unable to recharge, resulting in their stored energy dissipating and them becoming stranded as well.

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One of the Shanghai Expo 2010 super-capacitor electric buses recharging its capacitors and a close-up of the raised power collection equipment.
Image & license: Wikipedia encyclopædia. Public Domain. http://commons.wikimedia.org/wiki/File:ShanghaiExpo2010_Shuttle_Bus.jpg

By the end of 2012 three bus routes were using capacitor buses. These are the 11, 26 and Chongming 1. In December 2012 the super-capacitor buses on route No.26 started being upgraded with a newer, lighter and more powerful ultra-capacitor power pack, and by March 2013 12 buses (half its fleet) had been upgraded.

According to the Chinese Academy of Engineering the new power pack is a high-performance nickel-carbon capacitor which combines the functions of both battery and capacitor. The higher capacity is cited as being a result of a double layer of honeycombed active carbon and electrolyte that provides a larger surface area to generate electricity. Included in the benefits that these power packs provide are: a wider range of operating temperatures (between -40°C and +70°C), still working well after 10,000 charge / discharge cycles, being significantly lighter than earlier capacitor packs (down from 1.6 tons to 0.6 tons) and the maximum range before it needs recharging increasing from about 3 - 4km (a little under 2 - 2½ miles) to over 10km (about 6¼ miles). This last benefit means that on short routes one charge probably would cover an entire end to end journey.

Shanghai has 20,000 mostly diesel buses and as part of a desire to reduce urban air pollution is now looking at replacing between 1000 and 2000 of them with buses that use capacitors. Local officials see capacitor buses as being ideal for inner-city urban areas which do not require high speeds, plus in residential housing areas and as shuttle bus feeders between residential areas and local metro (subway) stations, these being some of the locations where their not emitting any tailpipe air pollution is of the greatest benefit.

Even though it is only 10 minutes the time spent charging - especially if a bus is running late according to its scheduled timetable - does represent an Achilles heel (ie: nuisance / problem). The optimal solution would be to fit these buses with trolleypoles, as then they could recharge from trolleybus wires whilst travelling - and would be able to easily perform a full day's work without delays. In addition, the overhead wiring would only be needed for relatively small segments of the route, ie: there would be no need to electrify the whole route. In-motion recharging would also solve the traffic congestion problems caused by capacitor stopping to recharge - as described at the third link below

Some links (which open in new windows) to further information:-

Confusing Publicity Data.

A Chinese company involved in building (or promoting) the capacitor buses is using confusing data which suggests that they use 40% less energy than trolleybuses. Whilst they cite regenerative braking and the lower vehicle weight of the newer buses as being the reason, by not specifying the exact vehicle types involved (ie: when built, whether rigid or articulated, etc.,) it becomes impossible for the non-critical reader to validate their comparison. It is assumed that they mean a 1950's era articulated trolleybus which lacks regenerative braking and was built with a heavy metal chassis and body, plus thick (hence weighty) window glass. If so, then just about any present-era electric bus, whether trolley or capacitor, will be significantly more energy efficient. Even more so if (like all their capacitor buses) it is of a shorter rigid (ie: not articulated) type that features a specially designed lightweight body and internal fittings, plus uses regenerative braking!

The Gyrobus.

Shanghai's trials with super-capacitors are reminiscent of a system trialled in the 1950's with what was known as a gyrobus.

The gyrobus concept was developed by Oerlikon (of Switzerland), with the intention of creating an alternative to battery-electric buses for quieter lower frequency routes where full overhead wire electrification could not be justified. The buses were equipped with a large flywheel that spun at speeds of up to 3,000 rpm, gradually slowing as the stored energy was used to provide electricity for the buses' traction motor. Power for charging the flywheel comprised of three phase AC which reached the buses via three roof-mounted booms which contacted charging points located as required / felt desirable (eg: bus stops en route, at termini, etc).

Fully charged a gyrobus could (typically) travel as far as 6km on a level route at speeds of up to 50 - 60km/h (depending on vehicle batch as top speeds varied from batch to batch) The installation in Yverdon (Switzerland) sometimes saw vehicles needing to travel as far as 10km on one charge, although it is not known how well they performed (or otherwise!) towards the upper end of that distance. Charging a flywheel took between 30 seconds and 3 minutes, and in an effort to reduce the time this took the supply voltage was increased from 380 volts to 500 volts. It can only be speculated whether such frequent delays would have been acceptable had the gyrobuses survived - in commercial service - into the modern era. Especially on longer routes where several charging stops could have been required or on busy, heavily trafficked roads.

In all three locations used gyrobuses in full commercial service, these being Yverdon, Switzerland, Gent, Belgium and Léopoldsville in Zaïre. Whilst the technology worked reasonably well for various reasons none of these systems lasted for more than seven years - at most.

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Gent, Belgium gyrobuses Nos 1453 and 1452 at an intermediate charging point. Although not seen here the photographer suggests there were also two auxiliary contact arms that moved sideways from the gyrobus to make contact part way down the post.
Image dated to 24 August 1958 and is courtesy of Noel Reed.
Looking from the front towards the back inside the only extant gyrobus which is at the Flemish tramway, trolleybus and bus museum in Antwerp, Belgium.
It is assumed that when in normal service the equipment seen in the middle of the bus would be covered with a parcel shelf.
Image & license: Vitaly Volkov (user kneiphof) / Wikipedia encyclopædia.
CC-BY-2.0   http://commons.wikimedia.org/wiki/File:Gyrobus_G3-interior1.jpg

Additional Gyrobus Information.

The gyrobuses used an asynchronous three-phase electric motor with condensers fitted on a common shaft. The motor was built on to a flywheel which (on the demonstrator) was 1.6m in diameter and weighed 1.6 tonnes. This was housed in an enclosed hydrogen-filled air-cooled casing.

To obtain tractive power condensers would excite the flywheel's charging motor so that it become a generator, in this way transforming the energy stored in the flywheel back into electricity. Vehicle braking was electric and some of the energy was recycled back into the flywheel, thereby extending its range.

The demonstrator was first displayed (and used) publically in summer 1950, and to promote the system this vehicle continued to be used for short periods of public service in a myriad of locations at least until 1954.

The first full commercial service began in autumn 1953, in Yverdon, Switzerland. However this was a route with limited traffic potential and although technically successful it was not commercially viable. Services ended in late autumn 1960, and neither of the two vehicles (nor the demonstrator) survived..

