A Study in Sussex Part 10: South Croydon & BML2


Our journey down the Brighton Line has now got as far as South Croydon. Not only do we look at the station but also at the five track section between East Croydon and South Croydon. There we ask whether it is practical to add a sixth track and, if so, consider whether it would be worth doing. Finally, we take a brief look at BML2’s plans for South Croydon.

The importance of South Croydon – or otherwise

In terms of passenger numbers, South Croydon station is not really that important. Although it is a junction station, no-one would use it to change as it makes far more sense to do so just up the line at East Croydon. Similarly, many potential passengers who could start their rail journey at South Croydon prefer to make their way to East Croydon instead, as it is served by frequent fast trains to central London.

South Croydon station looking south

South Croydon station looking south

Far more significant than the station is the junction just to the south of it. It is here that trains to Oxted (East Grinstead and Uckfield services) join and leave the main line. As such, not only is it an important junction, but also a source of delays – for there is no grade separation. Although not actually at East Croydon, the junction is regarded by Network Rail as part of the East Croydon problem and believes it should not be considered in isolation.

Reference is often made to “East Croydon and the Selhurst triangle” in an attempt to identify the critical area that needs investigating in order to improve the Brighton Main Line. To fully understand the complexity of all this though one also needs to take into account what happens just south of South Croydon station. Effectively the fast Brighton lines, the slow Brighton lines and the Oxted lines are all funnelled into East Croydon. Then there are also fast and slow lines from East Croydon and double track from West Croydon. These need sorting out to get trains to or from the fast or slow lines to London Bridge or Victoria.


SC-1b modified

Development of lines through South Croydon

As with many main lines into London, the section between East Croydon and South Croydon has a history of having tracks added. Unusually, this has resulted in five tracks. This is almost certainly because it was designed first for two and then four tracks and then, when it was realised it was less than ideal and more tracks were desirable, it was only easy to add a single extra track.

Just to the south of the station

Contrasting styles of bridge just south of the station

Until 1984 the fast lines were served by platforms 3 and 4. Platforms 1 and 2 then served the slow tracks to and from Purley. This had the considerable advantage that the trains from Oxted could easily join the fast tracks. Indeed it would have been very awkward for them to join the slow tracks as this would have meant crossing the fast tracks. It was also much more convenient for passengers if the slow lines called at platforms 1 and 2 as access to platform 1 did not involve using the narrow subway. Nowadays it is rare for a train to stop at platforms 1 or 2.

1984 onwards


Current layout at South Croydon

From 1984 onwards the lines were swapped with the fast lines being on the western side with the lines at East Croydon being swapped a couple of years later. The opportunity was taken to organise the remaining three lines in a much better way with a reversible middle track (track 4) between East and South Croydon. The junction was made much more complicated to allow for flexibility in use.

The disadvantage with the arrangement from 1984 at South Croydon was that the trains to and from Oxted, which are fast north of East Croydon (and rarely call at South Croydon), had to use the slow lines. As we saw in our look at East Croydon this is far from ideal. Even if the current proposals for East Croydon get implemented they will still mean conflicting movements for fast trains from Victoria that continue via Oxted. The latest published East Croydon scheme does, however, mean that it is only these services that will be a problem north of East Croydon. This means that radical grade separation at South Croydon, possibly involving the fast lines, if it ever had been considered and believed possible, will be much less of an issue if the East Croydon scheme gets the go-ahead. Indeed an emerging theme of re-organising East Croydon is that, if you sort things out properly north of East Croydon, there is much less that needs doing south of it.

The future impact of changes at East Croydon

Things have moved on a bit since the final version of the Sussex Route Study was published. Network Rail now think it may be possible to almost totally eliminate delays due to conflict in a northbound direction north of East Croydon. If this is true then this would be a real game changer as far as the morning peak flows at South Croydon are concerned. A slow train from Purley could travel via platform 3 at South Croydon to the new platform 5 at East Croydon and beyond. Independently, another train from the Oxted lines could travel via platform 4 at South Croydon to the new platform 6 at East Croydon and beyond. This would be much better than the present situation, as both trains currently have to call at platform 4 at East Croydon, which inevitably delays one of them.

Providing a reliable service as described would mean that up trains would take priority over down trains at South Croydon Junction, but that should not be too much of a problem in the morning peak. In any case, down trains to Oxted and beyond travelling via platform 5 at South Croydon would be unaffected by the ups. The only trains that may be delayed would be the down slow trains travelling via Purley and calling at Purley. If they do not call at Purley then they can travel via the fast lines and avoid South Croydon Junction altogether. Even if they do need to call at Purley then, providing they are not also calling at South Croydon and Purley Oaks, there will be the alternative of switching from fast to slow tracks just north of Purley – though this does mean crossing the up slow.

