Thursday, 11 September 2014

What is... the Electric Spine? (Or, Why Freight Trains Matter to Everyone)

The "Electric Spine" is a plan to electrify two key rail arteries from the port of Southampton to the north of England (via Nuneaton and Sheffield), creating an electrified trunk route avoiding London, principally for use by freight trains. The plan is, as yet, still not finalised; but it promises to have a huge (yet also subtle) impact across the country. So while this blog usually focusses on passenger trains, for this post I'd like to delve into the world of freight trains, and explain why we're spending over a billion pounds so that freight trains can run a bit faster...

Once upon a time, almost all freight traffic in Britain was moved by rail. While the vast majority of it is now hauled by lorries instead, for some traffic (e.g. coal) rail is still the "right" way to move it around the country. This is especially true of long-distance flows: for example, for taking containers from Southampton to Scotland, or cars from Merseyside to Dagenham Dock, rail has the advantage of bulk and speed that road just can't match. Indeed, container traffic has seen a marked shift from road to rail in recent years, and the challenge for the rail network is how to accommodate it.

Unlike passenger trains, which can be broken down into discrete services, even the destinations of freight trains can vary from day to day. Passenger trains between London and Birmingham are completely segregated from, say, passenger trains between London and Dover; in that sense, the electrification of the passenger rail network can be - and is - broken down into discrete chunks, one main line at a time. Freight trains, though, are much less frequent and tend to run to a wide variety of destinations, over a variety of different routes according to where there's capacity.

By its very nature, then, the network used by freight trains is huge and sprawling: indeed, it's quite hard to find a significant part of the network that isn't used by freight trains at all. As a result, while some freight trains running on key main lines can be hauled by electric locomotives, the vast majority of freight trains remain hauled by diesel engines, even when some of the route has electric wires, because having to stop and change engine takes too much time. And that's unlikely to change until a significant portion of the freight network is electrified.

So what is driving plans to try and do just that? The key advantage of electric freight trains over diesel ones is acceleration. Freight trains are mostly limited to 60mph, and while some container trains can manage 75mph, electric haulage can't really improve that. What it can do, though, is dramatically improve acceleration, so that when a freight train has to run between two passenger trains, it doesn't need as large a gap. Quicker acceleration, more capacity. Crucially, though, not just capacity for freight trains but also for more passenger trains.

This is especially true on mixed-traffic lines, where passenger and freight trains have to share the same tracks. For example, while the south end of the WCML has four tracks, north of Preston it's two tracks all the way to the outskirts of Glasgow. In particular, over Shap in the Lake District, where the WCML runs roughly parallel to the M6, the two-track line threads its way between the hills with gradients as steep as 1 in 75. For a 4,000-tonne freight train, 1 in 75 is a big problem! However, while diesel trains are limited by how big an engine they have and how much fuel they can carry, electric trains are basically limited only by how much current they can draw.

The difference between electric and diesel freight trains over Shap can be summed up as follows: from Preston to Carlisle (about 90 miles), a freight train hauled by an electric locomotive generally won't have to stop to be overtaken by faster passenger trains, while a diesel train almost certainly will. Having to have the freight train slow down, pull into a loop, wait to be overtaken, and then start up again costs a lot of time and capacity; converting diesel freight trains to electric over Shap would significantly increase capacity on this very mixed-traffic line.

The "Electric Spine" is the first major project in trying to convert freight trains to electric haulage: the broad intention is that almost all long-distance container trains to and from the port of Southampton will be able to run with electric traction. At this point, though, while the project is committed by the government, it's still being developed by Network Rail, and is unlikely to be fully complete before 2025. Indeed, more than any of the other "big projects" I've discussed recently, the Electric Spine poses the biggest unknowns: there are things in the plan that have never been done before.

Let's return to electrification in general (see my earlier post if you need a refresher). There have been many different voltages and both overhead wires and various forms of third rail in use for electric trains over the years, but two systems remain in widespread use in the UK: 750V DC third rail, mainly south of London, and 25kV AC overhead wires, mainly north of London. Because most passenger services are self-contained, most electric trains only need one kind of electric equipment, and for the small number of services (mainly Thameslink and London Overground) which use both, the trains can be fitted with both systems.

Both systems have advantages and disadvantages: third rail systems are better suited to dense suburban networks, while overhead wires are better suited to long-distance traffic. That said, most would agree that overhead wires are better than third rail - and if the network south of London were being electrified today there is no question that it would be done with overhead wires. The principal problem with third rail is that, because the rail is so close to the ground, the voltage can't really be made higher than 750V. (The National Grid uses 275kV DC to transmit electricity around the country, but the wires are high in the air.)

In order to provide enough power through the third rail, the current has to be higher than it would in overhead wires (power is current times voltage), and as a result a lot of power is lost in transmitting it down the rails; this means third rail requires lots more substations to provide enough power. In particular, providing enough power through the third rail to permit electric locomotives to haul freight trains is hideously expensive, and while it can be done, there are only a couple of routes which have been upgraded to provide enough power, namely those connecting London to the Channel Tunnel.

