A Question Of Carriages: Increasing Services on the South West Main Line


One thing that swiftly becomes apparent when looking at the recent London and South East draft RUS is how the proposed solutions to capacity problems are very different for the different lines, which all have their own particular features. In the lines examined so far there seems to be a positive way forward to overcome these problems in situations where they could become significant, although it does seem that the Brighton Main Line would face a relatively small capacity ‘gap’ that has no easy solutions.

We now look at the South West Main line which is basically the area covered by South West Trains except for the Windsor lines which we looked at last time. All these services pass through Wimbledon. These in turn can be conveniently divided into inner (suburban) services and an outer services (outer suburban and longer distance). They tend to terminate in the eastern side of Waterloo station.

There does not seem to be too much of an issue relating to inner suburban services. The committed plan is to increase these to 10-car trains which it believed will be adequate for many years to come. However, there is also the dire warning that, if it turns out that yet further capacity is needed , “it is emphasised that providing 12-car suburban capability at London Waterloo is complex and high cost.” One presumes they are talking about the plan to extend the platforms onto the concourse and relocate the circulating areas below the tracks, as is done at St Pancras.

For the outer suburban services and beyond there is no easy fix, as these are services which are already operated by 12-car trains. Unfortunately it is here that a significant “gap” has been identified. The phrase “running out of options” springs to mind. The RUS makes three suggestions – one of these it does not recommend, one requires further analysis and one is “potentially needed in the long term if other options cannot be identified.

The least favoured option is double-deck trains. Increased dwell times are cited but the main problem is the “extremely disruptive and expensive” need to regauge tunnels and raise bridges. There is also doubt expressed that it would actually do much to solve the problem. Certainly a double-deck 20 metre long carriage is going to have a fair portion of its space wasted in the end vestibules.

The next option is to eke out an extra four train paths per hour. This would bring capacity to 28tph, which is really taking it to the maximum. Just to achieve this is going to require the remodelling of Waterloo station throat and approaches and grade separation of Woking junction as well as other infrastructure changes. The obvious disadvantages are that there would now be no slack whatsoever in the timetable so recovery from even a minor disruption would be very difficult. There is no way you can build on this solution once implemented. However, the reason the RUS is lukewarm to this is that it only goes halfway to resolving the overcapacity issue. Even when implemented you would still have a problem.

The final suggestion is to run 16-car trains. In recent years, trains have tended not to exceed twelve carriages. An exception, of course, is Eurostar – but the requirements there are very, very different. Now that trains tend to be fixed formation there really is no opportunity to just add an extra carriage on an ad-hoc basis to make up a longer train to cover a particular heavily-loaded service. As a result, around twelve carriages has been the maximum that has until now made sense for domestic operation.

The idea of running sixteen carriages on a suburban or outer-suburban service is certainly not new. In the heyday of EPB stock, Southern region looked at running 16 carriages (4 units) on the Brighton line. There, it was not the power supply or the longer platforms that was the main problem – it was that it was realised that, as the signalling was designed with a maximum of 12 carriages in mind, it meant that a longer train could actually lead to further restrictions in capacity as the signalling and track layouts would no longer be optimised. Of course the layouts could have been redesigned, but this would then put further restrictions on all train movements regardless of the length of the actual train. The lesson learnt is that you need to run at least a fair proportion of your services at the maximum length that the track and signalling are designed for, otherwise, by allowing for longer trains than you are actually running, you could actually end up reducing overall capacity.

Sixteen carriage trains is not generally put forward as a solution to the railway capacity problem in the UK. However on the South West Main Line there probably three things in its favour:

i) The empty Eurostar terminal at Waterloo could very easily handle the long trains and the number of people arriving at the terminal at the same time would not pose a major problem as the infrastructure has been designed to handle this.

ii) The plan is to combine two eight carriage trains at an outer-suburban stations such as Basingstoke or Woking. If they run non-stop you only actually have to lengthen the platform at one or possibly two stations although the lengthening at those stations would be substantial – realistically we are talking about between 85 and 100 metres by the time we allow extra space for coupling and uncoupling.

iii) You would not suffer too much from the issue of limiting the signalling or track capacity. This is because this tends to be more of a problem when the trains are stationary and occupying track circuits for a relatively long time. A long train speeding along the line is not going to have that much of a negative impact.

The problem with the proposal for longer trains is that the long ex-international platforms at Waterloo are on the west side of the station whereas the trains involved currently terminate on the east side. What is needed is a flyover in the Clapham Junction area. The RUS does not go into any detail into this and as always the devil is in the detail. There are no suggestions as to exactly where the flyover would be or whether the trains would call at Clapham Junction.

In summary, for the longer distance services the RUS offers three options which are presented as the no-good solution, the short-term partial solution or the long-term proper solution. It emphasises that for the latter two “further analysis is required”. Of course there is nothing to stop the some of the infrastructure enhancements required for the partial-solution being implemented prior to the implementation of the long-term solution. The RUS gives the impression here that it really is a case of: “Here are the three options. We are convinced one of them is rubbish but we really are not yet sure which of the other two options is the better one”. Longer trains would be interesting and would, if introduced, undoubtedly cause new problems that had not been anticipated or fully appreciated, they may, however, prove one of the few solutions. If that turns out to be the case though, then one must feel sorry for the people with heavy luggage who are in the last carriage as they arrive at Waterloo – and then realise just how far they have to walk just to get to the main station concourse.

Written by Pedantic of Purley