Railways.

Electric railways have the potential to be the least environmentally damaging form of traction. Although this depends on how the power is sourced, even the dirtiest emissions are easier to reduce at a few power stations compared to many hundreds of moving trains.

Electrification is also a more efficient way of transmitting power, especially on the busiest and most heavily trafficked routes where any additional capacity (either through longer trains or more frequent services) will require proportionally less additional energy when it comes from a common source rather than on each train. Electric locomotives can deliver as much as 2½ times the tractive power output of an equivalent diesel.

With electric traction it is also possible to further increase efficiency through regenerative braking, which means that a slowing-down train can use its electric motors as generators and recycle energy back into the system for other electric trains to use. Electric traction offers significantly improved performance when ascending gradients, plus the possibility of using regenerative braking to cost efficiently maintain safety whilst descending..

For passengers the advantages of electric traction includes improved overall performance and less vibration which results in faster, more comfortable, smoother and quieter journeys. The improved acceleration also means that extra stations can be served with less time penalty - this is especially beneficial to users of minor stations which might otherwise have a less frequent service. Experience has shown that the very act of investing in railway electrification also gives passengers greater confidence that the line is 'valued' by the railway operators and therefore has a secure future. The sparks effect is a well proven phenomena whereby passenger numbers significantly increases when a line is electrified.

Transport operators usually find that thanks to the fewer moving parts and the 'slide out / slot in' modularity of the traction packages electric trains are simpler and cheaper to maintain. As with trolleybuses the reduced vibration and sheer ruggedness of the electric traction system means that although they are more expensive to initially purchase their operational lives will be far longer than their fossil fuel counterparts, so in the longer term they will be more cost efficient.

Critics of electric traction often allege that when the necessary electricity is sourced 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 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, (75% efficient opposed to 35% efficient) and are so clean that they can even be located within cities.

Of course where the electricity is sourced from renewable sources (eg: hydro, wind, waves, solar, geothermal and tides) it will be 100% non-polluting, it is to be very much regretted that despite the potential benefits (and the globally recognised need for humankind to adopt more environmentally sound policies - anyone remember Rio 1992??) only the first two of these are used to any extent.

People who live near rail lines have found that electric trains are also quieter than diesel trains (both locomotives and multiple-unit passenger carriages) and therefore are better neighbours.

Railway Electrification Types.

Railway electrification will usually take one of two forms - via wires suspended over the tracks or by way of one (or two) extra 'electrified' rail(s) located alongside the tracks. The overhead (catenary) wire system is more usual for long distance lines whilst the electric rail(s) system (which is usually referred to as 3rd [or 4th] rail) is more often used on city-specific urban rail systems (sometimes called metro / subway / rapid transit). But, as ever, there are exceptions.

Because of the physical presence of the overhead wires the overhead wire system is sometimes thought to be somewhat unsightly - although modern installations can be less visually intrusive than older systems - but by keeping the high voltage well away from track level this system is considerably safer in areas where people might have access to the tracks. Typical^* voltages used nowadays include 750v dc (primarily on light rail systems) 1500v dc, 3000v dc, 15,000v ac 16 2/3Hz and 25,000v ac 50Hz (or 60Hz depending on the frequency of the local mains electricity system). There are also a few VHV (very high voltage) heavy freight (mining) railways located in sparsely populated isolated areas in North America and South Africa which are energised at 50,000v 50Hz / 60Hz.

The opening of the Croydon Tramlink system was slightly delayed because of a return current leakage to earth near to the tramstop which serves the mainline railways' East Croydon station. Being a new system this had to be rectified before opening as otherwise if electrolysis had resulted in damage to underground utilities the various utility companies would have been seeking (possibly very expensive) redress from the tramway operators.

The fact that the 3rd rail electric mainline railway might also be leaking current is a different issue - as it was here long before most of the utilities it has what are known as 'grandfather rights'.

