Monorails, Maglevs and 'Cabin' Transports.

Monorails are often thought of as futuristic "space age" transports, yet instead of seriously proposing their introduction into the modern "real world" cityscape transport planners seem to have condemned them to just 'fun' locations - such as the 1990 Gateshead Garden Festival, England. There could be several reasons for this, including...

• They are perceived to be a 'low-capacity' transport,
• They are not thought as being capable of providing a viable urban public transport,
• The public like the views of the passing cityscape but in their ignorance consider things they like as just being for when they are on holiday,
• Visual intrusion (as seen from street level).

The view inside one of Sydney's low capacity vehicles (below left) should explain why some people think of monorails as being for 'low capacity' routes only, however the contrasting view inside the high-capacity Seattle vehicle (below right) shows that with appropriate vehicle designs monorails can provide a viable alternative to other transport technologies.

Seattle's "Alweg" trains are 122' (37.2 m) long, 10'3" (3.1 m) wide, and 14' (4.27m) high. Each train can seat 124 passengers and can carry 326 standing passengers for a total of 450 passengers.

Seattle's monorail opened in 1962 and has been very successful - both financially and in the popularity stakes. Despite their age the "Alweg" trains it uses still look futuristic. They are in fact not tied to any proprietary manufacturer and therefore whilst currently none are being built anywhere there would be no copyright issues if a transit manufacturer (or any other enterprising company) wanted to build more. OK, so the electrics and some other technical specifications would be of a more modern design, but the basic vehicle design could be copied and still remain forward looking.

Unfortunately this is more than can be said about some of the vehicle designs offered by present-day manufacturers, which, with the walk-through interior replaced with smaller, compartmentalised, segmented interiors actually represent a retrograde step in monorail train internal design.

Visual intrusion is a subjective issue - certainly for new developments where the transport can be incorporated as an integral part of the buildings (as seen below - left) there should be no problem, although their installation in older, historic, areas could meet with some perhaps justified resistance.

There is more about visual intrusion (including a comparison with a British example) in the section which looks at hanging monorails below.

One country which really has taken to monorails is Japan. Unlike most urban railway systems in Britain / Europe / The Americas and Australasia most of these Japanese monorails are profitable in operation - which means that they need neither subsidy nor fares revenue support!

The images seen so far all depict 'straddle' type monorails. They are called this because the vehicles sit upon (ie: straddle) the track.

Another type of monorail is the 'hanging' monorail. As the name suggests they are called this because the vehicles 'hang' below the rail. Both Japanese hanging monorails seen below use the Safege system which originated in France.

At 15.5km in length the Chiba City "Townliner" Urban Monorail is the longest hanging monorail system anywhere globally. It is also the only dual-beamed (monorail equivalent of 'twin-track') Safege-type system. Long term plans are for this monorail to be over 40km in length. At present it features two lines and 18 stations. It opened in 1988.

A hanging monorail was chosen for this location because the area occasionally suffers wintry weather - so with the running surfaces and train bogies inside the beams this type of monorail enjoys greater protection from the elements.

Another Japanese hanging monorail is the 6.7km Shonan Enoshima Line which links Ofuna railway station to the coastal area of Enoshima (20 miles southwest of Tokyo). Opening in 1970 this was the first fully commercial monorail based on the French-developed Safege system.

This line is predominately single-track, with passing loops at stations. It features sharp grades (up to 10%) and several tunnels.

Europe's most successful hanging monorail is the German Wuppertal Schwebebahn.

Wuppertal's monorail first opened in 1901, and for most of its 11km route is located above the river Wüpper, however at the western end it runs above a main road where by not requiring any roadspace it very effectively avoids traffic congestion. Admittedly the system is not the prettiest to look at and is a little noisy but the superstructure is from a different era when people just marvelled at the technology.

This system was built by the same person (Eugen Langen) who had previously built the Schwebebahn in Dresden (also Germany). The Dresden Schwebebahn is a short distance suspended funicular railway, it is looked at in greater detail on the Niche Transports page.

A more modern German hanging monorail is the H-Bahn. Located at Dortmund University this demonstration line provides low capacity but very frequent transport between several campuses, the science park, the local S-Bahn railway station and the suburb of Eichlinghofen.

The first section of the H-Bahn opened on 2nd May 1984 since when it has been extended several times so that nowadays the total length of the system is about 3km with the most recent extension being a 1.2km route from the S-Bahn station to the science park.

