What is... Electrification?

Electric trains are cleaner, quicker, lighter, quieter and cheaper to run. So why is only 40% of the British rail network capable of running electric trains, and the other 60% is still suffering noisy, cramped, sluggish diesel trains?

The simple answer is infrastructure costs. While electric trains are cheaper to run, an electric train must be powered by electricity received through either overhead wires or a third rail. So while the second electric train is cheap to run, all the costs of putting up the overhead wires (or laying down the third rails) and connecting them to the National Grid must be borne before the first electric train can run. Putting up all the wires and transformers for a railway line to take electric trains currently costs about £250,000 per single-track kilometre.

Here's a map showing the parts of the network that are electrified:

British railway network, showing electrification (as at 2012)

First, let's look at the benefits that "electrification" can deliver. With a diesel train, the train must carry around fuel and then generate power by burning that fuel in a diesel engine. But with an electric train, the train can simply tap straight into the electricity, and use that electricity to turn motors. Motors are much lighter than engines, and combined with the savings on having to carry around the fuel, the train is much lighter.

As a result, electric trains can accelerate much faster than diesel trains, making them excellent for suburban routes with lots of stops. What's more, the improved acceleration permits trains to run closer together, meaning more trains can run. Time and again, newly-electrified railways see a significant upturn in usage, often known as the "sparks effect", as improved capacity and speed combine with modern, clean electric trains to yield a much more attractive way of commuting.

The benefits are by no means limited to suburban trains, though: electric trains can pack more power for the same weight, and thus much better performance for longer-distance traffic. It's no coincidence that all the world speed records for trains since the 1970s have been set by electric trains; specifically, by high-speed trains in France and Japan.

Nonetheless, electrifying small, dense, intensively-used suburban networks is usually most cost-effective, since you convert the greatest number of services to electric operation for the least total cost outlay. And thus goes the history of British railway electrification: first to be electrified, in the early 20th century, were suburban lines in Liverpool, Newcastle and south London - all using different (and incompatible) electric voltages and transmission systems. (Indeed, none of them still use the system they first pioneered!)

After the railways were "grouped" into four large companies in 1923, the Southern Railway became the undoubted pioneers of electrification. Having standardised on 660V (later upped to 750V) DC supplied through a third rail, they made a concerted effort to electrify their entire network: by 1939 the "Southern Electrics" covered almost all of south London, running as far afield as Brighton, Eastbourne, Hastings, Guildford, Portsmouth and Reading.

But a committee in 1921 had recommended the national standard should be 1,500V DC through overhead wires; a few lines were electrified using this system by the LNER, such as the Woodhead route between Manchester and Sheffield, but the Great Depression and the Second World War prohibited much progress being made. Overhead wires finally started appearing on the commuter route from London Liverpool Street to Shenfield and Southend Victoria in 1949.

By the time of the 1955 Modernisation Plan, technology had moved forward considerably, and 25kV (25,000V) AC became the national standard for all new electrification schemes. Over time, all the remaining 1500V DC overhead wires were converted to 25kV AC, except those on the the Woodhead route where the line was controversially closed in the 1980s. More importantly, the 1960s and 1970s saw the entire 400-mile West Coast Main Line between London and Glasgow electrified at 25kV AC with overhead wires.

As with many things on the railways, the story at this point inevitably gets tied up with politics. After the success of the WCML electrification and various suburban electrification schemes around London and Glasgow in the 1970s, British Rail wished to embark on a rolling programme of electrification, whereby all the major main lines would be gradually electrified over the course of 20-30 years. Unfortunately, the plan was formulated in 1981, and the Conservative government of the day declined to proceed with the rolling programme in full. To its credit, though, it did fund the electrification of the East Coast Main Line between London and Edinburgh, completed by 1991.

This relatively slow pace of electrification is in marked contrast to other countries in Europe, notably Germany, where they forged ahead with much electrification even before the Second World War, and were more aggressive in replacing steam directly with electric trains, rather than just building diesel engines. Over half of the French, German and Italian rail networks are electrified, while in Belgium and the Netherlands nearly three-quarters of the network is electrified.

Any long-term plans British Rail might have had for electrification were well and truly dashed when, in 1994, the railways were privatised and fragmented. The industry was left without a body like the British Railways Board to advocate for a coordinated national approach to things like electrification. As a result, between 1991 and 2010 only nine miles of railway were electrified: the short link between Stoke-on-Trent and Crewe received overhead wires as part of the West Coast Route Modernisation, to provide a diversionary route for electric trains while other lines were rebuilt.