The next system to open was in Léopoldsville in Zaïre (formerly the Belgian Congo and currently known as Kinshasa in the Democratic Republic Congo). Here there were 12 vehicles (although apparently some reports erroneously suggest 17), which operated over four routes with recharging facilities being provided about every 2km. These were the largest of the gyrobuses, being 10.4m in length, weighing 10.9t, carrying up to 90 passengers and having a maximum speed of 60km/h (about 37mph).

However all did not go well, with there being major problems related to excessive "wear and tear". But it seems that a significant reason for this was because the bus drivers often took shortcuts across unmade roads, which after the frequent heavy rains became nothing more that quagmires and marshes. Other problems included breaking gyro ball bearings and high humidity resulting in traction motor overload. The system's demise however came because of high energy consumption. The bus operator deemed that 3.4kWh per km, per gyrobus, was unaffordable, so closure come in the summer of 1959 with the gyrobuses being dumped next to bus garage and left to rust.

The third location to use gyrobuses commercially was Gent, Belgium. Three gyrobuses started operation in late summer 1956 but instead of being the first of a proposed multi-route network they did not last very long, being withdrawn late autumn 1959. It seems that the operator was blaming them for being unreliable "spending more time off the road than on" plus that their weight damaged road surfaces. They were also seen as being energy hungry, consuming 2.9kWh per km - compared to between 2.0kWh per km and 2.4kWh per km for much larger trams that carried several times the numbers of passengers. One of the three gyrobuses has been preserved as an exhibit at the Flemish tramway, trolleybus and bus museum in Antwerp, and it is sometimes displayed as a curio (or even used to carry passengers!) at Belgian exhibitions, transport enthusiasts' bazaars, etc.

In 1985 it was used in the Belgian town of Ostend as part of the 100 year celebrations of the Belgian Vicinal light railway system. Photographs of this gyrobus at a charging station and at the museum (including several views inside it) can be found at this page at the Wikipedia encyclopædia Commons (link opens in a new window):- http://commons.wikimedia.org/wiki/Category:Gyrobus_G3

Much of this additional information was sourced from the January / February 2005 issue of "BusesWorldWide" as issued by the organisation of the same name "http://www.busesworldwide.org (link to an external site which opens in a new window).

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Roadway Power / Gapbus.

In addition to conductive charging another way to recharge the stored energy (batteries / capacitors) is via electromagnetic inductive charging.

Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The major advantage of the inductive approach over conductive charging is that there is no possibility of electrocution as there are no exposed conductors.

Inductive charging is well known for low power domestic electrical items - such as toothbrushes and wet/dry electric shavers - where the reasons why it is favoured include that the battery contacts can be completely sealed to prevent exposure to water.

However there are some drawbacks with inductive charging; these include that it has a low efficiency where much energy is lost in heat and that it is a relatively slow way to charge batteries - and whilst this is not an issue for toothbrushes and shavers as they can be left on charge at all times§ - it is for buses and other transports which generally need to be in service as much as possible during their working day.

§ The cumulative effect of millions of householders leaving things switched on all the time poses significant environmental challenges, especially when the electricity is sourced from fossil fuel power stations.The overall amount of extra energy that is consumed often requires extra power stations to be brought onstream, this being a cost that increases the cost of the electricity.

However showing much promise as potentially being more suitable for road vehicles is a variant of this theme known as resonance charging (or sometimes electro dynamic induction). This is claimed to be 80-90% efficient. A very basic explanation of how this works is that the energy source features an oscillating magnetic field from which a ring coil on the receiver collects its energy. The closer the ring coil is to the source of the oscillating magnetic field, the better the efficiency.

Buses which collect power using the various types of non-physical under-road induction have been dubbed 'gapbus' - because of the air gap between the road surface and the vehicle.

Stationary Vehicles.

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An induction charged 7.5 metre (24.5') battery electric midi bus in Turin, Italy. Depending on various sources of information there are either 28 or 30 vehicles of this type operating in several Italian cities, with there being 22 in Turin (purchased 2002) and 8 in Genoa (purchased 2000 - although some sources suggest that the entire fleet dates from 2002).
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Closer views of the induction charging facility. The bus must stop accurately so that the charging plate can be lowered over the correct portion of roadway.

This link also references these trials, and more

These trials use Conductix-Wampfler IPT® (Inductive Power Transfer) technology. This is an energy transfer system for electric vehicles that works by magnetic resonance coupling. The system consists of a primary coil in the road, which is connected to the power grid, and a pickup coil fitted beneath the vehicle.

By 2012 induction charging in Turin and Genoa was considered mature enough for trials using larger buses to begin. So in autumn 2012 induction charged battery electric buses trial using standard sized 12 metre buses began in the Dutch city of s’Hertogenbosch (Den Bosch).

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A electric bus in the Dutch city of s’Hertogenbosch (Den Bosch). The plug logo on the side of the bus is a marketing tool - the bus collects electricity through induction and not cables.

Images: Conductix-Wampfler press release about the commencement of the Dutch trials.
(Link opens in a new window and requires an Acrobat compatible pdf / portable document viewer.)

The plan is for the bus to travel 288km (179miles) per day without having to stop for prolonged periods or return to bus garage to recharge its batteries. The batteries will be fully charged overnight and topped-up by 10-15% as necessary and as possible over the course of the day.

These trials are a collaboration of several partners, including the city of s’Hertogenbosch (Den Bosch): Bluekens Bus & Truck (building and supplying the bus), Conductix-Wampfler (supplying and erecting the inductive charging solution), Heijmans (installing the charging points), Arriva (driver training and bus operation) and Enexis (connection of the charging system). More information can be found at this link (which will open in a new window):

In 2013 similar trails are expected to commence on a 12½ mile bus route in Milton Keynes which operates every day of the week and will involve three charging stations. Whilst only seven diesel buses are needed to operate this service the extra 10 minute charging session before each journey means that eight battery electric buses will be required. The hoped-for aim of these charging sessions is the replenishment of 2/3rds of the energy consumed whilst traversing the bus route. This technology trial will be a collaboration of eight different businesses who have signed-up for five years. More information can be found at these two links (which will open in new windows):


In autumn 2008 a major global transport vehicle manufacturer announced proposals for an induction system which would be installed under the road along (much of) the transports' route, with the vehicles drawing power as they travel over it; and also storing their own regenerated braking energy to lower the overall demand on the power supply system when the vehicle is accelerating from rest and permit operation at locations where there is no power supply. Although primarily promoted as being for trams it was stated as being suitable for electric buses too.

The company is Bombardier and the technologies are known as Primove (induction power supply system) and Mitrac (capacitor energy storage system).