Despite being single track there are two independent interleaved services on the H-Bahn with frequencies of every 5 minutes between Campus North and Campus South stations plus a 10 minute interval service between the science park to Eichlinghofen via the S-Bahn station.

The H-Bahn is fully integrated into the public transport networks of the city of Dortmund and the regional fares tariff system, so that passengers in possession of a ticket valid for the local trains / trams / buses can travel on the H-Bahn at no extra cost.

Unlike the Wuppertal installation this system is whisper quiet and features fully automatic driverless operation. For safety (especially at the elevated stations) the H-Bahn stations feature platform doors which open slightly in advance of the trains' doors.

The vehicles have a maximum speed of 50 km/h (31mph), a maximum elevation of 16 metres above ground and seat 22 passengers with space for a further 20 standing. Average daily ridership exceeds 5,000.

Small vehicles such as these are often called Cabin transports. Their function is to provide low capacity transports at locations where passengers need frequent services (typically every 2 - 10 minutes). They usually feature fully-automated 'driverless' operation which also makes them what are known as automated guided transits and / or people-movers.

Varying the service frequency is just one way of tailoring overall capacity to demand. Another option is to adjust the train lengths - usually cabin transports will feature trains of between one and three 'cabins' at a time. Whilst longer trains are technically possible it would often be more economic to use fewer but longer vehicles

The most typical locations for cabin transports are airports where they ferry passengers and staff between the various termini and indeed the first full commercial H-Bahn installation is located at the nearby Düsseldorf airport, where it is known as the Sky-Train.

The Düsseldorf airport "Sky-Train".

The Düsseldorf airport "Sky-Train" is about 2.5km in length and features four stations which link the nearby mainline railway station (which is served by local and InterCity trains) and the off-site car park with the main airport terminal building. Travelling between airport and main railway station takes about 5 minutes. Passengers coming from Düsseldorf and Solingen can also take a local train which uses the airports' suburban railway station, this being located next to the airport hotel and just a few minutes walk from the terminal building.

The introduction of the Sky-Train is reported to have resulted in a significant drop in road traffic levels around the airport. Furthermore by linking the airport to an existing mainline railway (without having to divert the trains along a new alignment) the airport's catchment area has been significantly increased. This also helps reduce air congestion (in the skies) as passengers on shorter journeys can take the high speed 175mph ICE (InterCity Express) train instead of short-haul connecting flights. It is a shame that a similar philosophy could not be followed for other airports, such as London's Heathrow and Luton airports which are both very close to mainline railways too.

Some hanging or suspended Cabin transports use small gondola type vehicles or even open chairs. Typically these will be used at leisure-orientated locations, rather than as part of an urban transport system. Notable exceptions include New York and Singapore where the hanging transports link the main cities with nearby small islands.

Sometimes the smaller cabins will carry (seat) so few passengers that they will be thought of as being "Personal Rapid Transports" (or "Transits" in the American dialect), which is often just referred to as PRT. However it is not possible for any of these suspended 'mini' cabin transports to be true PRT's - this is because the principle behind PRT is that once aboard the passengers tell the vehicle where they wish to go and it will take them there, travelling via the best route, whilst these systems only serve fixed routes over which the passenger (usually) has no control.

The Japanese Skyrail gondola transport is new variant of hanging gondola. It is a fusion between a hanging monorail, an aerial cable car, and a people-mover. It features driverless gondola-sized carriages which are designed to carry either 25 or 37 passengers (depending on information source), travel at up to 18 km/h and are suspended from a single concrete track. Between stations traction comes via an attached cable whilst in the stations the carriages release the cable and (for acceleration and braking) use linear motors.

With this system the carriages can climb steep slopes like cable suspended gondola systems and follow curves like normal monorails.

Officially known as the Hiroshima Short Distance Transit Seno Line this line is just 1.3km in length it features three stations. It was built to connect a housing development with Midoriguchi station of the JR-West San-yô railway. Originally listed as a Japanese AGT (automated guided transport / transit) it has since been reclassified as a monorail. Different sources suggest that it was opened either on 28th August 1998 or the same date in 1999.

A more well known (in Asia) version of this is the Slope Car, which is installed in over 80 locations in Japan and South Korea.

