The following has been prepared on a collaborative basis with contributions from several people including employees of London Underground.

Will a Turnham Green stop really cost £30mn?

The £30 million number quoted by LUL is made up of two principal items trains and signalling. Two trains at £10mn each and £10mn for signalling. A new train would indeed cost £10 million and its not like buying a new car. Typically LUL orders their trains in batches so it is unlikely that they ever would just buy new trains for one service enhancement.

However when you they are upgrading the line they would achieve a certain frequency by buying a certain number of trains. This frequency would be reduced if there was a stop at Turnham Green and two extra trains would need to be added to the order. The alternative would be to take a marginal reduction in your target frequency. Therefore it is technically true that a Turnham Green stop would "cost" £20 million. On the other hand you have to set the marginal reduction in frequency that would be caused by not buying two trains against the benefit to the network of having a stop. Remember this eventuality only arises well into the future when they are actually purchasing a new batch of stock for the Piccadilly line.

At the moment no extra trains are needed because LUL are operating well short of their target of 30 trains per hour (and therefore must have spare capacity) This situation is likely to continue for the next few years at least and possibly will only be completely sorted out when there is a general upgrade of the line..

The signals in this section of the line are quite antiquated and due for an upgrade. It is not clear whether the £10 million quoted is cost of this upgrade in total. It does seem unlikely that the signalling change necessary to maintain frequencies on the line if a stop at Turnham Green would cost that much. One former LUL employee has estimated that the cost would be around £100,000 for the enhancements necessary in isolation but if a Turnham Green stop was incorporated into the general upgrade then the marginal cost would effectively be zero.

Would LUL need to buy two new trains to introduce a stop today?

At the moment no, because LUL are operating well below their target frequency of 30 trains per hour.

It is possible they would need to buy new trains just to operate at 30 trains per hour even if there wasn't a stop at Turnham Green.

The current stock of Piccadilly line is 86.5 trains. It is estimated that 85 trains would need to be operational every day to have a train stopping in the central section of the line every 2 minutes. In practise about 9 more trains would be needed.

One solution to this is possibly to use the Jubilee line stock that was mothballed when the extension was built. This is not particularly old - it was brought into service in 1986 and it could operate on the Piccadilly line. There are 15 of these trains available which could possibly allow a 30 trains per hour service to be achieved with a stop at Turnham Green.

Would the frequency of Piccadilly line trains really drop from every two minutes to every three minutes?

No - because Piccadilly line trains are actually only operating every two and a half minutes at peak times according to their own timetable. This is because their existing systems are unable to handle greater frequencies. In fact the timetable is being altered to reduce frequencies at off peak times because of the timetable has proved too demanding for the network.

Okay, would the frequency of Piccadilly line trains drop from two an a half minutes to every three minutes?

Almost definitely yes. Existing signalling at Turnham Green is not sophisticated enough to hold a train very close to the station so they have to wait a long way back. This would lead to bunching of trains and reduce frequency. In part this might be mitigated by the fact that there is often a hold-up at Acton Town because of a change of drivers so the delay would occur whether there was an extra stop or not. The only way around this is improved signalling and how feasible this is remains unclear. There seems to be no good reason why, as part of a general upgrade, the specification for a stop at Turnham Green could not be introduced. Under the Mayor's plans this upgrade would occur in 2004. As was stated above to introduce signalling specifically for this change probably wouldn't cost £10 mn but that is not to say that the actual cost wouldn't be prohibitive.

If a signal upgrade was possible what would be the impact on frequencies?

Assuming no extra trains were brought into use then there would be an estimated 5% reduction in frequency at peak hours. This translates into an estimated 6 extra people in each carriage of the train. If extra trains were brought on then the amount of people on each train would remain unchanged.

When will the trains ever stop?

If the signalling was relatively cheap and easy to upgrade for a stop at Turnham Green (there is no conclusive evidence that this is the case) LUL would probably be able to introduce a stop with relatively little impact on frequencies very soon.

However they may feel that the introduction of a stop now would leave them short of stock when they manage to upgrade their systems to operate at 30 trains per hour (i.e. every two minutes). Although theoretically they could use the Jubilee stock there maybe a good reason why this is impractical. This would mean that they would either have to plan for a reduced level of frequency in the future or take away the Turnham Green stop at a later date.

In the longer term signals will be upgraded and new trains will be bought regardless whether there is a stop at Turnham Green. The management of London Underground seem to be entirely focussed on frequency which may be a result of the way they are assessed. This is not a bad thing in itself because obviously more frequent trains means less overcrowding and a safer network. However from this perspective stopping at Turnham Green becomes a pure cost i.e. it reduces your return on investment because you need more trains to meet you target frequencies.

It will be more difficult for LUL to maintain this practise of focussing on one variable when they come under the auspices of the GLA. Whilst the GLA will be keen to see LUL increase train frequencies they will be more sensitive to other passenger needs such as a stop at Turnham Green.

If the GLA felt that the benefit of a stop at Turnham Green outweighed the impact on frequencies then there is no reason that it couldn't commit in principle to a stop being introduced as soon as Transport for London (the GLA body that will oversee the tube) takes over. How soon that would lead to a trains actually stopping remains unclear but 2015 seems an unlikely date.

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