The Secret Life of Seven Sisters

One of the notable things about the Victoria line is just how busy it is. Unlike other lines (except the trivial Waterloo and City) there are just no quiet stretches. Although Blackhorse Road and Pimlico may be regarded as relatively lightly-used, this is only by Victoria line standards. There are no truly quiet stations on the line. It is quite surprising, therefore, that if you know where to look you can find a platform on the Victoria line that has an eerie silence and an almost sinister lack of people waiting for the next train – for most of the time, at least.

That Platform is at Seven Sisters.

The rather sparse Platform 4

The rather sparse Platform 4

If the mass of quirky underground statistics included one for the blandest platform, then surely platform 4 at Seven Sisters would be it. Note the almost total lack of adverts unlike other platforms. Note also a complete lack of people despite being on the busiest (in terms of most densely used) line – which is probably the reason for the lack of adverts.

The clue for this surprising lack of people is given by one of the very few signs facing a potential waiting passenger.

Well technically they DO...

Well technically they DO…

It’s a statement that, if taken literally, is clearly nonsense. In fact trains depart from this platform about every ten minutes and even more frequently in the peak.

At this point the reader might be forgiven for thinking that there is a competition going on to write the dullest article we can:

“You read A Brief History of Sidings. Don’t miss Seven Sisters Victoria Line station – an architecturally boring station with the blandest platform you ever did see!”

We do hope you will continue reading though for, as far as Underground stations go, Seven Sisters is actually one of the most interesting.

Most people tend to think of Victoria (or possibly Oxford Circus) as the hub of the Victoria line, but in operational terms the really important station is Seven Sisters. Victoria is just an ordinary station – albeit a very busy one – with a couple of sidings that can be used in an emergency. Brixton is a very busy terminus but there is nothing particularly special about it. Seven Sisters is important and different.

Three is the perfect number

Seven Sisters is a rare example of a deep-level tube station with three platforms on one line. Until the Jubilee line opened it, it shared this feature with Baker Street on the Bakerloo line. Since the Jubilee Line Extension opened it has shared this distinction with North Greenwich. North Greenwich is visually distinct from Seven Sisters, however, as it was built as a concrete box and not by deep-bore tunnelling. There are stations with more than three platforms of course – Camden Town, Euston and Kennington on the Northern line all have four, but in each case they are on two distinct branches. Seven Sisters is thus just a little bit special.

The three platforms at Seven Sisters are just one of the features of the Victoria line which reflect the considerable thought that went into the design of the line to give it maximum operational convenience and flexibility. Numerically, the platforms in question are 3, 4 and 5 (the National Rail station on top having claimed the first two ordinal numbers). Platform 3 is the northbound platform and platform 5 is the southbound one. Adjacent to platform 3 and accessible to it by cross-passages is platform 4.

Platform 4 possesses some unusual touches. Although at first glance it looks like an ordinary platform (the previously identified lack of advertising aside), it also features something that originally could not be found on any other Victoria line platform. At the western end (and visible in the photo above) is a pedestrian overbridge cut into circular cross-section of the platform tunnel. This was avoided at other station for aesthetic reasons. With no-one likely to be waiting here on the platform, avoiding it was obviously seen as an unnecessary luxury here.

Note the glare of the red signal located in the tunnel at the west end of the platform. This is a Fixed Red Light which means that trains never depart in this direction.

If you do linger on platform 4, then you will probably be approached by staff who presume that you are lost and need assistance. Indeed this platform must be about the only place on the underground where the staff are actually less likely  to approach and ask you questions if you are holding a camera in your hand.

The tracks at Seven Sisters

The tracks at Seven Sisters

Above is a diagram showing the relevant tracks. The little wings on the lines to and from the depot are simply points designed to derail any train that is heading for the “main line” without authorisation. Thanks to swirlythingy for providing this.

Why does this platform 4 exist?