The principle behind Slope Cars is the fusing of monorail and funicular technologies to provide localised and often 'on demand' transports where there are steep slopes or stairways, for instance between entrance gates and buildings. Often they will also be installed to provide 'special needs' access, however as they are normally fairly slow moving so people who can walk may still prefer to do so. Sometimes however they may be used at locations where there is no foot access, so obviously this precludes the walking alternative. Most slope cars com in the form of straddle-beam monorails, but there are also suspended monorail variants too. Unlike normal monorails which generally use rubber tyres running on a concrete track, slope cars use a variant of steel rack rail and pinions. This is what gives them a much greater hill climbing ability.

Slope car systems will typically operate like lifts (elevators) and provide an on-demand service where to start the journey a user pushes a button, and it automatically stops at the destination. The smaller sized vehicles will carry just a few people, but as explained elsewhere on this page they will not be PRT's, because they still only follow a fixed route over which the passenger has no control. Transports for hilly locations are looked at in greater detail on the Niche Transports page.

Perhaps one of the most extensive airport Cabin transport systems to have been built is the original 'people-mover' at Dallas Fort Worth (DFW) airport in the USA. Whereas most airport people-movers usually just shuttle to and fro between two stations (and possibly calling at an intermediate station or two) this one was different as it was 15 miles (24km) in length and featured over 30 stations. So it was more like a transit system for a small town(!) providing a variety of services serving different stations and featuring one, two and three car formations.

However, even this was not a PRT, as despite the extensive nature of the system the trains still followed pre-set routes and called at specified groups of stations; plus, the trains were for people who were not always travelling between exactly the same start and end points.

The DFW Airtran APM airport people-mover.

A video of the DFW Airtrans APM has been placed on the 'youtube' file-sharing website the link below - link opens in a new window.
http://www.youtube.com/watch?v=rh53ke7bIjw

Additional information: Known as the Airtrans APM it opened in 1974. Services provided varied but at the height of operations it was providing three sets of services for passengers, airport staff and a special service for American Airlines. The fleet consisted of 68 cabin-sized vehicles which seated 16 passengers and offered standing room for a further 24 passengers. The system had an overall capacity rated at 9,000 people/hr. The top speed was just 17mph (27km/h). Although there were some initial teething problems it eventually became very reliable. During its 31 years of operation there were many technical upgrades, some of which took advantage of advancing technology, eg: circuit boards were replaced with microchips and the original eight-track cartridge system which was used for the passenger announcements was later updated to a compact cassette system and still later to a digital voice synthesizer.

Although very successful it suffered from a few shortcomings and these, combined with changes in how the airport operated (the rise of the 'spoke and hub' system meant that an increasing number of passengers changed flights here) caused its eventual demise. Its closure was partly because services operated as a one-way loop which coupled with the somewhat sedate top speed meant that some journeys took much longer in one direction than the other direction (possibly as much as 30+ minutes), resulting in transfer times being too long for passengers on multi-stage journeys where they also needed to change terminals when changing flights here. In 2003 the airport staff and 'non-secure' passenger services were replaced by contracted-out motor bus services - airports were never known for their environmental credentials so its very unlikely that anyone even considered the extra air pollution from the motor bus exhaust fumes. The APM closed in 2005, replaced by an airside (ie: 'secure') people-mover dedicated to speeding passengers between terminals known as the 'Skylink' and which (like the former APM) is electrically operated.

Despite not serving the car parks, hotels, etc., Skylink is still the largest airport people-mover system anywhere globally. Its 64-vehicle fleet serves 10 stations on 5 miles (8km) of two-way elevated guideways. Services run every two minutes and travel at speeds up to 37mph (60km/h) with an average passenger ride time of just 5 to 8 minutes and a complete circuit taking about 18 minutes.

Several British airports also use automated people-movers, including Stansted and Gatwick; at one time the latter even had two of these systems. The installation which is still open links the two passenger terminals and usually uses triple unit trains although sometimes shorter trains are operated. The other installation used to link one of the terminals with a 'satellite' terminal - it used single unit trains. Closure came with the rebuilding and significant expansion of the terminal.

Both Gatwick and Stansted use an Adtranz (formerly Westinghouse) system which features rubber-tyred vehicles that are guided by means of a central rail. Dating from the 1960's, for many years this system was the most successful people-mover technology globally. Primarily it was installed at airports but in Singapore there is also a 7.8km 'line haul' installation which acts as a feeder to the Mass Transit Railway (urban / suburban rail system which links many areas of Singapore Island with Singapore City). One unusual feature of this line is that where it passes close to a residential area the window glass automatically becomes opaque. This is achieved using similar technology to LCD display systems and is done to preserve the privacy of local residents.