It has taken the railway network most of a generation to find its voice again. Indeed, as recently as 2007, John Armitt, then chief executive of Network Rail, said that electrification was just another interface to go wrong: too often the overhead wires come down and cause disruption; better to not put them up at all and have a quieter life. In less than five years, though, the view has turned full circle and the government is currently demanding electrification faster than Network Rail can deliver it!

When the Thameslink Programme was approved in 2007, the initial intention seems to have been that the electric trains would simply be moved to a different line with older trains, permitting some of the oldest electric trains to be retired. This "cascade" of trains has long been standard practice, as it allows more than one line to benefit from better trains while only building one new fleet.

But in July 2009, instead of simply shuffling the trains about existing electrified lines, the then-Transport Minister Andrew Adonis approved a plan to electrify new lines in the north-west and the Thames Valley. Once the new trains had been built, the old electric trains from Thameslink would move to the newly-electrified lines; as a result, the lines could be electrified without the cost of building new electric trains. This significant saving is probably the only way electrifying some of the lines could be justified: the cost of new electric trains is not to be underestimated.

The plans were put on hold when the coalition government took over in 2010, but within a year it was back on track. Indeed, the present government has taken a huge liking to electrification, and rather than a rolling programme we seem to be heading for a "big bang", where a huge number of lines will be electrified by 2020:

• a triangle of routes in North-West England, namely the Liverpool-Manchester, Liverpool-Preston and Manchester-Preston lines, as well as the branch from Preston to Blackpool North, will be electrified by 2016;
• the Trans-Pennine route from Manchester to Leeds, York and Selby will be electrified by 2018;
• the Edinburgh-Glasgow Improvement Programme (EGIP) will see the main route from Edinburgh to Glasgow (via Falkirk) electrified by 2016, with other suburban routes in the central belt following by 2019;
• the Great Western Main Line (GWML) from London to Oxford, Newbury, Bristol and Swansea will be electrified in stages from 2016 to 2018;
• following on from that, the Valley Lines in south Wales will be electrified by 2020;
• the Midland Main Line (MML), already electrified between London and Bedford, would have its wires extended from Bedford to Corby, Nottingham, Derby and Sheffield in stages from 2017 to 2020;
• in a project dubbed the "Electric Spine", the lines from Southampton to Nuneaton and Bedford would also be electrified to create an electric freight route for containers from Southampton to the north of England and Scotland.

Let's see that on a map:

British railway network, showing planned electrification by 2020

In theory all of this should be electrified by 2020. However, some parts of the plan are further advanced than others, and you'll note I didn't put a date on the completion of the Electric Spine: it seems as if the Department for Transport saw an idea that Network Rail put forward for possible future electrification and said "ooh, yes, we like that", and approved it before Network Rail had really had a chance to scope out to the project. Nonetheless, the rest of the electrification schemes are proceeding apace, with part of the Liverpool-Manchester line already open to electric trains.

While electrification provides significant benefits - reduced running costs, faster journeys - it doesn't always provide a "step change" without other investment, and the most successful electrification schemes are usually accompanied by changes to track layouts and signalling to unclog bottlenecks in the route.

For example, when the southern part of the WCML between London and Manchester was electrified in the 1960s, a flyover was built at Rugby to allow trains from Birmingham to head to London without interrupting the flow of northbound trains. That one bridge did nearly as much for improving capacity as electrification alone did; together with major rebuilding projects at London Euston and Birmingham New Street stations, they yielded "total route modernisation", and provided for a doubling of traffic on the WCML between 1962 and 1975.

Each of the major electrification schemes planned comes along with various capacity improvements. In the next three posts, I will look in turn at the three big drivers of change on England's railways outside London:

• the "Intercity Express Programme" (IEP) will introduce brand-new Hitachi Super Express trains to the GWML which, combined with electrification, the construction of Crossrail, and the complete rebuilding of Reading station, will totally transform the Great Western Main Line;
• the Northern Hub, encompassing the electrification in the north-west of England and across the Pennines, will unlock capacity through the congested approaches to Manchester Piccadilly and transform rail travel across the north of England;
• the Electric Spine, which technically includes the MML electrification, will (hopefully) transform the future of freight movements by rail across the country.

In the meantime, if you'd like to learn more of the history of electrification in Britain, I'd recommend two booklets on the electrification of the WCML: the first was published in 1966, and the second was published in 1974. Both are preserved on the Railways Archive, a fascinating treasure trove of historical documents from 1830 right through to the present day.

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