The electric rail(s) system is cheaper and easier to install but can pose a safety hazard to people who trespass over the railway as well as track maintenance workers and sometimes animals too (especially small mammals). The 3rd rail variant features one extra rail (for the 'live' current) with the electrical return being via the running rails (the rails the trains' wheels 'run' on / use). The 4th rail system uses two extra rails with there being one each for the live and return. In this way there is a 'closed' circuit from where the electricity is less likely to 'leak' into the surrounding ground - a process which can cause electrolysis, corroding metal structures - such as water pipes, sewers, and whatever else is in the ground - to such an extent that they need (possibly expensive) replacement.

Typically^* the electric rail systems will use voltages between 600v dc and 1,200v dc - higher voltages can become impractical because the electricity would arc from the rail - literally jumping or short circuiting to the ground - and completing the circuit back to the power station without providing any useful benefit. Lower voltages require the electrical feeder or sub-stations to be installed at more frequent intervals along the line in order to feed electricity into the system, increasing the cost of operating the railway.

There are several variants to 3rd rail power systems with power being collected from the 'top', 'side' or 'underside' of the rail. The latter two are safer as it is easier to protect against a person accidentally stepping onto the rail. They are also more beneficial in winter when snow and ice can encrust the rails - with the 'top' system it is too easy for the surface to become so covered that it compromises the ability of train to collect electrical power. Occasionally this can cause trains to become stranded, more often however there is just a lot of noise and spectacular sparking as the high currents 'burn' through the moisture. If this sparking happens whilst a train is stationary (ie: stopped at a red signal or calling at a station) it can result in the 'shoe' that collects the power from the electric rail welding itself to the electric rail!! This has happened on open-air sections of London's Underground - causing delays whilst a welder is summoned to 'free' the train.

This might sound surprising but it can - and sometimes does - happen that a train becomes stalled due to loss of contact with the electrified rail. This mostly happens to single-unit multiple-unit trains and electric locomotives, and would be caused by them travelling slowly over complicated junctions where the gaps in the electrified rails are so long that none of the train's power collection shoes are above (and therefore in contact with) the electrified rails. It is less common when a train / locomotive is travelling at even a modest speed - because usually there will be enough inertia for it to reach the next electrified rail before stalling. It is also less common for this to happen to trains formed of two or more multiple-units - because usually even if one of the units finds itself without power the other unit(s) will still have power and this will be enough to keep the entire train moving.

^*Note that the typical voltages detailed above are just that - ie: only typical voltages. Actual voltages can vary somewhat, for example on 750v dc routes the actual voltages can vary between 500v and 900v (or even 1000v as a 'peak' voltage) whilst on 25,000v ac routes the permanent voltages can vary between 19,000v and 27,500v, with peaks as low as 17,500v and as high as 29,000v.

Combination Systems.

Some systems use third rail for part of the route, and overhead wires for the remainder. These exist sometimes because of the connection of separately-owned railways using the different systems, or because of local regulations.

In New York City some electric trains use third rail to reach Grand Central Terminal on the former New York Central Railroad (now Metro-North Railroad) and switch to or from overhead wires when they travel along the former New York, New Haven and Hartford Railroad (now Amtrak) route to Connecticut. The changeover is made 'on the fly' (ie; whilst moving).

The Blue Line of Boston's MBTA uses third rail electrification on the city centre subterranean part of the line and overhead wires whilst above ground. The changeover is made whilst calling at the station which serves the airport (named 'Airport').

In Oslo, Norway, the T-bane system (urban / underground railway) includes both older urban light railway routes which were built with overhead wires and newer routes that right from the outset used the third rail system. Most overhead wire routes were converted to third rail concurrent with rebuilding as part of the T-bane system, however the Holmenkoll Line is still partially electrified with overhead wires. The changeover is made whilst calling at Frøen station.

More detailed information on railway electrification systems plus a reasonably full list of the different voltages used - and where - can be found on these two pages of the free online 'Wikipedia' encyclopædia. Railway electrification system   List of current systems for electric rail traction (links to an external site which open in new windows).

Electric Trains in the British Isles Today.