Singapore actually has three such automatic guided transport systems, all of which serve new high rise housing estates and act as localised feeder systems for the MRT (Mass Rapid Transit) network. The systems are still being developed, so that some stations (and sections of line) will remain unopened until the residential developments they have been built to serve are populated.

Fully automated rubber tyred airport style people-mover systems were chosen because it was felt that despite the higher initial installation costs fixed infrastructure transports would be more beneficial than motor bus based systems. There are various reasons for this, including that (unlike road-based motor buses) these transports...

• will be immune to delays from road based traffic congestion and traffic signals,
• that they will not themselves add to the total amount of road traffic;
• being electrically powered they are cleaner, thereby helping reduce the total amount of air pollution.

• it will be easier for them to keep to the published timetable and (where appropriate) make connections,
• they help to save land space which in Singapore is at a premium,

In Singapore these are known as LRT lines (light rail transport / transit).

Only the Bukit Panjang LRT line uses the Westinghouse system, although at one time it was also used on the Singapore Changi Airport 'Skytrain' people-mover. The other two lines (Sengkang LRT and Punggol LRT) use a newer Japanese people-mover technology. In addition the people-mover at Changi Airport has been updated with the newer vehicles. This was done as part of a project which included building more terminals at the airport and enlarging the people-mover to serve them.

As the three LRT systems are used as part of urban transport systems passengers must pay fares to travel on them. However there is no charge for travelling on the people-mover at Changi Airport.

Performing a similar function but very different operationally is the funicular style Italian MiniMetro which can be found in the city of Perugia.

Faced with severe environmental issues related to motor vehicle exhaust fumes the Italian city of Perugia decided that the only solution lay in restricting car and motorcoach access to parts of the city centre. However they also recognised that another part of the solution lay in improving public transport so that fewer people would want to drive their own cars and that visitors who come by motorcoach should also be happy to leave their vehicles outside of the city centre. Therefore, in addition to increasing car and coach parking capacity on the outskirts of the historic city centre and installing escalators between the parking areas and the city centre, they built a new metro system.

Being a small city (population a little below 165,000) on a hilly location they reasoned that they needed a lower capacity system capable of climbing steeper gradients, and wanting to maintain attractiveness by means of a high service frequency they opted to use lower capacity 'cabin' type vehicles which would operate as a funicular railway.

Known as the MiniMetro the Perugia system can operate so frequently that waiting time is almost non-existent. 3.2km (2miles) in length the system currently has seven stations, although a second line with two further stations is planned. There are 25 rubber-tyred vehicles which like normal railways can be added or removed from service as required depending on expected passenger numbers. Five metres long each, they are fitted with eight tip-up and one fixed 'special needs' seats and have a maximum capacity of 50 passengers. Other features include an acoustic 'doors closing' alarm and LED display which provides 'next station' and destination updates. The systems' top speed various between 36-43km/h (22-26mph)

Services are only cable operated between stations, as at the stations they are automatically detached from the cable and conveyed through the station by an independent conveyor system.

Although generally welcomed the MiniMetro has attracted some complaints by people who live close to the route who cite the continuous hum of the cable pulleys as being somewhat noisy.

The name MiniMetro is a registered trade mark, so can only be used on systems developed by the Italian company Leitner, who are specialists in automatic aerial ropeways and chairlifts - so it is not surprising that some practices from these transports (such as disengaging from the cable at stations) have been ported over.

Funicular / cable railway system are looked at in greater detail on the Niche Transports page.

In October 2005 it was announced that the British "ULTRA" cabin transport system would be installed to serve the new Terminal Five of London's Heathrow Airport.

The ULTRA system uses very small battery electric powered cabins which have a maximum speed of 25mph (40 km/h).

Ultra is the only true PRT (Personal Rapid Transport / Transit) seen on this page. This is because it operates on the basis that once aboard the passengers tell the vehicle where they wish to go and it will use its special dedicated track to take them there, travelling via the best route. It is this feature which primarily differentiates PRT from normal people-movers and others types of public transport, as the latter only served fixed routes over which the passenger (usually) has no control.

