One of the rules of LR is that the more innocuous the title, the more interesting a TfL committee paper is likely to be. Additional New Rolling Stock for London Overground for the October 2017 Programmes and Investment Committee certainly meets this criterion.

A time-limited offer!

By way of introduction, the paper explains that additional rolling stock is needed for both the Barking Riverside Extension, now that it has been authorised, and to increase the service on the East London Line (ELL) to 20 trains per hour (tph) from 16tph. If these trains are not ordered by 26th October 2017, then they cannot be purchased at existing prices as an add-on to the existing order for 45 Class 710 4-car 25 kV AC trains, 14 of which are also 750 DC capable. The Class 710s are due to replace existing rolling stock on the London Overground Liverpool St services, Romford – Upminster shuttle, the Gospel Oak-Barking line (GOBLIN) and partially replace trains on the Euston – Watford Junction line (Watford DC) which enables some strengthening of services elsewhere.

The paper makes it clear that it isn’t just the purchase price that is an issue – it is the leasing terms as well. To benefit from existing leasing terms, it is highly desirable to add to the existing order before the deadline. It seems to be a case of ‘buy all we can afford now’.

One-off opportunity!

In the case of the ELL, what is far more interesting is how it has become possible to increase the frequency by removing signalling constraints long before anyone imagined it would have happened and at little, or no, cost to TfL.

To quote the paper:

In the 2016 Autumn Statement the Chancellor announced a £450m Digital Railway fund for trialling digital signalling technology, expanding capacity, and improving reliability. The strategic outline business case for the ELL 20 trains per hour project has been shortlisted to receive funding from this fund. Funding of £6m has been received to develop the project to outline business case but a final decision is not expected until spring 2018.

So an unexpected opportunity has arisen to both buy trains at a cheaper price than they would otherwise cost and to have the ELL signalling upgraded at no cost to TfL. Despite TfL being strapped for cash, it must be hard to resist such an opportunity. Indeed, one could even argue that because TfL is strapped for cash it is even more important to take advantage of such an opportunity while it exists.

Stabling comes (almost) free!

It gets better still. Even the cost of stabling the trains (at the east side of the tracks south of Norwood Junction station) is thought to be mostly covered by costs Network Rail are due to incur anyway and an application to a separate fund can be made to cover the difference.

So far everything looks rosy. But, of course, in real life, things never work out this perfectly. The biggest problem is one of timing, but there are others as well. Furthermore, as you can see from the above quote, a final decision on the Digital Railway proposal is due in Spring 2018. This leaves TfL with something of a gamble to make, for it is not explained what will happen if they place the order for the extra trains, only for the Digital Railway resignalling to not go ahead.

Indeed, the paper is clearly about the purchase of the trains and the need to delegate authority for this to take place, but it is surprisingly lacking in detail covering the full background. For example: which two of the four East London Line southern branches would benefit from the improved service? There is also a complicated train cascade plan. Some of this makes immediate sense, but other parts appear to do so if one knows the detail of existing plan which is reliant on the initial order of Class 710 units.

Buy for one line – use for two!

Just to add to the complexity, also included is a plan to temporarily improve services on the West London Line (WLL). This would use trains not immediately required on the East London Line. But, again to quote from the paper:

An enhanced frequency, to provide congestion relief, would be operated between Clapham Junction and Willesden Junction and/or Shepherd’s Bush. A plan will need to be developed to maintain services on this line when the trains are required for the ELL.

This says to the Committee that London Overground will be back for some more money. That money will be for a plan, to be implemented by May 2021, to enable the frequency of the WLL service to be maintained. They just won’t yet say what that plan is.

Moving on from this, we look now at the three aspects of this proposal.

Barking Riverside extension

This is by far the simplest proposal and the one that is the easiest to understand. An extra two trains are required to extend the 4tph GOBLIN to Barking Riverside. These have to be 4-car trains because there is no prospect of making GOBLIN suitable for 5-car trains in the short or medium term future (some work has been done in this area, but only at selected stations).