Nowadays most mainline overhead electrification in mainland Britain is at 25,000v ac 50 Hz. In the past some routes used other voltages (primarily but not exclusively 1,500v dc and 6,250v ac 25 Hz) but - with one exception - they have either been converted to the standard (for instance: Manchester to Hadfield / Glossop) or the lines closed (for instance: Lancaster to Morecambe / Heysham). Over the course of time some lines have been converted between different voltages several times. Light rail systems tend to use lower voltages (typically 600v dc on older systems & 750v dc on newer systems) as this is safer where on-street operation is involved. In Britain we also used to have many electrically operated industrial lines (located at places such as at coal mines) but they have now all been closed.

The 'Southern' 3rd rail system mostly uses (a nominal) 750v dc, except on lines which at one time were shared with Eurostar trains where the voltage was increased to 850v dc. At first the London Brighton and South Coast Railway electrified its suburban services at 6,700v ac 25 Hz using the overhead wire system but after grouping in 1923 the Southern Railway decided to standardise on the London and South Western Railway's (LSWR) (then) 650v dc 3rd rail system which was also in use elsewhere in south London. It is said that this choice was partly influenced by a greater route mileage having already been electrified using the 3rd rail system. For a while some railway depôts in Southern England were electrified at 750v dc via overhead wires instead of 3rd rails as a safety measure for railway staff.

London's Underground uses the '4th rail' system whereby the electrical return uses a dedicated centre rail, and not the running rails. This is supposed to reduce the chance of 'stray' currents damaging tunnel walls, nearby utilities, etc. Although the underground network is nominally electrified at 630v dc the system actually works so that +420v dc is collected from the outer 'positive' (3rd) rail and -210v dc from the centre 'negative' (4th) rail. Where underground trains operate over electrified mainline railway tracks they collect the full line voltage from the 3rd rail and the 4th rail is electrically bonded to the running rails - which also act as return for the mainline trains. At the boundaries where the trains pass between sections of line electrified on the two systems there are gaps in the electrified 3rd and 4th rails which are of sufficient length to ensure that the trains do not (even briefly) electrically connect the systems together. The mainline railway routes which are shared with underground trains are typically electrified at between 660v and 750v, although when the voltage fluctuations described above are bourne in mind so trains using these routes have been known to receive as much as 900v dc.

Apparently in 1930 the voltage was described as being '550v/600v', but during the 1930's it was raised to approximately 630v. There are now plans (2009) to increase this to 750v dc, especially on the 'subsurface' lines, with this to be done concurrent with the introduction of new trains. Reasons for this power upgrade include that the new trains will need more power to operate all the extra features (such as full air-conditioning and high rates of acceleration) which are not found on the older trains. A related issue however is that because of track sharing between trains from different Underground lines so it may be necessary to modify other trains to make them compatible with the higher voltage. This especially applies to the Piccadily line's trains. The idea has been mooted that over time the whole Undergound system could be upgraded to the higher voltage.

For the record the Clapham Common - (King William Street) \ Moorgate - Euston section of what is now known as the Northern Line was originally electrified at 500v dc using an off-centre third rail but concurrent with the 1923-4 closure for widening of the tunnels to make them suitable for standard sized London 'tube' trains the surviving section of line was also converted to standard 4th rail operation. In addition, from its opening in 1906 until the commencement of services to Watford Junction in 1917 the Bakerloo Line used a reversed power supply system whereby the centre rail was the 'positive' and the outer rail was used for the 'negative'. This was done to counter power supply problems caused by too much current leaking to earth via the cast iron tunnel segments.(NB: " means inches; metric conversions are approximate).

Because of the high cost of maintenance London Underground has stated a desire to switch to an overhead power supply system and in the late 1990's it was believed that the Victoria Line would be converted first, concurrent with the introduction of a new fleet of trains. However since train operations was privatised this idea seems to have been dropped. The Victoria Line would have been one of the easiest to convert as its trains do not share tracks with any other lines - how they would have converted the Piccadilly and Bakerloo lines (smaller profile 'tube' lines which share tracks with full size trains) would have been interesting.

