South Croydon Crossovers

[Deepgreen]

A query about the use of the two crossovers at South Croydon, one to the north of the station, the other just south, both from down Oxted to down BML slow. The northern crossover has a gentler geometry than the southern one, and I would therefore assume its speed restriction is higher.

However, in the many years of commuting on the route, I cannot recall a single occasion when my train has used the 'faster' crossover, even when running late and the ability to recover even a small amount of time would be useful, plus the ability to clear the site more quickly (including the flat junction with the Oxted route. Assuming also that it is passed for passenger moves, why is it never used as I've described?

 

[RichJF]

When I used to commute to London (2012-March 2016) I recall once being on a Thameslink train to Redhill that used the crossover north of South Croydon to bypass a slower Horsham that was held in Platform 5. That was 2015 sometime.

The southern crossover I distinctly remember being used when my London Bridge train was terminated at East Croydon & travelled up the reversible from South Croydon to East Croydon platform 5.

Interesting to note these were BOTH in times of disruption so I assume it's more a case of only if necessary.

 

[Deepgreen]

When I used to commute to London (2012-March 2016) I recall once being on a Thameslink train to Redhill that used the crossover north of South Croydon to bypass a slower Horsham that was held in Platform 5. That was 2015 sometime.

The southern crossover I distinctly remember being used when my London Bridge train was terminated at East Croydon & travelled up the reversible from South Croydon to East Croydon platform 5.

Interesting to note these were BOTH in times of disruption so I assume it's more a case of only if necessary.

Indeed, but I wonder WHY only if necessary as it would seem to be a better route choice unless another train is already in the platform (from either direction), which in my experience is frequently not the case when we are passing.

 

[Bald Rick]

The north one is 40, the south one 20.

What follows is conjecture, and our resident expert at Three Bridges ASC may provide a different explanation. However, the north one will have approach control on it that limits its effectiveness, and may cause restrictive aspects at East Croydon for a train using it. This would also slow the arrival and departure of a following train from E Croydon.

The south one will have approach control too, but I suspect has less of an impact on E Croydon being one signal section further on. Indeed there will be no impact on the train itself if it calls at S Croydon.

 

[tsr]

Whilst not the correspondent from Three Bridges (well, very rarely!), from recent practical experience I can confirm that it is by no means significantly quicker to use that crossover, as per the above. In addition, to do so adds more conflict with the Slow Reversible Line through South Croydon Platform 4 - you have to cross between lines both to the North of the station and again at South Croydon Junction, rather than just the single all-encompassing conflicting move at the latter junction.

The Slow Reversible route can also be used in both peaks to queue up slow-moving passenger trains alongside the Up Slow on approach to East Croydon. To use the crossover North of South Croydon would reduce the effectiveness of this, as it would reduce the number of signal sections able to be occupied (or needed for overlap) due to slow moving (not necessarily stopped) trains moving towards London.

To eliminate using either crossover, a number of passenger services during the day, in addition to freight trains, do head South from East Croydon Platform 5, down the Slow Reversible and straight onto the Down Slow. This particularly includes many trains via Redhill between the peaks, such as Horsham stoppers.

I suspect there may also be a small legacy here from the times when South Croydon - Milton Keynes Ctl services reversed at South Croydon Platform 4, which would have led to Platform 5 being used on a regular basis to avoid this manoeuvre. Obviously this is no longer a consideration at most times of the day, but I seem to remember in the very back of my mind that timings were slightly adjusted for services maintaining a route on the Down Slow via the slower crossover to the South of South Croydon station, in recognition of the reduced speed. It may be that these timings are simply now taken advantage of.

The crossover is used primarily for movements such as the following:
- Preparing for the turning back of stock which would be unable to do so at East Croydon because they had used Platform 6; ECR Platform 6 is permitted for detraining and locking out services, but all stock must in any case proceed to South Croydon Platform 4, or Purley, to turn back anyway.
- Allowing trains to be brought into South Croydon side by side for transferring passengers or crew between them for routes via Oxted, where trains were not sequenced correctly to do so at East Croydon.
- As has been stated above, for fast services to overtake slow ones if insufficient platform lines were available at East Croydon (as an example, sometimes done by GX services on Sundays when the Fast Lines are closed, either as a service recovery or timetabled measure).

 

[Sunset route]

The approach control on the route T131 to T135 signals via 1626 points (the northern set) is so restrictive that it makes using that route in preference to T137 to T143 via 1629 & 1630 points (the southern end) totally useless even though the points (1626) are 20mph faster. It only good for a get out of jail free card when things have gone wrong. It was paid for by the ELL project and even though I attended meetings with then, I never really understood the logic of providing it, especially and it ruined the flexibility of South Croydon interlocking.

 

[Deepgreen]

Thanks for the array of replies. It does seem a nonsense to have a crossover with double the speed limit of an adjacent one, but effectively be strongly dissuaded from using it for the reasons stated. Incidentally, what was the link between the ELL extension (to West Croydon) and the crossover at South Croydon, when East Croydon isn't even served by LO, even, as far as I know, in times of disruption?

 

[Bald Rick]

Thanks for the array of replies. It does seem a nonsense to have a crossover with double the speed limit of an adjacent one, but effectively be strongly dissuaded from using it for the reasons stated. Incidentally, what was the link between the ELL extension (to West Croydon) and the crossover at South Croydon, when East Croydon isn't even served by LO, even, as far as I know, in times of disruption?

Basically, it was that to create the capacity at W Croydon for the LO services, the suburban TT had to be reshuffled, causing some additional trains to head towards E Croydon. But they couldn't terminate there due to the (then) proposed TT, so S Croydon was the next spot. For a while the MK train terminated there.

To be fair, I couldn't understand it either, but by the time I got to that part of the world it was too late to stop it.

 

[Sunset route]

Basically, it was that to create the capacity at W Croydon for the LO services, the suburban TT had to be reshuffled, causing some additional trains to head towards E Croydon. But they couldn't terminate there due to the (then) proposed TT, so S Croydon was the next spot. For a while the MK train terminated there.

To be fair, I couldn't understand it either, but by the time I got to that part of the world it was too late to stop it.

Even though the Milton Keynes used platform 4 at South Croydon, they near enough exclusively used the slow reversible line in both directions from East Croydon and didn't even use the new points. The most the new points get used is when the Wallingtons are blocked and you get the Epsom/Epsom Downs 2Rxx diverted to South Croydon and the Sutton 2Rxx diverted to East Croydon.