It is quite important to ensure that there is homogeneous stock on this line to simplify both operation and maintenance. So, realistically, as soon as the Riverside extension was confirmed it was almost inevitable that an add-on order for the trains would be required.

The extension should be in operation in 2021. This leaves the trains without a purpose for around three years prior to that. London Overground hope that they can sub-lease them to another Train Operating Company (TOC) during this period.

West London Line frequency enhancement

London Overground have a long-held desire to increase the frequency on the WLL from 4tph to 6tph. They also aspire to another 2tph (at least) from Clapham Junction continuing to Stratford, to further increase the frequency on the North London Line (NLL). This would enable 10tph on eastern end of the North London line. This is due to be implemented with with main order of the new Class 710 stock.

What, it is suspected, London Overground would really like is to have 6tph from Richmond to Stratford and 6tph from Clapham Junction all the way to Stratford. Unfortunately, the additional trains to Stratford would appear to rely on freight, travelling between East London and the West Coast Main Line, using the route via Gospel Oak instead of via the NLL. Until that actually happens, sometime after the electrification of the GOBLIN, such an intensive service on the NLL can only be a dream.

Typical hourly pattern currently on the West London Line, with the WLL trains highlighted in orange. Hourly Southern trains from East Croydon to Milton Keynes highlighted in green.

What is currently possible on top of already proposed improvements is an additional 2tph from Clapham Junction to either Shepherd’s Bush or Willesden Junction. Shepherd’s Bush would appear to be an unsatisfactory place to terminate a portion of trains from the south. The move involves around 500m of time-consuming wrong-way running from the relevant crossover into the southbound platform. Alternatively, one can carry out a time-consuming manoeuvre and go further north once out-of-service and turn back at North Pole turnback siding. Nevertheless, Southern trains appear to manage a turn-around at Shepherd’s Bush on RMT strike days when they are unable to go further north without a guard on board.

Willesden Junction would seem to be a much more desirable place to terminate. This would also fit in better with the existing service, which has 2pth from Clapham Junction to Stratford and 2tph to Willesden Junction.

It is presumed that there is not an issue terminating 6tph in platform 1 at Clapham Junction.

As suggested above, this seems to be the precursor of some bigger plan to be implemented in 2021. Whilst money at TfL is tight, London Overground predict that the demand is there so the improvements are necessary. They may be slightly encouraged by the fact that London Overground trains are more-or-less off-the-shelf. As a result, they tend to be much cheaper than Underground trains despite having significantly more capacity per carriage than deep level Tube stock. Also, depot modification and expansion seems to be cheaper and less problematic. If the demand is there, you get more bang for your buck investing in rolling stock for London Overground rather than London Underground.

East London Line

The ELL is well-known for operating at capacity at certain times of the day. Of particular concern are stations such as Honor Oak Park in the morning peak, where passengers cannot always board the first Overground train that arrives. The service to Clapham Junction is also busy for much of its length.

For many years there has been talk of running an extra 2tph ‘pixie busters’ (‘Passengers In eXcess of Capacity’, or PIXC to its friends) on the Crystal Palace branch in the peak period. Indeed, it is a bit of a mystery why this hasn’t already happened, as the trains are available (they are currently designated as ‘hot standbys’). The main reason for this not taking place seems to be the issues at London Bridge during its redevelopment.

There is also a long-term aspiration to run 6tph to West Croydon instead of the current 4tph. This is currently not possible. Both because of a lack of capacity in the Selhurst triangle area (Windmill Bridge and associated junctions) and because it is not possible to terminate 6tph of Overground services at West Croydon. Furthermore, there is no simple way for a train on the branch south of New Cross Gate to terminate short of West Croydon – other than by diverting to Crystal Palace.

If the necessary improvements were to be made as part of the East Croydon upgrade in the 2020s then 6tph would be possible to West Croydon. The terminating capacity issue can be resolved by reinstating a track west of Wallington (two stops west of West Croydon) to give a central terminating siding for 3tph – leaving 3tph still to terminate at West Croydon.

The fourth branch of the East London Line is the one to New Cross. This is not especially heavily taxed though trains can be full on arrival and departure from New Cross – but not to the extent that people get left behind.