Although at one time the different British railway companies located the electrified rails at different distances from the running rails and different heights from the ground a 'standard' has come about using the Southern Railway / London Underground system whereby the powered rail is 'outside' of the running rails (can be either side, but not usually both sides at the same location) and offset 3" (8cm) higher plus 16" (41cm) sideways as measured from the inside of the nearest running rail. Where used the 4th rail is located centrally between the running rails and 1½" (4cm) above it (nowadays only tracks served by UndergrounD trains need this extra rail). One of the few surviving exceptions to the standard is on the Central Line which when it first opened in 1900 used a 3rd rail (energised at 550v dc) centrally located between the tracks, and due to a restricted loading gauge when (in 1940) it was converted to standard it was found necessary to locate the outer rail an extra 1½" (4cm) higher than normal. This only applies to the earliest sections of the line, between Liverpool Street and White City, and as a result only trains fitted with 'high lift' shoegear can travel over this route.

Apart from the Southern and Underground networks London also has several other 3rd rail systems:-

i) The London & North Western Railway (LNWR) electrified some suburban services serving northern and western suburbs using a 4th rail system similar to that being used on the Underground (which was useful as on some routes mainline and Underground trains shared / still share the same tracks). In the 1970's the surviving electrified LNWR lines were converted to 3rd rail, although the 4th rail was retained where required by London Underground trains. More recently the part of the network which is now known as the 'North London Line' was partially converted to 25,000v ac overhead wire; whilst the controversial closure of the station which served London's Financial District saw services which had linked the Financial District with North London being completely killed off and trains from West London being diverted into East London over tracks which (eventually) became dual-electrified using both 3rd rail (for passenger trains) and overhead wire systems (for freight trains).

ii) London's automated Docklands Light Railway uses a 3rd rail system where power is collected from the underside of the electric rail. This makes it physically incompatible with the other rail systems, however as the DLR was always meant to be a self-contained system this is not an issue. Trains are electrified at the light rail standard of 750v dc.

iii) Until it was shamefully disinvested in (aka: closed) on 30th May 2003 (after 75 years of operation) the 23 miles (37km) long fully automated 'MailRail' (Post Office Railway) featured narrow gauge (2ft - approx 60cms) trains which collected 440v dc from a rail mounted between the running rails. (In the stations the voltage was reduced to 150v dc). This line was for letters and parcels only - not passengers - and many people are most displeased with its closure because it ran right through the centre of London, serving nine 'mail' stations (major post offices / sorting offices) including two mainline passenger railway stations, and saved many hundreds of road traffic journeys daily (& much air pollution).

Away from London four other cities use / did use electric rail systems; all of these featuring the 'top' contact system as on the 'Southern Electric':-

i)       Glasgow.
Referred to locally as a 'Subway' (and not the more usual British term of 'underground') this system features 4ft (approx. 1.22m) gauge trains which are powered at 600v dc via an outside third rail.

ii)       Liverpool (Merseyside).
At one time the city of Liverpool was served by three independent railway companies which operated electric trains. Although they all used electrified rails (mostly energised at 650v dc) the systems were incompatible because the power rails were in different positions (relative to the running rails) and one company's services (Mersey Railway) even included a combination of both 3rd rail and 4th rail systems. Changeover was effected by guard manually switching the electrical return to suit the section of line about to be served. (ie: via the wheels or via the 4th rail).

In 1955 the 4th rail section of the former Mersey system was converted to 3rd rail only operation whilst in the 1970's the construction of the Loop & Link tunnels under Liverpool city centre which for the first time physically linked the two mainline systems saw the former Lancashire & Yorkshire Railway's (L&Y Rly) 3rd rail being relocated to what has become the 'standard' position for Britain. To facilitate this the trains were fitted with temporary 'two shoe' power collection equipment which facilitated collecting traction current from live rails in both the new and old positions.