The Primove buried inductive loops are eight metres in length and fed by an inverter which transforms 750v DC into 200 kHz AC. They are only 'live' when the transport is over them. The transmission efficiencies of 90% - 95% are claimed to be only 2% less than those achieved with physical contact systems. With trams they are located at tram stops and on uphill gradients. When away from the power supply the trams are powered using the Mitrac energy storage system.

With trials using a modified tram on an 800m route in Augsburg, Germany having proven successful, May 2013 saw the commencement of a further round of trials, this time using buses, in Braunschweig, Germany. Known as Project EMIL these trials involve Primove charging pads which have been placed at specific locations where the buses can collect power whilst stationary.

Emil involves several buses and a service vehicle. Different reports suggest that there will be either two or four buses. They will run on a 12km loop service around the city that has a typical journey duration of 37 minutes. Buses will receive a full charge overnight plus a 10 minute top-up charge between journeys whilst at the route terminus (the main railway station) plus 30 second booster charges whilst calling at several intermediate bus stops en route. The idea is to see if it is possible for buses on route M19 to provide a full day's service whilst carrying small Li-Ion battery packs which do not impinge upon the vehicles' overall passenger carrying capacity.

This link (which opens in a new window) leads to a page on the transport operators website that explains more. Although it is the German language website there are several free online translation services which will facilitate seeing an English version.

The first of the buses arrived late 2013. This is a 12 metre vehicle which will only use the 200kw charging pad at the railway station. Passenger services are using this bus are expected to commence in February 2014. The next bus will be an 18 metre articulated vehicle and because of its higher power requirements it will use all the charging pads.

These links (which open in new windows) include a German-language newspaper article about trials and a Bombardier press release which also includes some photographs of the specially liveried 12 metre vehicle. Some of the photographs show it in the German city of Mannheim.

In winter 2013 / 2014 trials using Primove technology in an extreme cold weather climate will be conducted on a private test track on Île-Sainte-Hélène, Montréal, Canada. The aim is to discover how the technology copes with some of the harshest conditions that can be expected in an inhabited area.

In 2014 further trials with Primove induction buses are planned for the German city of Mannheim and Belgian city of Bruges.

Other Induction.

Other trials using induction powered battery-electric buses are underway using the US-based Wave system. WAVE is an acronym for Wireless Advanced Vehicle Electrification. The technology was developed at Utah State University although it is now being marketed by WAVE inc., which is a spin-out company. WAVE mostly uses 50kw charging pads, although their first electric bus, which operates shuttle services within the Utah State University campus, uses a 25w charging pad. This vehicle is nicknamed the Aggie Bus.

Included in their planned trails which are expected to commence in 2014 are:
* 10 Chinese BYD battery electric buses which will be fitted with WAVE's charging system and used in the Long Beach area of Los Angeles, Califormia.
* Several services in Ogden City, Utah serving Weber State University and McKay-Dee Hospital
* The replacement of a diesel vintage trolley styled bus with one that uses electric propoulsion and WAVE recharging in Monterey, Califormia.

This link (which opens in a new window) leads to the WAVE website.

Whilst it is hoped to be being fair to all organisations which are trialing new technologies and at least mention them, there always remains the possibility of lower profile developments to remain unknown.

Moving Vehicles.

Much more challenging than with stationary vehicles is the ability to supply energy using induction to a vehicle which is in free motion on a road and to ensure that it works even with a constantly changing gap between the vehicle and the road surface.

The concept is not new, as in the early 1990's proof-of-concept trials were carried out with a 35 seat Roadway Powered Electric Vehicle (RPEV) at the University of California Richmond Field Station. The trials saw the burying of power conductors under a 700ft (about 213m) test track and an operational RPEV which featured a needle dial so that as the vehicle travelled along the road the driver could see the strength of the charging current being received and accurately locate the vehicle above the under-road power supply.

The RPEV system was shown on television as being able to draw enough power from below the road surface that it could also roam away from the power source, so that perhaps a main road serving many bus routes would be electrified but they would be able to make short scheduled detours in battery electric mode. However despite the technology still being in need of refining before it would be ready for full commercial exploitation once these trains had been completed the project became stalled. Perhaps this was because between 1992 and 2000 the USA had a President who was a member of the oil industry - if so then the lack of further development is not at all surprising. A report on these trials can be bought from this link which opens in a new window:-

But whilst the American leadership did everything it could to roll back further development in electric transport technologies (with increased use of fossil fuels being the primary aim) further development work in Korea resulted (in March 2010) in a more advanced variant of the RPEV being launched in Seoul, Korea. Known as the On-Line Electric Vehicle (OLEV) the technology is being tested on a 2.2km route at Seoul zoo which is served by a 'road train' that had previously been criticised for its diesel exhaust fumes.

Researchers at KAIST (Korea Advanced Institute of Science and Technology) succeeded in refining the technology so that it offers power transmission pick-up capacity of 62kw, at up to 74% efficiency, over an air gap between the road surface and the bottom of the vehicle of around 12cm - 13cm (about 5").

In Seoul zoo the OLEV train travels along 2.2km route which is equipped with four sections of under road power supply equipment.

Sections 1, 2, and 3 are each 122.5 metres in length, whilst Section 4 is just 5 metres in length.

This makes for a total length of subterranean power supply cables of 372.5 metres, which is just 16% of the 2,200 metre route.

The OLEV trail 'train' at Seoul Zoo comprises
of one engine and three passenger carriages.
See caption for picture information.
Image: Kaist publicity material at the 'kaist.ac.kr' link below.

If the technology proves viable it will be installed along the bus lanes in many city streets, as since buses account for 30% of all city traffic so electrifying them is being seen as providing a significant impact in reducing urban air pollution. Kaist estimate that only about 20% of a route's entire length would need electrifying, although if evidence from the OLEV is correct then this would include bus termini so that buses could be recharging their batteries whilst stationary between journeys.

A different press release talks about an experimental plan which would see power strips between 20cm (about 8") to 90 cm (about 35") wide and perhaps several hundred metres long being built into the road surface along about 10% of the entire road system of an urban area with small batteries about a fifth the size of the batteries used in existing battery vehicle storing enough energy for about 50 miles (about 80km) of pure battery power.

The next stage of the development of OLEV technology is for a bus service to use it. This is underway in the Korean city of Gumi. The news.kahn.co.kr article linked below suggests that the trials will involve a bus (similar to those used on the Namsan area seen above) travelling on a 12km (about 7½mile) route making about 10 journeys daily. Although there is additional information the online translation from the news.khan.co.kr linked below is not robust enough to understand exactly what is being said.