If Network Rail’s current ongoing analysis of future train movements is correct and their East Croydon proposals come to fruition then in the morning peak it should be possible to run a much more intensive peak period service than today without too many issues. There are also a couple of tricks they could employ to minimise the problem of down services in the morning peak. One is to slightly delay the return service from London so it is at not quite the same intensive frequency, although this has its limitations. The other is to stable some of the trains in the depot at Selhurst after their long distance inward journey to London, so that they do not impede on critical Selhurst/East Croydon/South Croydon junctions.

Because the southbound configuration over the whole Selhurst/East Croydon/South Croydon area will not be as flexible and conflict-free as the northbound service, this suggests a more intensive service could be operated in the morning peak than the evening peak. This should not cause too much of a problem as the evening peak is generally less intensive, but longer-lasting, than the morning one. Such a situation would not be unique. Southeastern metro services run on a 20 minute cycle in the morning peak and a 22 minute cycle in the evening.

East Croydon to South Croydon

We have briefly mentioned this section of track before in a previous article. It is critical because if anything goes wrong here then there is no realistic diversionary route of any kind – and it is not in the sort of area where you want to be running replacement bus services. The two Croydon stations on the Brighton Main Line (South and East) are only about a mile apart along a straight section of track, but a suitable road route would be longer and journey times unpredictable.

Indeed, perhaps tellingly, East Croydon to South Croydon is probably the only section of track along the Brighton Main Line that never seems to have a planned closure for engineering works. Instead there are complicated engineering arrangements to keep some tracks open whilst working on others. A fairly recent innovation has also been to try and make the fast and slow lines completely independent of each other (as regards power supply etc.) to minimise the possibility of all the lines being affected by a single failure.

East Croydon to South Croydon might not close for planned works but there is always the possibility of an unexpected event that cannot be mitigated against – most notably the Thames Water leak of August 2011 that shut the line and caused considerable problems. More recently and more implausibly it nearly got shut because of a deer that was believed to have been on a steep railway embankment near East Croydon station.

A five track railway

Number of tracks

Diagram showing number of tracks from Windmill Bridge to South Croydon

Currently there are six tracks just south of East Croydon but these reduce to five after a short distance to the south of the station. There remain five tracks all the way through South Croydon station. There the line to Oxted (two tracks) diverges off whilst four tracks continue towards Purley.

Deep Cutting South Croydon - East Croydon

The deep cutting between East Croydon and South Croydon looking north from South Croydon

It is hardly surprising that it is often suggested that six tracking from East Croydon would be a good idea. Unfortunately the line is in a deep cutting for most of the distance between these stations so that would not be cheap to do. Worse still there are already retaining walls on both sides. It’s also the case that having “only” five tracks is not currently a major problem and there are far more important restrictions on capacity that need addressing first – notably East Croydon.

Just north of South Croydon looking north

Just north of South Croydon station looking north

Not surprisingly there were responses to the Sussex Rail Study suggesting an additional track through South Croydon and even beyond to Purley. More surprisingly, rather than being dismissive, the Network Rail response was:

The final approaches to East Croydon station see the Down Slow-side in a high walled cutting whilst structures can be found close to the line on the opposite side. The existing proposals in the Route Study would allow some more services to operate through this section without additional tracks – though it is noted and agreed that in the long term either a signalling technology solution or an additional track could be required on this section.

Not stated, but fairly obviously, there really is not much point in having six tracks north of South Croydon if you do not have six tracks through South Croydon station itself. Having got that far south, the junction to Oxted is almost on top of you so the tracks would have to continue to it.

On the presumption that there is no point in providing an additional track for the fast services, as there isn’t a problem here and it would achieve nothing, if there were to be six tracks then it would make sense for there to be two up slow, two down slow and two fast lines. The slow lines would use the existing island platforms and the up fast platform, now rarely used, could be sacrificed if necessary.

Train passing platform 1

Fast train passing platform 1

It looks as if it would be fairly simple to demolish the up fast platform to provide a new up fast line. The current up fast could become the down fast and that would leave the two island platforms for the four slow lines. The station buildings would probably need to be rebuilt, but it is arguably due a comprehensive rebuild anyway as it has multiple deficiencies at present. There is plenty of space available in the car park, which uses the space vacated by the former carriage sidings.

Even without grade separation at South Croydon Junction or an extra track northwards to East Croydon, four platforms for slow lines could potentially improve the situation at South Croydon Junction. A slow train waiting to continue southwards towards Purley could sit in the current platform 4 whilst a following train to Oxted and beyond could pass it via the current platform 5.

Note that Network Rail has no plans for six tracks through South Croydon and its positive response in the route study to the suggestion was really a case of keeping their options open, rather than any plans to do it. They are convinced that considerable improvements can be made at South Croydon through a limited amount of resignalling and that is currently what they intend to do.