Liverpools' former overhead railway also used 3rd rail traction (at 500/525v dc) and hosted Britains' first dual voltage electric trains which operated over two different railway companies' tracks. To achieve this the L&Y Rly built special trains whilst the Liverpool Overhead Railway (LOR) relocated its 3rd rail from between the tracks to match the mainline railway's position outside the tracks. On special occasions services of LOR trains were also extended over the L&Y Rly tracks (eg: to the 'Aintree' horse racing circuit). The LOR was not nationalised in 1948 and its closure in 1956 saw it earning the dubious distinction of being the only urban mass-transit rail line in Europe to have completely ceased operations. (OK so Britain is 'offshore Europe') Closure came primarily because the elevated superstructure (for which the railway had gained the nickname dockers' umbrella) was rusting and the cost of repairs were beyond the railway's reach, and despite much public dismay & appeals for help it proved impossible to find sources of finance which were prepared to make enough of a contribution towards the costs.

iii)      Newcastle-Upon-Tyne.
The Tyneside area used to have an extensive 600v dc 3rd rail system which was operated by one railway company (North Eastern Railway) so it avoided the incompatibilities which beset Liverpool's network. For safety reasons there was also a small amount of overhead wire electrification in a partially pedestrianised docks area where freight trains used paved tracks. Unfortunately in the 1960's changing demographics saw the more lightly used sections of the Tyneside Electrics being closed and the rest of the system de-electrified in favour of diesel trains, with the BR-built trains of 1955 being redeployed in southern England. Since 1981 much of the route has been re-electrified at 1500v dc using overhead wires as the Tyneside Metro. Despite being classified as 'light' rail these metrocars are at the upper end of what constitutes a light rail vehicle. Unlike most trams they were not designed to be 'street compatible', and as with the Docklands Light Railway the type of service they provide is more akin to a 'light metro' than a light railway.

iv)      Manchester.
At first the Holcombe Brook - Bury - Manchester line was (partially) electrified at 3,500v dc using overhead wires but in 1918 this was replaced with the 1200v dc side-contact 3rd rail system. More recently the surviving section of this route has become part of the 750v dc overhead wire Metrolink light rail system.

For reasons of safety it is very unlikely that any new railway electrification schemes here in Britain would be allowed to use the electric rail system - although extensions to the existing systems are allowed. Instead new schemes would be energised via overhead wires.

Missed Opportunity -- Yet Again!

In 1981 British Rail and the Department of Transport produced a report (Review of Mainline Electrification) which concluded that even on purely commercial grounds not only was 'a substantial programme of railway electrification financially worthwhile' but that the more extensive and faster options would be better propositions than the more modest ones. It also suggested that the most cost effective way to electrify railways would be by a rolling programme whereby a specialised team of experts will electrify a whole series of lines sequentially (ie: when one line is completed they move to the next) as it would optimise resources and expertise, plus give industry the steady long term order book that creates economic stability.

What this report suggested has often been dubbed the network effect - ie: the more lines electrified the more it would be financially advantageous to electrify even more lines! This is because it would enable more trains to run through services without needing a change of motive power en route, and help avoid (as has happened instead - see below) the wasteful situation arising whereby diesel trains travel significant distances over electrified railways because small sections of the journey involves using non-electrified lines.

However despite the manifold potential benefits to British industry and the wider economy the government refused to allow the creation of such a long term investment plan to which it would have to keep, and instead retained what many people see as a myopic policy of judging every line in complete isolation.

Since Privatisation - Stagnation!

In the mid 1990's the government split the railways up into a myriad of small 'bite sized' chunks which it privatised. The company that now runs the railway infrastructure does not benefit from investing in railway electrification whilst the train operating companies have such short franchises that there is no benefit to them in making this kind of investment as they could spend the money and then loose the franchise - effectively losing the investment they made. In addition, with each TOC more or less solely interested in what is best for it and not the wider railway system / environment etc., so some of them have even been replacing electric trains (both locomotive-hauled and multiple-unit) with diesel multiple-unit trains. There have been several reasons fo this, which include

• it has then meant that they can introduce new through services beyond the current extent of electric power supply systems.
• because most of their 'territory' is not wired and it is cheaper (for them) to have one fleet that can 'go anywhere' than two fleets, one of which is restricted in lines it can serve.