However information from printed paper sources suggest that the trails involve two battery-electric buses similar to those used on the Mount Namsen service and because of the length of the power conductors there is a concern about stray current leakage which would breach European Union Electromagnetic Compatibility regulations, and therefore this system would be deemed as unsuitable for use in Europe.
Further information can be found at these links which open in new windows:-

US OLEV Trials Falter

In 2011 it was announced that in 2013 the Texan city of McAllen would be using 3 OLEV buses on a 10mile (16km) route. This would be in conjunction with the OLEV Technology Corporation which is based in Massachusetts and is a venture company in which KAIST has a 30% share. The corporation has the sole license to commercialise OLEV technology in the USA. However due to financial reasons this scheme was cancelled in October 2012. These links (which open in new windows) explain more:

Physical Contact Roadway Power.

In 2000 a "roadway power" technology which was specially designed for buses was tested with several electric buses in the Italian city of Trieste. Unfortunately however the trials coincided with a change of local government - and whilst it seems that the outgoing politicians were keen to see the system expanded to more routes the new politicians were not.

Perhaps at least in part this was because the trials were on one of the cities' busiest bus routes and there was some disruption, especially when it was being installed.

See caption for picture information. See caption for picture information.
A demonstration section of the experimental 'Stream' road surface power trackage and collection skate as seen at the 1999 UITP exhibition in Toronto, Canada. On this display version the red light on the skate illuminates to demonstrate that power (low voltage in this instance) is being received. Stream road surface power trackage in Trieste.
Image & license: Luca Fascia / Wikipedia encyclopædia. CC BY-SA 3.0
See caption for picture information. See caption for picture information.
These two images include a view of the power collection skate as seen from inside the bus. When the bus is in motion the skate tracks the power trackage by wandering from side to side under the bus.

Images above & left: the vehicle manufacturers' publicity material.

The technology was based on twin metal conductors located on the road surface. To ensure safety and avoid the possibility of electric shock the conductor that carried the live power was split into short sections that would only be live when the bus was actually over them. This system only ever existed in experimental form, however one specific technical problem which the Trieste trials identified was that the metal (of the power conductor) on the road surface could be slippery, especially when wet.

Since these trails marketing of this system ceased and in 2009 it was replaced by a different technology which (so far) has only been tested with trams, although its promotors suggest that it is suitable for buses as well.

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The case for NOT using Ultra Low Sulphur "clean" Diesel fuel
and Regenerating Particulate Traps

Additional information gratefully obtained from the Electric Tbus Group www.tbus.org.uk (link to an external site which opens in a new window)

Why even so called "clean diesel" is still an environmental disaster!

Diesel exhaust has been found to contain over 41 different toxins, many of which form part of the particulate. These toxins are still present in "clean diesel" powered vehicles which use Ultra Low Sulphur Diesel fuel (ULSD) and Continuously Regenerating Particulate Traps (CRT). Vehicle emissions have their greatest impacts on those directly exposed, i.e. pedestrians, transit users, those living on busy transport corridors. Electric buses produce no in-street emissions. Unless all the emissions diesels release into the surrounding air can be completely eliminated, the diesel can never be competitive with an electric bus in terms of emissions impacts. This should not imply that efforts to reduce diesel emissions are wasted. Since diesel engines will continue to be used for a variety of purposes, every effort should be made to make them as clean as possible. But one needs to realize that making an internal combustion engine cleaner does not make it a universal substitute for an electric vehicle.

So called 'cleaner' diesel increases greenhouse gases!

Data from the British Freight Transport Association (FTA, 1999) indicates that the production of Ultra Low Sulphur Diesel fuel (ULSD) [at refineries] results in some 20 tonnes more CO2 equivalent than the production of regular diesel. Indications are that powering a vehicle with ULSD requires more fuel than with regular diesel, meaning that, while some emissions may be reduced, the amount of CO2 released by the vehicle is likely to be greater

See caption for picture information. See caption for picture information.
In Lyon, France trolleybus route No. 6 operates over some narrow, twisting, hilly roads which are unsuitable for full-size buses so uses a fleet of half a dozen specially constructed 27 seat (53 passenger total capacity) 9.7m long, 2.4m wide midi-trolleybuses. The significance of this is that in the bus building industry (as in many other industries) the cost per item (bus in this instance) is quite a bit higher when only a few are built compared to large productions runs when a lot are built. Yet despite this it was found more desirable to use trolleybuses than fossil-fuelled buses.

Using Continuously Regenerating Particulate Traps Has
Serious Negative Environmental Repercussions Of Global Proportions!

The environmental benefits of exhaust after-treatment devices was recently called into question when researchers discovered heavy metals from catalytic converters embedded in the ice in remote regions of Greenland. A European Commission study found that vehicle exhausts actually erode the metals in these devices, ejecting microscopic particles into the air. Some of these metals have also been linked to asthma and lung conditions. Researchers noted that some of these particles are soluble, meaning that they can be readily absorbed by vegetation and enter the food chain. New Scientist magazine concluded that this is already a problem is of global proportions.

Scientists Say The release Of Heavy Metals From Exhaust Treatment Devices
Is A Global Problem That Also Stands To Threaten Human Health.

See caption for picture information. Nancy, France. These innovative three-section double-articulated TVR trolleybuses were designed to give a tram-style ambiance to rubber tyred road vehicles - this being something which they have achieved admirably.

The TVR concept allows for the vehicles to operate in either driver-steered mode (as regular trolleybuses) or pseudo-tram mode using a proprietary guidance system which is totally independent of the vehicle's propulsion system. Unfortunately some unenlightened transport pundits have quite incorrectly used this latter feature to suggest that ALL trolleybuses are 'guided' (aka self steering) buses.

Worse still, they are hoodwinking the general public into believing this blatant untruth.
click me for video
Click the projector icon (or here) to see a 14 second video clip named 'Nancy-unguided-S-bend320.mpg' showing the TVR making this 's' shaped manoeuver (plus hear the above photograph being taken - oops!).

So called 'cleaner' diesel fuelled vehicles still emit lung-damaging particulates!