And here we encounter the major problem with the Electric Spine: Southampton is already electrified... with third rail. The plan for the Electric Spine thus calls for something which has never been done on this scale: the conversion of the line between Basingstoke and Southampton from third rail electrification to overhead wires. While this means freight trains will be able to run on overhead wires all the way to the docks at Southampton, the existing passenger trains which run between London and Weymouth would be required to change from third rail to overhead wires at Basingstoke and back again at Southampton.

For the sake of convenience to passenger trains, you might reasonably ask whether you could simply have both overhead wires and third rail between Basingstoke and Southampton. Clearly it has to be possible over short distances, otherwise trains would never be able to change from one to the other. However, in the section with both overhead wires and third rail, both systems must be carefully insulated from each other in other to prevent current straying from one to the other. As such, the existing third rail equipment would have to be heavily modified; it's certainly not as easy as just adding overhead wires on top of the existing third rail.

In any case, part of the justification for converting the line between Basingstoke and Southampton is that the third rail equipment, which was installed in 1967, will need to be replaced shortly anyway. Given that 25kV AC requires fewer substations than 750V DC, it is in fact cheaper - at least as far as the infrastructure is concerned - to replace the third rail with overhead wires. But this ignores the fact that the existing electric trains, run by South West Trains (SWT), would require conversion to work on overhead wires as well as third rail. These trains are about 10 years old, and most (the Class 450s) should be straightforward enough to convert (though the Class 444s may require more work).

And here is where the ugly truth of the privatised, fragmented British railway system rears its head: who pays? The Department for Transport are happy to pay Network Rail for the work to the infrastructure, but it is not clear who will pay for the conversion of the trains. The trains are operated by SWT, but are in fact owned by the rolling stock holding company Angel Trains. Why should either SWT or Angel Trains pay to change their trains because of Network Rail's infrastructure changes?

The issue is yet to be resolved, and it's still not clear whether the line between Basingstoke and Southampton will actually be converted. I suspect it will, but I suspect the government will have to pay for the conversion of the trains as well. However, if any of the electrification projects were to run over-budget, the quickest way to save money would be to kick the whole Basingstoke-Southampton conversion into the long grass.

The rest of the Electric Spine can be broken down into four distinct chunks:
  • The section between Basingstoke and Oxford, via Reading, will be electrified as part of the Great Western Main Line electrification, associated with the Intercity Express Programme (see my earlier blogpost) - at least, the Reading-Oxford part will; exactly what will happen with Reading-Basingstoke isn't clear.
  • The section between Oxford and Bedford is unusual in that part of the line that will be electrified isn't open yet! The "East-West Rail Link" is soon to be reopened; whether it will have overhead wires from opening (in 2017) or whether it will follow a few years later (by 2019) remains unclear. (See also my earlier blogpost about a railtour along part of the East-West line.)
  • The section between Bedford and Sheffield amounts to electrification of the rest of the Midland Main Line (MML), the section between London and Bedford having been electrified in 1981 for suburban trains. This section will herald the biggest changes for passenger trains too, allowing the existing diesel trains running between London and Nottingham, Derby and Sheffield to be replaced by electric trains.
  • The section between Oxford and Nuneaton, which will probably be the last part to be completed (apart from Basingstoke-Southampton), will link Southampton to the West Coast Main Line at Nuneaton, allowing electric trains to run all the way from Southampton to Manchester, Liverpool and Glasgow. I wouldn't be surprised if this got pushed past 2020 (and it would make another easy target for cuts).
While this is a good start to an electric freight network, that's all it is: a start. For one, it's missing a key connection from Sheffield to the electrified East Coast Main Line at Doncaster. But it also leaves the other major deep-water container port - Felixstowe, in Suffolk - just twelve miles from the electric wires at Ipswich. Electrifying that branch could probably do as much for container freight as the whole Electric Spine project.

One of the other major freight projects in recent years has been to increase the number of trains from Felixstowe which can avoid London to get to the north of England and to Scotland. Currently much of the traffic runs through London: fitting freight trains through London is a perennial challenge, with most London Overground routes in fact being freight routes that some would argue would be more efficient without any passenger stations on them! In order to relieve the pressure, tunnels and bridges have been enlarged to permit container trains to run from Felixstowe to Nuneaton via Ely, Peterborough and Leicester. If that line could also be electrified, then we'd start to make major inroads into converting at least container trains to electric traction. It seems that that, however, will have to wait for Southampton to have its turn first.

Ultimately, the point of the Electric Spine is to increase capacity - both for freight and passenger trains - by using electric locomotives, with their impressive acceleration, to speed up freight traffic across the country. On the one hand, this should mean fewer lorries on the roads, making road travel easier for everyone. On the other hand, this will mean more capacity for passenger trains, and fewer delays caused by late running freight trains (hopefully). It sounds like a win for everyone - and it should be - but the devil, as usual, is in the detail. For now: watch this space.

Previous post: What is... the Northern Hub?


  1. What is the structure gauge on this line? Could you, for example, run double decker trains from St Pancreas to Sheffield?

  2. The Electric Spine is a really good idea. Increasing a train’s capacity by using electric locomotives for a freight or a passenger train is a great advancement. Delays in travel will definitely be diminished if it were to be implemented. Anyway, thanks for sharing this post with us, Dave!

    Kellie Taylor @ Aim Dynamics

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