At Heathrow Airport ULTRA will link the various car parks with the terminal, with it providing a more rapid and frequent service than the more traditional services which use normal motor buses. Passengers arriving at the airport car parks will be able to summon an ULTRA cabin from the nearest 'stop' and after a wait which typically will be under a minute will be taken straight to the airport terminal. Passengers flying into the airport will be able to board an ULTRA cabin at the terminal and after telling it the number of the stop which is nearest to their car will again be taken straight there, rather than being required to travel on a bus journey which follows an often circuitous pre-set route. At the time of writing Terminal 5 has justy opened but the ULTRA is still under construction.

One unresolved issue is that ULTRA cabins are designed for just four passengers, but sometimes passengers travel in groups of more than four people (eg: families) and it is not known whether these groups would be required to split up and take a second ULTRA cabin or will be able to just 'cram in' with children sitting on adult's laps. Especially if there is just one adult (or other responsible person) in the group it would be felt undesirable to allow children to travel alone. Likewise, expecting children to travel in another cabin with a complete stranger...

Opening on 16th August 1984 the Birmingham (UK) airport Maglev people-mover was a global innovation by being the first public transport installation (in the present era) to use magnetic levitation. Linking Birmingham International Railway Station with Birmingham International Airport and the National Exhibition Centre (NEC) it used two 'cabin' sized vehicles which featured electromagnets at each corner (to provide the lift) and linear induction motors (for propulsion). The trains "flew" at an altitude of 0.6" (15mm), carried up to 40 passengers (plus luggage) and with a maximum speed of 26mph (42km/h) the approximately 2000' (620 metre) journey lasted for about 90 seconds.

Because the Maglev system always formed part of the airport's essential infrastructure as the link to the railway station no fares were ever charged for its use.

Maglev technology uses powerful electro-magnets so that the transports float along the track on a cushion of air. This reduces friction, gives a very smooth quality of ride and makes such vehicles relatively quiet. Magnetics are also used for propulsion and braking.

The advantage of this technology over conventional steel wheel technologies is that there are massive savings in maintenance and there is the possibility of full 24-hour service - conventional railway tracks must have every stretch inspected every 72 hours (or even more frequently) and as this involves railway staff walking along the tracks it requires the lines to be closed to moving trains. This is usually done at night - and partly explains why conventional railways cannot offer 24 hours / all-night services. Maglev does not have this issue, as the system should only need periodic maintenance shutdowns - although most travellers and safety officials would probably feel happier if (at a minimum) this was done on a weekly basis.

A video of this Maglev in action has been placed on the 'youtube' file-sharing website. This can be reached by clicking the link below
- link opens in a new window. http://www.youtube.com/watch?v=asVQzbOftqE

In addition to meeting a real transport need this 'showpiece' installation was intended as a working demonstration of the new technology of magnetic levitation. However no further systems were built using the same technology and with the Birmingham installation working reasonably well so no need was seen to keep it up to date with newer technologies as they became available. Advocates of magnetic levitation technology suggest that especially the latter was another reason for the system's ultimate demise.

In the end it became a victim of its own success - because it had been so dependable, for so long, that when it finally needed spare parts there was no replacement parts industry. Furthermore its electronics had by then become several generations behind the times (isn't it just amazing that something so technologically advanced as a maglev can become 'old fashioned' so soon!). Closure came on the 19th June 1995.

Some of this information was sourced from a House of Commons Written Answers session, this link should open a copy of Hansard for the relevant date in a new window. http://www.publications.parliament.uk/pa/cm199899/cmhansrd/vo990526/text/90526w08.htm

Instead there is now a people-mover (marketed under the name of "Air-Rail Link ") which uses the Austrian Doppelmayr/Siemens CABLE Liner Shuttle system. This rubber-tyred system features automated cable traction, and apart from here is also used in Las Vegas, USA.

Often thought of as a 'magnetic levitation' transport was the (West) Berlin, Germany, M-Bahn. This system used a linear synchronous motor in the guideway which reacted with permanent magnets on the vehicles to provide 85% of the support as well as propel the trains. The vehicles were also fitted with small lateral and vertical rollers which provided 15% of the support as well as helping keep the vehicle within preset lateral limits.

Very much experimental in nature there were just three stations along a 1.6 km route which took the train very close to the former division between the Eastern and Western sectors of the city.

After Berlin's reunification it was felt desirable to reopen the sections of U-Bahn (underground railway / subway) which had closed because of the city's division and as a result the early 1990's saw it become necessary to close the M-Bahn.