Trap devices such as the CRT primarily focus on reducing the amount of particulate matter that diesels spew into the surrounding air; there is also some concurrent reduction in hydrocarbon emissions. Some traps claim to reduce particulate emissions by up to 90% in tests, although their performance in real-world conditions may vary considerably. In any case, some particulate is still released, and because "clean" diesel particulate is so much finer than that from conventional diesel engines (and invisible to the naked eye) these toxins have an easier time entering our bodies and penetrating the linings of the lungs. There is no safe level of exposure. German researchers insist the toughest diesel emission standards are not tough enough. (PM10 particles with mass less than 10 microgrammes). The Daily Mail of December 27, 2000 reported that such particulate was found deeply imbedded in the lungs of very young children, in particular children who lived in homes located along busy roads. This particulate is believed responsible for an increase in lung disorders and asthma and has also been linked to heart disease. The incidence of asthma in children under five has doubled in Britain in the last ten years and is on the rise in many other countries. There is also strong evidence for a causal link to cancer, although the research as not (yet) established this beyond doubt..

In spite of trap devices Oxides of Nitrogen (NOx) still form a major component of diesel exhaust and pose significant health risks. Oxides of Nitrogen essentially comprise a mixture of Nitric Oxide (NO) and Nitrogen Dioxide (NO2). NOx is transportation's principal contributor to urban smog and poor air quality. In combination with the moisture in the lungs, Nitric Oxide (NO) forms nitric acid. This acid results in inflammation, leading to chronic respiratory problems. Eventually, all Nitric Oxide emissions are converted to Nitrogen Dioxide (NO2) in the atmosphere. Nitrogen Dioxide is a corrosive and very poisonous gas. At concentrations above 150 ppm it leads to death. The CRT (Continuously Regenerating Trap) uses a catalyst to convert Nitric Oxide in the exhaust stream to NO2 because it needs the NO2 for a reaction that 'burns off' particulate matter and hydrocarbons. There is a strong likelihood that the proportion of NO2 in the NOx emitted by CRT equipped engines operating in real world conditions will be greater than is the case with non-CRT equipped diesels. If so, it would put a greater quantity of the more poisonous constituent of NOx emissions directly into the airways of pedestrians, transit users and area residents than would be the case with conventional diesels, where the a slower process of oxidation in the atmosphere would be required to yield the same quantity of NO2. In other words, there is every possibility that ULSD in combination with the CRT may actually intensify some of the health effects of diesel exhaust.

See caption for picture information See caption for picture information.
MBTA trolleybus operating near Harvard Square in Cambridge, Massachusetts (USA).
The offside door is used at Harvard station in the bus tunnel.
Image & license: ArnoldReinhold / Wikipedia encyclopædia. CC BY-SA 3.0
Trolleybuses make light work of steep hills - San Francisco, USA.

The case for NOT using fossil fuel engines which meet "Euro 4" etc., standards for urban bus services.

Being introduced in 2006 are regulations called "Euro 4" which has the aim of enforcing a reduction in the output of harmful particulates and NOx nitrous oxide from motor bus exhaust (waste) gases. Euro 4 can be seen as a stepping stone to "Euro 5" which in 2009 will cut NOx pollution (but not particulate emissions) even further. Both regulations will apply to new buses only - existing vehicles can continue to operate with their older even dirtier engines.

Of course it is right to use the propulsion systems which create the least pollution - and for rural areas where the cost of electrification plus maintenance of the infrastructure would simply render the bus service uneconomic then by using sustainably sourced biofuels in engines which meet the "Euro 4" and "Euro 5" standards is a logical solution. But there really is no justification for using the "less dirty" option for urban services - not when a clean alternative choice exists.

However apparently 'clean' Euro 4 / 5 diesels may appear to be it need be remembered that the supposed performance is measured on new vehicles / engines in tip top condition on test cycles. No matter how clean they are when new, experience with existing engines suggests that as they age their emissions performance will deteriorate.

Whilst optimal regular maintenance will help keep the engines cleaner this reflects extra expense and "downtime" spent in the garage instead of being on the road earning revenues. The fleet will also need to be larger to cover for the extra time spent in the garage.

More information.

In an effort to meet the new regulations motorbus suppliers are following two competing routes. These are known as EGR (Exhaust Gas Recirculation) and SCR (Selective Catalytic Reduction).

EGR uses an EGR cooler to reduce the temperature of a controlled amount of exhaust gas which is then recirculated into the engine to achieve lower combustion temperatures. thereby reducing nitrogen emissions at source. Around 10% of gases are recirculated for Euro 4, this is expected to increase to 25% to meet Euro 5.

Instead of modifying the engine SCR is an exhaust gas after-treatment whereby a mixture of 32.5% urea and deionised water (known as AdBlue) is injected into the exhaust gases where the heat of the waste gases transforms it into ammonia and carbon dioxide. The ammonia then reacts with the nitrogen dioxide in a catalytic converter to form harmless nitrogen gas and water vapour. A clean up catalyst then converts any residual ammonia into nitrogen gas and water vapour.

On urban buses the waste gases must also pass through another catalytic converter which is fitted in front of the SCR catalyst. This is to ensure that the SCR system functions under operating conditions with low exhaust temperatures.

In cold climates the AdBlue starts to freeze at -11 deg C and until the engine is running and giving off heat the effects of the exhaust filtration system will not be felt. Vehicles which operate in climates where such temperatures are frequent can be equipped with heated Adblue tanks.

According to SCR advocates for the Euro4 standards urea consumption is 3-4% of diesel so 40 litres of Adblue should be sufficient for about 1000 litres of diesel. For Euro 5 it is expected to be about 5% of diesel consumption. The liquid itself is claimed to be low-toxic, non flammable, not explosive and not pose any known human health risk. Unlike fuel oil there are no special restrictions regarding its transport or handling. The urea consists of ammonia and carbon dioxide and the production process involves airborne nitrogen reacting with hydrogen from a source such as natural gas.

There are no such things as clean diesel vehicles. Just "less dirty".

Why biodiesel is not an alternative solution for urban bus services
(and maybe not elsewhere either).

Many of these comments also apply to ethanol, which some bus operators see as a 'green' (sic) solution.

As oil prices soar and some people feel a desire to source fuel from renewable sources so there is increasing interest in what is known as "biodiesel".

Biodiesel is usually sourced from vegetable oils derived from plants which are specially grown as a crop in a field, although it can also be sourced from animal fats too.

The theoretical advantage of biodiesel is that it should be CO2 neutral, because as much CO2 should be taken up growing it as is produced when it is burned. However, if the crop is heavily fertilised using fertiliser that has itself been sourced from fossil fuel, and if a lot of fossil fuel is used harvesting, transporting, converting the crop to biodiesel etc., (ie; the normal sorts of agricultural usage of fossil fuels) then biodiesel may still be a net emitter of CO2.

Sourcing Problems - with potentially disastrous ecological consequences.