As a result more than a dozen years since railway privatisation has passed with there being virtually no railway electrification, except the occasional fill-in scheme to provide diversionary routes for existing electrified lines during upgrading works. The last real electrification scheme which saw diesel trains being replaced by electrics was in Yorkshire and was began by the former British Railways - and even here because of funding problems resulting from railway privatisation it opened with 30 year-old cast-off electric trains from London. Eventually though they were replaced by a fleet of brand new class 333 electric multiple units and since then passenger numbers have been growing at up to 19% per year. Indeed since they began (in 1995) the electric services have been so successful that the trains now carry as much as 75% of some commuter flows (ie: just 25% of passengers from some areas now travel by road) and despite having been lengthened from three to four carriages in length at busy times severe overcrowding can be a problem.

In many ways this passenger growth is typical of what happens with railway electrification - even here in Britain previous railway electrification schemes have proven the sparks effect to be a phenomena which does boost passenger numbers.

Since Privatisation - Possible Retrenchment?

Instead of electrification things here started going in reverse with some so-called 'experts' suggesting that some routes should actually be de-electrified, and although this has not come to pass there have been many instances of new diesel trains replacing electrics, as stated three paragraphs above (click link to go backwards)

Infill electrification or diesel-electric 'twin-system' trains?

There has been much discussion in government and railway industry circles as to whether it is better to 'infill' electrify sections of line between already existing electrified routes so that electric trains can be extended over more routes or to operate 'twin system' trains which can draw power from overhead wires / electrified rails where available and use onboard liquid fuel (usually diesel) generators to power the train's electric drive system when travelling over non-electrified routes. This discussion was at least in part as a result of the Department for Transport starting a consultation process to decide the best way forward for the next generation of InterCity trains to replace both the diesel High Speed Trains (HST) that date back to the 1970's and the electric InterCity225 trains which date from 1989-91.

Some trains, such as the HST and the more modern '(Super)Voyager / Meridian / Pioneer'^(§) trains already operate on the diesel-electric principle whereby onboard diesel engines power generators that power the train's electric drive system. Many people see it as being both wasteful of precious fossil fuels and unnecessarily polluting when such trains travel over railway routes which have benefitted from the installation of an electric power supply system but instead of taking advantage of this continue to use their diesel engines to power the train. ^(§)(Super)Voyager / Meridian / Pioneer trains are essentially very similar trains from the same train builder albeit with different brand names and interior furnishings as per the various TOC's which use them.

Infill electrification requires that money be found to invest in physical infrastructure, which the government has not always been keen to do. For the full benefits of the investment to be realised as many as possible of the trains which use the newly electrified sections of track must themselves be switched to electric working, which in addition to (probably) meaning their replacement with brand new trains will be something that may require more electrification of other routes to be fully achieved.

Twin system trains are effectively trains which carry their own power plant and fuel with them but for part of their journey use an external source of energy (ie: overhead wires or electrified rails). The weight of the onboard power equipment can be considerable, reducing overall energy efficiency as well as increasing maintenance costs and 'wear & tear' on the tracks. If these trains also use the high voltage alternating current power supply system then the electric power transformers (which reduce the voltage to a level which the train's control equipment and motors can actually use) also add to the train's overall weight.

Since privatisation passenger trains have usually been funded by the train leasing companies which actually own them and then lease them to the various TOC's. If new trains are required for the electrification so it is possible that additional funding would become available (from Scottish / Welsh devolved or the British national governments) with the TOC's possibly receiving these funds as a contribution towards the inevitably higher leasing costs.

Maybe there is a need for an industry leader who can issue 'guidelines' which will 'frown upon' diesel trains running under the wires (or over third rail electrified routes), and encourage / even insist upon both twin-system trains and electrification of lines (trunk and fill-in) to render diesel operation on electrified routes as being totally unneccessary??