Improving Brixton to Nunhead Jct

[brad465]

My impression is the said stretch of railway is congested and full of bottlenecks most of the time, not helped by Southeastern trains often needing to cross between pairs of tracks in the 4 track stretches, while Shepherd's Lane Jct and Nunhead Jct at each end having low speeds on one of the common divergences.

The Overground and Thameslink services appear to work on the basis that, between Peckham Rye and Loughborough Jct/Clapham High street, they normally stay on the same running lines throughout. However Southeastern and freight services have to crossover at least once.

Among ways I think this could be improved; Nunhead Jct should be remodelled to allow trains to/from Lewisham to enter and clear the junction faster (currently 20mph I believe), while trying to maintain the current speed for Catford routed services. If it's possible to reduce the length of or eliminate the 20mph restriction on the non-flyover route from Shepherd's Lane jct to Denmark Hill, then perhaps some SE services would not have to crossover between Peckham Rye and Denmark Hill. This would be most effective with down services considering Brixton station is by the flat jct.

If it was possible to go a bit more extreme, Nunhead could be expanded to 4 platforms, or at least 4 tracks at this point, to allow the possibility of overtaking stoppers (especially in the peak). If the 20/30mph restriction on the down line between Nunhead and Crofton Park has a braking impact over Nunhead Jct, then removing this will also speed up train passage through here.

 

[30907]

The facility to run SE services over the Atlantic Lines, introduced about 40 years ago, introduces conflict, particularly for down trains; however
(1) the multiple track layout out of Victoria gives some flexibility of routing
(2) the junctions used are all medium-speed rather than 20mph, which makes crossing moves less disruptive.
(3) the Atlantics provide a freight route with minimal conflict.

In terms of the improvements you suggest
(1) even if there were space to remodel Brixton/Canterbury Road Junctions for higher speed, it would be enormously expensive as the whole line is on viaduct, and you would be pushed to save 30 seconds' running time.
(2) Nunhead Junction might be worth looking at, but it would require land take, and if there is a 30 speed restriction on the curve beyond the junction towards Crofton Park, the saving would be minimal (again, max 30 seconds for a non-stopping train on the Lewisham route). I am assuming the 30 is because of the curve.
(3) for overtaking purposes, a loop at a station on its own simply delays one train by at least 3 minutes to benefit another; you need 2 consecutive stations on the loop for it to bring real benefit, especially on a fairly low-speed route.
(Headcorn was worth it when expresses passed at 90; Kent House and Newington are hardly used now, but again were on reasonably fast stretches.)

 

[Bald Rick]

Shepherds Lane is linespeed in all directions: 45mph

 

[Taunton]

If we are going to look at new platforms here, surely the one to start with would be at Brixton on the Overground. It seems poor that one of the key urban centres in south London has the line running right through its middle with no station stop. I am aware it would be an interesting engineering challenge to design it up on the higher viaduct, but is surely not impossible.

 

[4-SUB 4732]

You'll need six platforms at Brixton in reality. If you only put them on the Atlantic lines, what happens if SE stuff needs to run via the Catfords? You've now got to miss out a potentially huge interchange. It's going to be a big ask in any event and you might be better off doing something a bit different.

 

[30907]

(2) Nunhead Junction might be worth looking at, but it would require land take, and if there is a 30 speed restriction on the curve beyond the junction towards Crofton Park, the saving would be minimal (again, max 30 seconds for a non-stopping train on the Lewisham route). I am assuming the 30 is because of the curve.

I have now had time to check the NR Sectional Appendix for permitted speeds
1. there is a short section of 20/30 on the Down Catford Loop beyond Nunhead Jn (as mentioned) but otherwise the limit is 50 from Crofton Park, 55 over the junction and 60 towards Peckham Rye. The Lewisham line is 25, but for the small number of trains involved at peak times a major upgrade would be difficult to justify.
2. the only way I can see of improving speeds at Brixton would be to single the line from Brixton Jn to Canterbury Rd Jn and use it as a Down line only as far as possible. You could also then reinstate a platform.
BUT - even with normal working - in the morning peak there is some ECS from Blackfriars which needs to route that way for efficiency.
By singling the line you are imposing additional performance risk.

On Taunton's suggestion about the interchange with LU: having used it recently, it would also need a major rebuild with proper subways as the only link is along the road.

 

[Ianno87]

If we are going to look at new platforms here, surely the one to start with would be at Brixton on the Overground. It seems poor that one of the key urban centres in south London has the line running right through its middle with no station stop. I am aware it would be an interesting engineering challenge to design it up on the higher viaduct, but is surely not impossible.

Not impossible, but probably colossally expensive.

 

[brad465]

I have now had time to check the NR Sectional Appendix for permitted speeds
1. there is a short section of 20/30 on the Down Catford Loop beyond Nunhead Jn (as mentioned) but otherwise the limit is 50 from Crofton Park, 55 over the junction and 60 towards Peckham Rye. The Lewisham line is 25, but for the small number of trains involved at peak times a major upgrade would be difficult to justify.

My impression was the 20/30 restriction had something to do with the embankment. Also is the Sectional appendix still publicly available? I tried to look there ahead of starting this thread for info but old links in this forum no longer work.

 

[frediculous]

In the Kent Route Study, there's a section about adding a third track just on the north side of Nunhead, although no extra platforms

 

[swt_passenger]

My impression was the 20/30 restriction had something to do with the embankment. Also is the Sectional appendix still publicly available? I tried to look there ahead of starting this thread for info but old links in this forum no longer work.

Sectional appendix pdf copies are available here:
https://www.networkrail.co.uk/indus...ators/national-electronic-sectional-appendix/
you need to scroll down beyond the bit about the live version and passwords etc...

 

[brad465]

Sectional appendix pdf copies are available here:
https://www.networkrail.co.uk/indus...ators/national-electronic-sectional-appendix/
you need to scroll down beyond the bit about the live version and passwords etc...

Great, thank you