It is also important to note that if the crops from which the biodiesel has been sourced would have been grown anyway (eg: wheat & maize [corn], for human or animal consumption) then using them for liquid fuels does not provide any ecological benefit - indeed if the result is a shortage of food and a consequential increase in food prices then there is a significant disadvantage, especially to the less financially wealthy members of our human family (who might then not be able to afford to feed themselves adequately) and to farmers who may not be able to afford to feed their livestock.

Reports from some countries suggest that people are going hungry because they can no longer afford to buy foods as the crops are being sold at higher prices for conversion into fuel. Other reports talk of gangsters stealing farmland to grow these cash crops, which frequently leaves the displaced farmers suffering severe hardship (eg: financial poverty, inability to afford to buy food, housing, healthcare). There have also been instances of corruption with the issuing of false certificates claiming that the crop has been sourced following the highest environmental standards - when it has not.

There is also no point in tearing down the Amazonian / equatorial rainforest (something else which is happening) - just to grow crops for fuel - as this sort of deforestation is very much a disaster of the worst possible magnitude. One reason why these ‘rainforest replacement' plantations are less than desirable is the loss of biodiversity (ie: a wide range of types of plant which support many different animals are replaced with one type of tree which is not beneficial for many types of animal life). Indeed it seems that this loss of habitat for the animals which live in the rainforests is leading to a situation whereby one species of monkey is now actively threatened with extinction. It may be that other ‘lower profile' / ‘less well known' animal species also face a similar threat, however the media reports do not state this.

It must also be remembered that the rainforests are our planets' lungs. Without them we (mankind) might have some more fuel, but we effectively will be signing the death warrants (through asphyxiation) of just about every oxygen breathing living being on the planet.

The ideal crops to replace when growing crops for conversion to liquid fuels.

Although somewhat off-topic for this page it must be pointed out that there are some cultivated crops which are already grown on a 'mono-culture' basis that are not at all essential to human life that could be replaced (with crops grown for conversion to liquid fuels) without seriously affecting the global ecology, bio-diversity, etc.

These crops are those which are often converted into both 'legal' and 'illegal' narcotic drugs, such as tobacco, et al. Indeed, there could be many societal as well as environmental benefits by persuading farmers to switch away from growing plants for narcotics to growing plants for liquid fuels (and perhaps other crops which offer mankind some 'useful' purposes, eg: foods, medicinal herbs, hemp - which can be used for paper, food, string, liquid fuel and more - but not narcotics!)

Perhaps the principle constraint to this would be that plants grown for narcotics tend to be very profitable, but (hopefully) as long as there are equal (or even greater) financial (etc.,) rewards for growing plants for conversion to liquid fuels (or food, etc.,) so the people who grow these crops could be convinced of the benefits in changing what they grow. Bringing this into fruition may be politically challenging, but so are riots caused by people lacking food and transport.

Any noticeable benefits?

The use of biodiesel does not turn buses into quiet zero emission vehicles - indeed very few people would notice any significant difference, apart possibly from the smell, which especially if recycled cooking oil is being used might result in the buses smelling like fast food outlets! However for buses operating on quieter routes and especially in rural areas (where electrification is simply not a viable option) then because it can be sustainably sourced so there is a good case for using biodiesel to fuel buses.

Pure or mixed with regular diesel?

When compared with mineral diesel the use of pure biodiesel to fuel a conventional motor bus engine results in a reduction of some pollutants and an increase in others. Biodiesel fuelled buses are just as noisy with the same levels of vibration as mineral diesel fuelled buses.

Because the carbon in biodiesel emissions is recycled from carbon that was already in the atmosphere [rather than from "new" carbon from oil that was sequestered in the earth's crust] so net emissions of carbon monoxide (CO) and carbon dioxide (CO2) are lower. The emissions particulates are also lower. Biodiesel contains fewer aromatic hydrocarbons (benzofluoranthene & benzopyrenes). However there is an increase in the harmful nitrogen oxide (NOx) emissions.

It is perhaps worth noting that the CO2 emissions from diesels into the streets only affects global climate change - it is not a direct human health issue. However emissions from diesel or other combustion engines into the streets of CO, NOx or particulates are human health issues. So whilst biodiesel may well have a part to play in reducing the use of fossil fuels and therefore reducing CO2 emissions, it is not a solution for reducing the noxious emissions like NOx from diesel bus exhaust pipes.

Biodiesel has a tendency to gel at low temperatures (less than 4° C), it also suffers from issues with micro organism growth and water absorption. Because of the potential severity of these problems biodiesel is usually deployed mixed with regular diesel, perhaps on an 80-90% mineral diesel and 20-10% biodiesel basis. In this format the use of biodiesel has been found to extend the life of various engine components. This is at least partly because of biodiesel's higher lubricity index compared to mineral diesel.

Some forms of biodiesel (eg: ethanol) have a lower 'energy' rating which means that for mile for mile more liquid fuel is consumed than with regular diesel.

Sourcing Problems - Deception!

In late 2007, a bus company which operates local buses in the English town of Reading bought 14 new ethanol fuelled double deck buses to replace the existing fleet of biodiesel powered vehicles. At the time this was the largest order for ethanol fuelled buses in the UK. These buses were introduced into service in May 2008.

However, in October 2009 it was discovered that instead of the ethanol fuel having been sourced from sugar beet grown in the English county of Norfolk (as everyone in Reading had been led to believe) it was actually made from wood pulp imported from Sweden. On learning this Reading Borough councillors launched an investigation into how they, the Reading Transport Board - which runs Reading Buses - and the people of Reading could have been deceived.

In a press release issued by Reading Borough Council on 2009-10-15 it was stated that the use of ethanol would be terminated, although the reasons cited were primarily financial, and not because of the deception. The press release points out that although the current cost of a litre of ethanol is just 2.61% more expensive than biodiesel, the ethanol powered buses are a massive 44.5% less fuel-efficient, making them more than twice as expensive to run than the biodiesel powered buses. The press relase can be read here

(link opens in a new window).

See caption for picture information.
Scania CN27OUD/OmniCity ethanol-fulled bus in
Reading Transport Ltd route 17 livery.
Image & license: Arriva436 / Wikipedia encyclopædia. CC BY-SA 3.0

The case for NOT using alternative fuels

Often touted as cleaner fossil fuels are liquefied petroleum gas (LPG) and compressed natural gas (CNG). However these fuels also have both financial and environmental drawbacks -

Liquefied Petroleum Gas.