Six tracking all the way between South Croydon and East Croydon would be a nice-to-have, but it would involve major engineering due to the steep embankments and is probably even less likely to happen than six tracking at South Croydon station itself. Theoretically it does seem possible, however. There is a good reason for establishing that is the case, to which we will come later.

The alternative to six tracks

It is likely that Network Rail don’t think six tracks will be necessary. With an extra slow platform at East Croydon it could terminate more trains there. The three slow tracks between East and South Croydon, together with a re-organised East Croydon could work very effectively.

Below is an illustration of how services could be organised in the peaks with the minimum of conflict at South Croydon.

SC3-3 peaks

Possible scenario for peak working on the assumption work proposed at East Croydon goes ahead.

South Croydon station

South Croydon is not the busiest of stations but it is well used in peak hours. This can be accounted for by the fact that the off-peak service to central London isn’t that good (2tph slow to Victoria, 2tph slow to London Bridge) and peak period figures are boosted by Whitgift School being nearby. Outside peak hours, if not starting one’s journey very close to the station, there is a considerable incentive to catch a bus, or possibly walk, to East Croydon instead.

Narrow Subway

Narrow subway

The station itself is also hardly inviting. The fast platforms (1 & 2) rarely see a train stopping there as, amongst other things, this would considerably reduce the capacity of the fast lines. Meanwhile the remaining three platforms are accessed by a very narrow subway. The platforms themselves are also low, meaning a large step up is needed to get to the train. Those trains are also restricted to 8-car length, although some peak period 10-car and 12-car trains are timetabled to call there and use selective door operation (SDO).

In the off-peak period the three “slow” platforms have to accommodate the four stopping trains an hour in each direction. They also have the trains to and from East Grinstead and Uckfield passing through and there are various trains that run fast between East Croydon and Purley. There is also an hourly train from Milton Keynes via Kensington Olympia that terminates there.

Platform mirror with SDO notice

Mirror at south end of platform 5 with SDO notice

South Croydon – Milton Keynes

One must not be misled into thinking that, in general, the train from Milton Keynes terminates at South Croydon for any reason related to convenience to passengers. It is simply a case of not wishing to block the platforms at East Croydon and terminating at South Croydon was decreed to be the most practical way to achieved this, especially when taking into account the need to avoid more rolling stock being required for the East Croydon – Milton Keynes service than was essential. Terminating at South Croydon also has the benefit of not adding to the conflicting moves at South Croydon Junction.

Crossover for Milton Keynes - South Croydon terminators

On the left of the picture is the crossover installed for Milton Keynes terminators

As a result of the decision to terminate services from Milton Keynes at South Croydon, the necessary terminating facilities (a crossover and revised signalling) were installed a few years ago. In the late morning peak one of the trains from Milton Keynes is well used at its southern end by pupils going to Whitgift School – as Southern Railway found to their cost earlier this year when they, for a very short period, terminated it at East Croydon to assist with reliability of the problematic Southern timetable. Its continuation to South Croydon was very quickly reinstated.

The difficulties of any South Croydon Junction improvements

As already established, the junction immediately to the south of the station is South Croydon Junction. Here trains for East Grinstead (4tph peak/ 2tph off-peak) and Uckfield (2tph peak/ 1tph off-peak) join and leave the Brighton Main Line. It would be ideal if these joined the fast lines at South Croydon but they don’t, because they are literally the wrong side of the tracks. If East Croydon gets rebuilt this will be less of an issue, as up trains on the slow lines will then have a conflict-free route to both London Bridge and Victoria. In the down direction the route from London Bridge will be almost conflict-free and it will only be in the down direction from Victoria that things will really be less than ideal.

Joining the Brighton Main Line slow lines from Oxted in the peak periods is not too bad at present, as four of the six trains per hour in each direction start from or continue to London Bridge. Whilst the route to London Bridge (fast) is not conflict free, the route from London Bridge is and, if the tracks around East Croydon get rebuilt, the route will be conflict-free in both directions. Based on the current timetable, only two of the trains will be routed to and from Victoria on the fast lines.

Public footbridge at north end of platforms

Public footbridge at north end of platforms

The space available for grade separation at South Croydon Junction is extremely limited. The two lines south of the station divide immediately, a road bridge is crossed and the routes diverge quite rapidly. A public footbridge that crosses the station prevents grade separation to the north. The road below the bridge at the south of the station rules out a diveunder so the only possible way to grade separate the junction would be through the use of a flyover. Apart from the technical difficulties it would be difficult to see this being acceptable in such a suburban area.