In March 2005 the 9.2km Tobu-Kyuryo Japanese "Linimo" urban maglev monorail carried its first passengers. Unlike previous Japanese applications of maglev technology which had been developed with high-speed long-distance travel in mind, Linimo was intended to develop a variant suitable for urban transport which could provide an alternative to steel wheel and rubber tyred urban railway (metro / subway) systems. In this way Linimo has become both the first application of maglev technology on a monorail and the first commercial automated urban maglev.

The trains are based on the well-tested HSST-100 maglev design. They have a theoretical top speed of 200km/h, although being an urban line with 9 stations in virtually as many kilometres the station spacing is too close to allow such speeds to be reached in practise. On this system the top speed is about 130km/h. Traction comes from linear motors, with the trains floating 8mm above the track when in motion.

As with some of Japan's other urban transports most of the line is elevated, including sometimes directly above city streets, although there is also a tunnel section of about 1km in length. Curiously, services have to be suspended for safety reasons when wind speeds exceed 25 m/s, with (apparently) this being a relatively common occurrence in the area.

Being the first commercial implementation of a new type of transport technology the line has suffered a number of highly publicised technical breakdowns, especially during the 2005 Expo when twice in March 2005 far higher peak hour demand than the line's carrying capacity saw the number of people inside trains exceeding the design capacity of 244 passengers/train with them being unable to levitate. The design capacity of the system with these triple carriage trains is 4000 passengers/direction/hour.

Internally the Linimo trains feature the usual (for Asia) full walk-through facility whilst the fronts are of a novel see-through "gem cut" design which in an emergency will allow evacuation through either end.

Exterior and interior views of the Linimo Maglev Monorail.

Several videos of this maglev can be found on the 'youtube' file-sharing website. These can be reached by clicking these links, from where links to further videos can also be found.
http://www.youtube.com/watch?v=s5RzchADGLc (especially note the trains switching tracks at the end of the film)
http://www.youtube.com/watch?v=uXOVXVFw9qI (all links open in new windows).

Meanwhile, in December 2003 Shanghai, China, become the home of a global innovation with the first commercial high-speed maglev line.

The first commercial application of high-speed maglev is the 30km (18.6 miles) double-track line which connects Shanghai to the new Pudong International Airport. With a peak operating speed of 430 km/h (267mph) and average speed of 250 km/h (150mph), each one-way trip has a duration of just 7 minutes 20 seconds.

Pictures sourced from manufacturer's promotional material. For more information visit their websites at:- http://www.transrapid.de or http://www.transrapid-usa.com.

For information on a proposed application of this technology on the British mainland visit http://www.500kmh.com

Several videos of this maglev can be found on the 'youtube' file-sharing website. These can be reached by clicking these links, from where links to further videos can also be found.
http://www.youtube.com/watch?v=y-54gBLwK3s   http://www.youtube.com/watch?v=Zv63RAOarVs (all links open in new windows).

Street Compatible Cabin Transports

None of the above transports are "street compatible", which means that they would require extensive (and possibly costly) infrastructure to be built before they could be brought into service. This in itself is not a problem because for many locations such transports will be appropriate and by being away from the street scene they will be able to provide timetabled, reliable services which will offer travellers a viable and environmentally sound alternative choice to driving and the all-too-familiar problems caused by traffic congestion / air pollution, etc...

However there will also be some locations where there is a need for very frequent lower capacity transports which are capable of operating both on their own private right of way and in the "street" domain - whether shared with pedestrians, other road traffic, or both.

Traditionally this would have meant using minibuses (although they would only really be suitable for use on paved roads) these being the cheapest and simplest form of public transport. However, experience with bus deregulation here in Britain has shown that whilst buses are easy to bring into service their lack of fixed infrastructure also equates to a possible lack of commitment to providing a long term service - or, in other words buses which are "here today" can just as easily be "gone tomorrow"! And then there is the question of air pollution... although it is true that battery electric buses do exist this is an option few transport operators seem to want to explore. Electric minibuses are looked at on the Electric Buses page.

By far the most popular street compatible form of public transport is the tram (or streetcar) and these exist in "Cabin" size too. However as ultra light rail is a duo-rail technology it is looked at on the Passenger Train Variations - Trams, Streetcars & Light Rail Vehicles and the Light Rail Fits In pages.