  • LPG is a low pressure mixture of propane and butane, which on the bus is stored at pressures between 4 and 7 bar.
  • LPG does not contain any lead, sulphur or benzene.
  • Overall it contributes 10% less to global warming than petrol - and 3.4% more than diesel.
  • Compared with diesel buses, LPG buses emit 5 times as much carbon monoxide and consume 75% more fuel - making favourable tax regimes a necessity for bus operators to use this fuel.
  • In the event of an accident where the LPG escapes into the atmosphere it would be much more dangerous than either natural gas or hydrogen in that being heavier than air it would behave like a liquid fuel (ie: petrol and diesel) and spread along the ground, which is where most people and buildings are usually to be found.
  • As with petrol (but not diesel) LPG is highly flammable.

Compressed Natural Gas.

  • Compressed natural gas is stored on buses at high pressures of up to 200 bar.
  • CNG spark ignition engines are much less fuel efficient than compression ignition diesel engines - consuming 20% more fuel than low sulphur diesel buses.
  • CNG bus exhaust may contain less NoX than diesel bus exhaust but it also contains more carbon-dioxide (CO2) than from diesel fuelled buses.
  • In addition CNG buses also emit methane, which has a greenhouse gas value 21 times greater than CO2 - in effect this means that they actually increase greenhouse gas production by a typical 19% (compared to a low sulphur diesel bus).
  • It has been reported that although the mass of particulates emitted by CNG may be lower than diesel, the particles are finer - so travel more deeply into our lungs.
  • Both CNG and diesel require exhaust after treatment to try to limit noxious emissions.
  • Compared with diesel buses, CNG buses are heavier, carry fewer passengers, have problems with range, are less reliable, more expensive to maintain and the cost of the re-fuelling facilities is horrendous. Transport operators who use them report that the overall lifetime costs of CNG tend towards being double those of diesel.

So, not only have bus operators who use them found them to be financially less viable than diesel buses but despite all the politically-correct hype their use means that the global environment suffers a significantly worse 'hit' than it currently receives from diesel buses.

In 1990 the Canadian city of Toronto introduced a fleet of CNG s replacements for both electric trolley and other buses. At the time they were hailed as being no-pollution replacements (sic) for trolleybuses, however within five years CNG operation had been withdrawn from the city. Whilst 50 buses were converted to diesel, 75 had very abbreviated lives and went straight to the scrap pile. It seems that few people want to talk about what has become seen to have been a disastrous money-wasting fiasco.

When a Swiss city introduced CNG buses to its fleet it also had to spend SFr400,000 (Swiss Francs) on the bus garage, including installing a gas detection system, creating an anti-explosion zone, modifying the ventilation system and improving both the fire detection and alarm systems. In addition SFr1 million was spent installing gas distribution, compression and storage facilities.

See caption for picture information. See caption for picture information.
CNG bus on London's high profile Millennium Dome route M1 in 2000. Some people see buses which use CNG or LPG as being clean air options - even though these are still finite fossil fuels and have some environmental drawbacks more severe than diesel. Having experimented with fuel cells and found the technology to not be mature enough for serious use, in 2008 the Canadian city of Vancouver replaced its life-expired trolleybuses with a fleet of 230 new trolleybuses. This image shows the first of the fleet and is sourced from the "yahoogroups" electric trolleybus discussion group.

Hydrogen Buses

In December 2003 London received three experimental Hydrogen powered "fuel cell" buses. This was as part of a global series of trials being carried out under the European Union’s CUTE (Cleaner Urban Transport for Europe) project. In all 9 EU cities were involved plus Reykjavik (Iceland), Perth (Australia) and Beijing (China). The reasoning behind the ‘CUTE’ program was to test the buses to see how they coped in different traffic and climatic conditions - which implied rigorous usage to test endurance, reliability, to look for weaknesses, etc. London was a key city in these trials because of its extreme stop-start traffic conditions where travelling for much more than a minute without stopping is fairly unusual. The trials in these 11 cities were part of a long-term development programme which previously saw the testing of one fuel cell bus in the Canadian city of Vancouver.

In theory fuel cell technology sounds wonderful. The hydrogen "fuel" stored on the bus is converted into electricity, with the only waste product being water vapour (ie: steam!). This means that these are electrically driven buses - and there is no pollution at point of use.

For some reason these were not promoted as hybrid buses; possibly because the idea was not to detract from the use of hydrogen and that in that era the use of hybrid buses was little known.


Fuel cell technology is still very much experimental and is so energy inefficient that whilst using these buses would have resulted in a reduction in air pollution in the areas they served, (ie: their 'local environment') producing their hydrogen fuel would have still negatively impacted upon the global environment. According to information obtained from oil company BP, when renewably sourced electricity is used to produce the hydrogen emissions of the harmful greenhouse gas CO2 increase by 582 tonnes for every Gwh of power generated. Furthermore, for every 9Gwh of energy invested just 1Gwh of usable power will reach the buses wheel - generating, compressing & storing the hydrogen will waste the rest of the energy. As a contrast trolleybuses are a tried, tested and proven technology successfully used in over 350 towns & cities globally. They are also very fuel efficient - when sourced renewably over 90% of the electricity actually gets usefully through to drive the vehicle. When trialled in Vancouver, Canada they found that one fuel cell bus consumed as much power as a dozen trolleybuses and unlike trolleybuses which can work 24+ hour duties without even needing to be refuelled (OK, so occasionally they do change the bus drivers!) the fuel cell buses needed refuelling after just 4.5 hours - barely half a workday! So for this plus other reasons resulting from their comparative trials they are replaced their old trolleybuses with a fleet of 230 brand new low-floor trolleybuses.

Another issue for these fuel cell buses was that they were so heavy that their unladen weight was roughly similar to that of a diesel bus carrying a full complement of passengers. Since governments usually set legal limits on how much a bus may weigh (partly to reduce wear & tear on the road surfaces) the net result was that their passenger capacities were lower than fossil fuel or trolleybuses of comparable size.

As with CNG buses, hydrogen buses must be equipped with leak detectors - because hydrogen is extremely volatile.

Considerably more information on fuel cell buses can be found here (link opens in a new window)

As an aside, the CUTE trial was extended for an additional 13 months from the initial completion date of December 2005, and finished on 12 January 2007. Because of their unique nature once the London hydrogen fuel cell buses were withdrawn from service they were donated to museums, albeit without their hydrogen equipment - which was reclaimed by the manufacturers for further development works. They have gone to the London Transport Museum, The Science Museum and the Beith Collection in Ayrshire, Scotland. Being modern buses which in no way could be considered to be ‘life - expired‘ it is unfortunate that further use could not have been found for them, perhaps as battery electric or trolleybuses at one of the living museums.