Railway bridge over Croham Road

Bridge taking railway over Croham Road

South Croydon Gateway

As many people know BML2 is a proposed suggestion, not endorsed by Network Rail, to use the Uckfield Line, the disused line from Selsdon to Coombe Road, the existing tramlink line from Coombe Road to Elmers End, the current Hayes Line and a new tunnel to create an alternative route to the Brighton Main Line, to Canary Wharf and Stratford and onward to Stansted.

The attitude of transport professionals to BM2 so far has generally been to try and avoid mentioning it in polite (or particularly excitable) company. The consensus has seemed to be that it’s a distraction that would be unbelievably expensive and disruptive and they thus hoped it would go away and be forgotten about. They have been unsuccessful in this quest.

In the early days of BML2 proposals one of the biggest objections was that it avoided all the places that people actually wanted to go to – in particular East Croydon. To counter that the BML2 supporters have proposed a Croydon Gateway station just to the south of the existing South Croydon Station. This seems to have become an essential ingredient of the scheme.

The idea is somewhat mindblowing. The proposal can be found on their website at the bottom of the relevant page. If it ever gets as far as being independently costed it would be interesting to see how it compares with the East Croydon scheme. The idea is that trains from either Brighton or Lewes via Oxted can continue to either London via East Croydon or Canary Wharf and Stratford via the Hayes Line route.

To quote the website:

[T]here will need to be a cross-connection to enable BML trains to cross over onto BML2 and reach Canary Wharf. East Croydon deals with huge amounts of people switching trains and would benefit by having a far larger and purpose-built interchange station at this location currently occupied by light industrial units. It might well be desirable to amalgamate Sanderstead, Purley Oaks and South Croydon stations into Croydon Gateway which would obviously be connected to Tramlink.

One of the problems is that the idea has not been costed and clearly also relies on other parts of the scheme being feasible – parts which haven’t been established and are clearly not costed either. Another problem is the presumption that the service would be willingly used, with no research to establish what demand there would be so far apparent. In other words would “huge amounts [sic] of people” really be willing to change trains at South Croydon Gateway?

BML2 in general

As far as BML2 in general – and South Croydon Gateway in particular – go, it is safe to say that the general consensus at LR Towers is they seem to be rather large leaps of faith. Unfortunately, like women in lakes distributing swords, this is not a sound basis for governing and making decisions. This, of course, doesn’t mean it is definitely a bad idea, just that there is currently no real evidence for it being a good one. On that basis it is hard to see why it is given more credence than any of the many other similar blue-sky schemes regularly suggested by interest groups and others.

The BML2 argument seems to rely on many presumptions that are, at the very least, disputable. It is perceived by its supporters as not only a solution to a problem but the best solution. For example, it presumed there is a requirement for a tunnel from south London to Canary Wharf and that the BML2 solution is the best way to provide it.

Sauce for the goose

One common thread in all the BML2 literature seems to be that the Brighton Main Line is full up and the situation cannot be rectified. In fact, as the evidence seen so far in this series has shown, there is an awful lot of extra capacity that can be made available – almost certainly at a fraction of the cost. If a sixth track were to be added between East Croydon and South Croydon, as indicated is possible, then there would appear to be nothing to prevent extra trains from the Uckfield Line going via East Croydon and onward to New Cross Gate. By allowing a two minute interval on the fast line to London Bridge north of East Croydon you should be able to get in an extra 6tph.

BML2 already proposes a tunnel from Lewisham to Canary Wharf. If instead you had an equivalent tunnel from New Cross Gate to Canary Wharf you could achieve the same objective without having to try and reinstate a disused railway, displace a well used dedicated tram route, attempt to have frequent trams and trains sharing a section of two track railway formation and interwork with either the Hayes rail or even Underground service.

This is not to suggest that there should be six tracking between South and East Croydon. Nor that a tunnel should be built between New Cross Gate and Canary Wharf. It is merely intended to demonstrate that, without commenting on the BML2 proposal south of Uckfield, the BML2 proposals within the GLA area seem somewhat over the top. The fact is that if a route from Uckfield to Canary Wharf were that desirable an objective, it probably could be achieved by much cheaper means. Most of the work at East Croydon would be necessary anyway regardless of whether any aspect of BML2 came to fruition or not.

East Croydon – the problem or the solution?

BML2 claims that East Croydon is “a bottleneck and a significant barrier to growth”. The most recent two parts of this series help show that, while this is currently true, there is no reason why East Croydon need be a bottleneck in future. Far from being a barrier to growth, it is seen locally as a potential catalyst for it. Whatever the merits of BML2 may be, avoiding East Croydon in the future because it is a bottleneck today seems an extremely dubious basis for the proposals made.

Next time we will probably look in detail at the lines to East Grinstead and Uckfield, including a reference to the idea of reinstating the old line from Uckfield to Lewes. However, this will be largely limited to how this and other potential enhancements impact on London’s rail services.

With thanks to ngh for the diagrams of South Croydon

Written by Pedantic of Purley