5tph per branch – too simple

If you increase the service from 16tph (4tph per branch) to 20tph then you might assume that this means 5tph per branch. We can be almost certain, however, that this is not going to happen. Aside from the problem running extra trains to West Croydon, trying to fit trains 12 minutes apart on Southern’s network with trains generally every 10 or 15 minutes is just going to be a nightmare.

So where will the extra 4tph go? 2tph will almost certainly go to the Crystal Palace branch. It is known to be doable. This would also help relieve the Sydenham – New Cross Gate corridor in the morning peak.

Equally, we can conclude that the New Cross branch, though probably capable of handling 6tph, doesn’t need extra trains. As further evidence for this not being a branch on which an increased service is planned, the number of extra trains to be ordered is far more than would be required if the New Cross branch were to receive an increased service.

So, we can fairly safely conclude that the proposal is for the service to be increased to 6pth on both the Crystal Palace and the Clapham Junction branch. At Crystal Palace, where there are two dedicated terminating platforms available, we can be confident that the terminus can handle the increase in services.

At Clapham Junction, there is less certainty that the relevant platform, platform 2 can handle 6pth. One problem is the long single-line approach – slightly longer than at platform 1. A further complexity, which we will cover, is that you cannot easily create a timetable where the service will be every 10 minutes. There is no real reason to believe that having only one terminating platform for this service is a problem though. Even if it is, there is the option of diverting 2tph to Battersea Park.

The slightly messy timetable

Welcome though the extra capacity will be, with 20tph on the East London Line, the timetable will be a bit messy. With two branches operating 6tph and two operating 4tph things are bound not to be perfect.

Almost certainly, the service will operate on a pattern repeating each half hour with trains three minutes apart in the central section. For those that do not want to be bogged down by analysis, skip to the second table showing frequencies headed “A better pattern of branch frequencies”.

Here is one argument to try and find the best timetable. As we shall see later it is flawed but that just goes to show how tricky it can be to produce a decent timetable with multiple branches and different frequencies on those branches.

Imagine being on the southbound platform at Surrey Quays. Whilst not a rigorous proof of the best option, working out roughly what happens can be logically argued as follows:

Arbitrarily you can assume that one of your 6pth branches is the first train. Let us say this is the Clapham Junction branch

A bit of thinking reveals that at some stage a train on one of the 6pth branches must be followed by a train on the other 6tph branch. Without any real loss of generality, it might as well be assumed that a Crystal Palace train follows

Equally, the third train must be one of the trains on the 4pth branch otherwise the more frequent branches get too frequent, and the less-frequent branches are not frequent enough. It could be a West Croydon train but that would lead to two consecutive trains going as far south as Sydenham, so it makes sense to assume this is a New Cross train.

It is now 9 minutes since the previous Clapham Junction train left. They ideally should be 10 minutes apart but that is not possible as 10 is not a multiple of 3. So the fourth train should logically be our second Clapham Junction train

By the same logic, our next train needs to be a Crystal Palace train

There hasn’t yet been a train to West Croydon. It isn’t desirable for this to be one following a Crystal Palace train but this turns out to be unavoidable

Another train is needed to run to Clapham Junction

Similarly, another train is needed to run to Crystal Palace

It is 18 minutes since a train ran to New Cross so another train is needed to run there

There has only been one train to West Croydon in the past 27 minutes and that is a 4tph service so another train is needed to run there

A first attempt at establishing branch frequencies

The above crude analysis will provide the following frequencies on the branches over an hour:

Branch Service Pattern Trains Per Hour Clapham Junction 9-9-12- 9-9-12 6 Crystal Palace 9-9-12- 9-9-12 6 New Cross 18-12-18-12 4 W Croydon 12-18-12-18 4

In reality, as is the case today, these exact intervals might not apply along the entire length of the branches due to the need to wait at junctions or run early to avoid that need. In order to maximise reliability, however, and reduce the buildup of crowds there will be a strong desire for a regular interval in the busy section that operates at 20tph.