Firstly it enables trains to terminate there. As can be seen from the diagram, trains can advance to either line to the depot and return from there to platform 5. Because of the intense frequency of the Victoria line it would be impractical to terminate trains at Seven Sisters with just two platforms. This was true at the time the Victoria line was designed, but it is even more true now that there are strict rules that require trains to be checked to ensure there are no passengers still on board. These rules have been slightly relaxed now (but not yet for the Victoria line stock), but it would be particularly undesirable for unauthorised passengers to be allowed to enter the depot. As a result, they would probably still need to be implemented at Seven Sisters.

Terminating trains here has two benefits. Firstly, it cuts down unnecessary running to the terminus at Walthamstow Central on the section of the line that is slightly quieter than the rest of it. Secondly, without it all northbound trains would have to terminate at the two platforms at Walthamstow. Operationally, with the incredibly frequency of trains run, this would be highly undesirable. Indeed the line is currently constrained by the need to terminate all trains at the southern end at Brixton. Terminating all trains at Brixton was not the original intention – as discussed in A Brief History of Sidings – but this is now the case and Brixton is thus reputed to be the busiest underground two platform terminus in the world.

There is another reason for platform 4. That is because the depot is actually located at Northumberland Park, about a mile north-east of Seven Sisters station. This was probably the one inconvenient feature the planners could not avoid. With just one northbound platform it would have been awkward to check the train was empty before going to the depot. So an extra platform with a tunnel leading from the end of the platform to the depot, is an ideal flexible arrangement. The tunnels leading to the depot can thus also double as sidings for trains terminating at Seven Sisters before continuing back to Brixton as described above (although this would obviously block the route either to or from the sidings).

A further consideration is that it is very awkward for staff to get to Northumberland Park depot from Seven Sisters at ground level. Platform 4 makes it possible to provide a staff train. Indeed this is timetabled to run every twenty minutes except during peak periods. This doesn’t mean the platform only deals with three trains an hour. Typically every alternate off-peak train that terminates at Seven Sisters returns to Brixton, and during peak hours one train has scarcely been checked for passengers and departed before the next one is approaching.

Seven Sisters Depot Destination

Staff know that this is a staff train to the depot because of the diamond present

Seven Sisters Normal Destination

This train will wait in the platform for a while before going a short distance into the tunnel and then reversing into platform 5

Staff Halt at Northumberland Park

If you were able to stay on a train to the Depot then this is where you would end up.

Staff trains from the depot run straight into platform 5 and enter passenger service there. The only thing that identifies that a train originated at Northumberland Park Staff Platform is that the outside is clean and still wet from going through the washer on departing from the staff halt.

The question of Northumberland Park

As soon as people get to know of a piece of railway infrastructure in London that does not carry fare-paying passengers, there is the inevitable suggestion that it could be put into use for the public by some means or other. The twin tunnels leading to the depot are no exception and at first sight would seem to be ideal for providing a service to Northumberland Park. In particular this is supported by Tottenham Hotspur football club and their fans. Sadly, such a thing will likely not happen for a number of reasons.

Firstly, there simply isn’t the space in the depot to build a station – even ignoring the fact that the depot is not ideally situated. As an alternative it has, in the past, thus been proposed to build a station alongside the existing mainline railway. There is indeed space, but there are plans to reinstate four tracks here so that is a non-starter too. Current philosophy is also that Underground lines with an intensive service should be kept simple and branches should be avoided if at all possible.

On top of all this, the cost would be well over £50 million – money that could probably be better spent elsewhere. It would not simply be a matter of improving the staff halt and providing safe walking routes, as the depot needs to be a secure place and a publicly accessible station would thus need to be physically separate. Finally, given the desolate location of the depot it is difficult to see much traffic generated other than park and ride except when Tottenham Hotspur themselves play at home.