See caption for picture information. See caption for picture information.
One of London's first batch of fuel cell buses, outside Stratford station. Having arrived at the docks the first of Perth, Western Australia's fuel cell buses is unloaded from the ship. Note the pure water vapour (steam) rising from its exhaust pipe.
Image: Promotional material issued by the Government of Western Australia Department for Planning and Infrastructure.

Fuel cell Hybrid buses

As part of the HyFLEET:CUTE project June 2009 saw a German bus company unveiling the first of an experimental fleet of fuel cell hybrid buses which use lithium-ion battery packs. They are being seen as successors to the CUTE buses described above and the idea is that a small fleet will be supplied to several towns and cities to evaluate the technology. As with the CUTE buses the 'greeness' of these vehicles largely depends on how their hydrogen fuel is sourced - typically (at present) it comes from fossil fuels and requires so much fuel to be used that when comparing the total energy input these vehicles consume even more energy / result in more air pollution than ordinary diesel buses.

Because London's decision makers were more interested in possible future solutions for 20+ year‘s time and not seriously working to reduce air pollution ‘right now‘ further trials were proposed, this time using ten hydrogen powered buses, of which five would be hydrogen fuel cell buses and five would be hydrogen powered internal combustion engine (ICE) motor buses. In addition the plans included some other types of fuel cell vehicles (such as dustcarts and taxis) and London's senior transport managers issued a stern rebuke to the various fuel cell bus manufacturers for making them so expensive(!)

All this was proposed under the auspices of TfL and the London Hydrogen Partnership's 'London Hydrogen Transport Programme'. Since TfL had allowed the hydrogen fuelling facility used by the previous fuel cell buses to be decommissioned so the plans had to include building a replacement.

In August 2008 a different Mayor (Mr Boris Johnston) who won the Mayoral election earlier in the year decided that as part of a policy of reducing expenditure and not increasing the local taxation levied on the people of London he would scale back his predecessor's plans and deleted the ICE buses. Later he was able to secure EU funding to add an extra 3 fuel cell buses to the scheme, so that the entire fleet was now expected to number eight of these buses.

The first of this next tranche of fuel cell buses was expected to enter service in December 2010 but because of snowy weather this was delayed until late January 2011. The buses were built by Wrightbus of N. Ireland using a specially modified version of its Pulsar 2 body structure on the VDL SB200 chassis. They feature ISE hybrid-electric drive and Ballard fuel cell technologies. To help reduce overall energy consumption they regenerate their braking energy using ultracapacitors. 12m [40 ft] in length they are 11' 2" [3.4m] high, they seat 34 passengers, have space for one wheelchair and weigh 11,597kg [25567 lbs].

Funding for this hydrogen bus experiment jointly came from Transport for London (TfL), the Department of Energy and Climate Change (DECC) and the European Union via the Clean Hydrogen in Cities (CHIC) project.

click me for video A video of this fuel cell bus has been placed on the 'youtube' film sharing site and can be watched (in new windows) by clicking either the projector icon or the link below. It is very much suggested that you turn on your sound, so as to fully appreciate the very different sounds of this bus. http://www.youtube.com/watch?v=Mm7o61OQg2w

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The first of London's next batch of hydrogen buses, seen on the bus stand outside Tower Gateway Docklands Light Railway station.
The elevated view neatly shows that when first delivered the buses sported six roof mounted hydrogen fuel tanks, however since subsequent experience proved that just four tanks were required for the leisurely 18 hour duty cycle these buses perform, so two have been removed.
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Inside the bus, showing the distinctive red seating fabric which has the words 'Hydrogen Bus' in white emblazoned on the seat back. The rear of the bus, showing the H2 hazard warning logo.

2012 Olympic / Paralympic No-Go!

Because the new hydrogen fuelling facility was located very close to the site of the London 2012 Olympic and Paralympic Games it was decided that for security reasons the use of this facility (and by extension, the Hydrogen buses) should be stopped from July to September whilst the Games were underway. A side effect of this was that delivery of the last three buses was delayed until after the games had been completed.

Diesel / Fossil Fuel Hybrid buses...
are these even a partial solution - or just 'cloak and mirrors'?

Some cities have been looking at what are known as hybrid buses as ways to reduce air pollution, improve the attractiveness of their bus services and operate (partially) electric full-size buses without overhead wires.

Trials conducted with these buses between 2004 and 2006 have shown that as a general theme they are less polluting and use less fossil fuel than regular (diesel) mechanical buses, and based on this their advocates are trying to hoodwink the public into believing that use them would represent both the best / most advanced way forward which present day technology (in the public domain) can offer - as well as being 'the' solution to bus sourced air pollution.

It cannot be reiterated enough that fossil fuel powered (diesel, etc.,) hybrid buses are NOT 'ZEVs' (zero emission vehicles) and that as with ordinary 'mechanical transmission' buses they still pollute their local environments - ie: the streets we use / the air we breathe.

The only buses capable of being true 'ZEVs' are those which are directly connected to the grid power supply system (trolleybuses / roadway powered) and those travel 100% of the time using electric energy stored in batteries / capacitors, with that energy having been received without the use of an onboard fossil fuel engine. These - along with electric trams, streetcars & light rail - do not give off any tailpipe pollution at all!

Because this is a complex topic which also creates a diversion away from the central theme of this page so hybrid buses are more fully explored on their own dedicated page.

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Direct links to other Buses pages...

Easy access for all! About Railways Transport Integration - making it all mesh together as one seamless entity. Its high time we stopped polluting our cities - we have the technology, but not the willpower
The importance of well designed, functional stops and stations.
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A look at bus transport. Roads
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Road pricing, road-user charging, motorway / expressway tolling, cordon charging and urban 'congestion' charging.
Bus priority systems
Feeders for mainstream transports and specialist transports meeting different needs.
About light rail - modern trams and streetcars.
The importance of freight trains.
Specific examples of how tram stops fit in the street scene and that trams and parked vehicles can coexist!
The bus gets a stylish makeover.
Railway electrification. Ideas to make roads safer.
Often overlooked alternative transports
Traffic free pedestrian zones and transit malls.
Does speed kill - or is it only inappropriate speed that kills (too fast / slow)?
Different types of passenger train as defined by the type of service they provide.
Create urban green corridors.
re-load this page. Vehicles need to go somewhere at journey's end.
Let traffic congestion make you the unwilling victim of the crime of time theft!
Where different types of guided transport operate over shared infrastructure.

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