In fact there is a flaw in the above argument presented in the article as originally published because not all possibilities are considered. As reader Tom has pointed out, you can actually do better and retain the even 15 minute interval on the two branches with 4tph. Possibly the best way to envisage this is to assume that this is possible and that trains on the two branches with 4tph do not follow each other. Then you for every five trains you have one to New Cross, one to West Croydon and with suitable juggling around with the remaining three paths available you can achieve a combination of 9 and 12 minute intervals on the two branches with 6tph.

What Tom points out is that you can run a better service with an 30 minute repeating cycle. The first 15 minute pattern would look something like this:

New Cross

Crystal Palace

West Croydon

Clapham Junction

Crystal Palace

and the second 15 minute pattern would be the same but with the order of the two 6tph branches transposed i.e.

New Cross

Clapham Junction

West Croydon

Crystal Palace

Clapham Junction

A better pattern of branch frequencies

This produces a better pattern for the New Cross and West Croydon branches

Branch Service Pattern Trains Per Hour Clapham Junction 9-9-12- 9-9-12 6 Crystal Palace 9-9-12- 9-9-12 6 New Cross 15-15-15-15 4 W Croydon 15-15-15-15 4

For the passenger, the slight unevenness of some branches is not generally as bad as it would seem. Even if one were forced to have a 18-12-18-12 interval (which we now realise we don’t) average waiting time is only 7.8 minutes as opposed to 7.5 minutes for a 15-15-15-15 interval service – an increase of just 18 seconds. In a similar way, the average waiting time for a 9-9-12-9-9-12 interval service is 5.1 minutes whereas a consistent 10-minute interval only reduces the average waiting time slightly to 5 minutes – just 6 seconds better.

Service Pattern (minutes) Mean Waiting Time 18-12-18-12 7.8 min 15-15-15-15 7.5 min 9-9-12-9-9-12 5.1 min 10-10-10-10-10-10 5 min

Not the final deal?

The 20tph ELL proposal should really be seen as a stepping stone to the ultimate aim of running 24tph. This will have to wait until 6tph can be run to West Croydon. Then the intervals can be evened out again with 6tph on each branch. Originally this was planned for 2023, but in today’s financial climate it is hard to see when this will actually happen.

A final curiosity

Something that on first reading is really curious about the proposed train order is the mix of trains. Two trains need to be 4-car for the Barking Riverside Extension. The number required for the ELL is surprisingly large. Analysis of the details given in the paper makes it quite clear that eight will be needed. Assuming one is required to cover maintenance that means seven are required to be in service. With an end-to-end running time and dwell time at one terminus of slightly under an hour for Crystal Palace, West Croydon and Clapham Junction it is easy to see how seven (or maybe even eight) trains are needed. The exact number depends on whether the enhanced routes terminate (at the northern end) at Highbury & Islington or Dalston Junction. It is almost inevitable that the more frequent routes would terminate at the same station otherwise the problem of uneven intervals looms large.

Now the curiosity is this. You might naively suspect that TfL would order eight 5-car Class 710 trains for the ELL, because eight trains are what is required. This won’t work because the Class 710 trains do not have an end gangway and so are not permitted to run in the East London line tunnel. So then you might expect TfL to order eight 5-car Class 710 trains to replace 5-car, dual voltage Class 378 trains from the NLL and WLL combined fleet. But this is not exactly what they propose to do.

The actual plan is to order six 5-car Class 710 trains to replace six trains on the NLL/WLL, which can be transferred to the ELL. Then, for reasons that aren’t explained in this document, one 4-car Class 710 is required to replace a 5-car 750V DC train on the Watford DC service. This would enable a seventh 5-car Class 378 train to be transferred to the ELL. The reason for this is that that this is intended as the continuation of a plan to replace the 5-car Class 378 with 4-car trains Class 710 trains on the Watford DC line and run a 4tph service using 4-car trains rather than a 3tph service using 5-car trains.

This still leaves the ELL short by one train.