Resignalling the line

Of operational interest is a recent development to the lines to the depot. Readers will probably be aware that since the withdrawn of the original 67 stock the Victoria line shut on many weekends to commission the new signalling on a section by section basis. Following completion, a new timetable was introduced on 22nd April 2012 to take advantage of the faster trains. By speeding them up a 33 trains per hour (tph) timetable was introduced and replaced the 30tph one that was based on the now-scrapped 67 stock. Amazingly this was done without any publicity and the only indication on the TfL website indicating it had taken place was a minor change to the first and last times to take into account the faster journeys. The date of commencement of these times featured as a small footnote. Assuming we are correct, and that the Victoria line now regularly runs 33tph, then it appears a decision not to publicise has been made, it’s tempting to wonder whether this was to avoid adverse criticism that the Jubilee line can still “only” manage 30tph despite many weekend closures.

Given that the line had been resignalled by the end of April, a few eyebrows were raised at its closure again over the May Bank holiday. This was in fact intended to make both lines to the depot fully bidirectional. We understand that in fact the work was not completed, and we await a future date for this. This will probably involve a future closure but with the Olympics and closure dates normally planned at least six months ahead we do, not expect to see this any time soon.

Making the depot lines bidirectional has a number of advantages. The obvious one is that in the event of one track not being operational it would still be possible to get trains to and from the only depot on the line, but there are less obvious benefits. One line could, for example, be used as a test track (although it is probably a bit late for that). Another is that with the trains becoming busier earlier in the morning, it is becoming quite a challenge to get all the trains in service quickly once the service begins. Having both lines available means that two trains can independently enter service at the same time although this would involve a reversal for one of them on platform. Note that despite the “trains do not depart from this platform” notice, it is perfectly possible for a train to leave platform 4 in service and continue to Tottenham Hale and indeed this currently happens. The necessary crossover tunnel built so that trains from platform 4 can continue towards Tottenham Hale is yet another piece of admirable foresight built into the Victoria line despite the pressure at the time to cut costs.

The tricky issue of automation

Finally, as we also discussed in A Brief History of Sidings, at times of disruption the biggest problem is getting rid of trains. On the Victoria line the best way to do this is to utilise both depot tunnels to send some trains back to the depot simultaneously from both the northbound and the southbound platforms.

Despite being a generally well thought out design there is a surprise – and surely regretted – omission from the track layout in this area. What is missing is a very short link from the west end of platform 4 to join the southbound running line. Such a line would have enabled trains terminating at platform 4 to go directly to Finsbury Park without reversing in the tunnels to the depot. An additional advantage of this, which was not relevant at the time of construction, is that it would remove the need to ensure that all passengers had disembarked. It may have been extreme pressure to cut costs or a desire to ensure that everything was kept simple for passengers with all southbound trains departing from platform 5, but whatever the reason it was one of the few real oversights made during construction. There was no desperate need to commission such a link straightaway, but a failure to put the necessary bare short tunnel in place during construction was a piece of short-term thinking that is now almost impossible to rectify at any reasonable economic cost.

We will finish our short sojourn to Seven Sisters by looking at a quirk it almost had, rather than one it actually does – fully automated services, on entry from them depot at least.

This was an opportunity that presented itself during the stock replacement and resignalling. Trains could have been run automatically without a driver or other supervisory staff between the station and the depot. Despite the fact that it is the station that is the main driver booking-on point and not the depot, this was an option that wasn’t exercised. In part this was likely because it would have pushed the current technology to the limit. It would also have meant a union confrontation for relatively little gain. Mainly, however, it was for a reason that is very familiar across the Underground network – the age of the old rolling stock meant that something needed to be done relatively quickly and there wasn’t really time to investigate some of the more far-reaching ideas. The Public Private Partnership was probably also a factor, is it discouraged risk-taking even when there was much to be gained. Now that the equipment is working reliably and effectively “under guarantee”, the mantra “if it ain’t broke don’t fix it” will almost certain (and arguably rightly) prevail for some time yet.

Mind The Gap at the Seven Sisters

Mind The Gap at Seven Sisters, with thanks to Diamond Geezer

Written by Pedantic of Purley