Another 4-car unit would be released for use on the same service (Euston DC) by leasing an additional unit to run the Romford to Upminster service. A further two 5-car Class 378 units could then be released to deliver the enhanced service level of 20tph on the ELL

To be clear, the unit released from the Romford to Upminster service would be a new Class 710 already delivered as part of the main order.

Keeping Class 315

What is also curious, and smacks of real financial stringency is the fact that a Class 315 is being retained. It is not explicitly stated but it is quite clear that this is intended for the Romford – Upminster London Overground service in order to release a Class 710 for the Euston DC service. This, in turn, releases a further Class 378 for the East London Line service enhancement.

At present, the Class 315 train is used by TfL Rail and London Overground but in both cases the fleet is due to be scrapped. The London Overground services into Liverpool St would be replaced by the Class 710 trains currently on order as the main part of the contract. It is also presumed that this class of train would be finally scrapped once the new Class 345 fully takes over when TfL Rail’s Liverpool St – Shenfield service becomes part of the Elizabeth line in May 2019.

The problems of maintaining non-homogenous fleets are well-known. At least, for the short term, there should not be a shortage of spares. On top of this, the retained Class 315 will probably be the one in the best condition. Nevertheless, this cannot be seen as a long-term solution.

As part of the Class 315 fleet

More curious still is a reference to other Class 315s being retained. To quote:

One additional Class 315 train would be retained within the broader rolling stock fleet under this option…

As it was believed that the entire Class 315 fleet, currently all used by TfL Rail, was due to be scrapped this seems very strange indeed. Furthermore, the implication is that “the broader rolling stock fleet” refers to the London Overground rolling stock fleet, not the TfL Rail one.

The only plausible explanations so far are that TfL Rail have a plan to delay using 7-car Class 345 on the residual Gidea Park – Liverpool St (High Level) service that will operate in May 2019 when the Elizabeth line opens to Shenfield. Alternatively, that there are plans to run a new self-contained London Overground service to Meridian Water (the replacement station for Angel Road) and do it on the cheap with Class 315 stock.

What the TfL Committee thought of the proposal

With money tight (and perhaps with the memory of Garden Bridge looming), the TfL Board does seem less willing to simply rubber stamp proposals that are put before them. Understandably, board members queried whether it was a good idea to buy trains in advance of them being required just to get them at a cheaper price. It was even suggested that Bombardier would dearly love the order and, if the rolling stock were purchased later, then TfL would be at little or no disadvantage.

Not surprisingly, there was a lack of universal confidence amongst Board members that, if some trains were not immediately required, it would be possible to sub-lease them. It was pointed out to the proposer of this purchase that we are currently an unusual situation. Right now there is a small surplus of electric multiple unit rolling stock around and there may well not be any takers.

Follow the money

The Committee resolved to look at the finances with the public removed from the meeting, as there was confidential information involved. The proposer of this purchase, or more strictly, of a motion to delegate authority to purchase, seemed quite unfazed by this suggesting that he knew that the figures would convince the Committee of the wisdom of going ahead with authorisation.

And so it was. After a discussion behind closed doors, the Committee gave the necessary authority to purchase the trains. One cannot help thinking that the terms available under the original contract (including finance arrangements) made in a more financially confident world, were so much better than anything that could be obtained today. If so, then it is not surprising that the Committee approved the authorisation to order the extra trains.

Consequently, somehow, despite all the current financial stringency, the story of an ever-growing London Overground continues – even if not at the pace envisaged a year ago.

Good news and bad news

Looking at the bigger picture, the good news is that train procurement at TfL has not come to a halt. In fact, in this case, plans have actually been advanced. So there is some money available to spend if the case is good enough. The bad news is that the details of this procurement show just how desperate TfL are to save money whenever possible with a reliance on a Class 315 unit that from a fleet that was expected to be scrapped.

Nonetheless, this is progress in the ongoing quest to make 6tph the regular frequency on the majority of London Overground services. What is more, the services to which this should eventually apply include all London Overground services (with the exception of the Romford – Upminster shuttle) that don’t terminate in central London.

This is no mean achievement, considering that at the time of Dr Beeching any London suburb-to-suburb service was generally regarded as fit only for closure.