Fantasy - Deconflicting services at Herne Hill

If the Thameslink service to the Sutton Loop were terminated at Blackfriars, then the bottlenecks on increasing service frequency would be crossing over the Chatham Main Line at Herne Hill, then the single platform at Wimbledon, then the at-grade crossover at Streatham South Junction. Services on the Chatham Main Line and the Catford Loop are constrained by needing to provide both express and stopping services on two lines which both have stations - so neither branch can have a frequent service of any kind.

But what if the services didn't cross over at Herne Hill?

Then, the Sutton Loop trains would go directly to Victoria, and the Chatham Main Line trains would go to Blackfriars. This could provide a frequent commuter service between Bromley and Blackfriars, with branches to Orpington and Swanley. The Sutton Loop services could increase from their current 2 TPH to at least 12 TPH, provided the other bottlenecks are addressed.

Direct services to Victoria from the southeast of London could be retained by withdrawing stopping services on the Catford Loop and using that capacity for the express services instead. Using one branch for express services and another branch for stopping services can accommodate much higher frequencies overall. I understand that this would leave many passengers without a train service to their local station, but the Mid-Kent Line can support them instead - in particular, the Bakerloo Line extension to Hayes could support the redirected passenger flow.

What do you think? What other infrastructure interventions would be needed to make this plan work?

Well before Thameslink took over the Sutton loop line. There was a train service that ran from London Victoria via Carshalton Beeches, and the same service ran on the Sutton loop line via Wimbledon to London Bridge, which ran to Haydon's Road, Tooting, Streatham, and going to London Bridge via Tulse Hill. Could the Sutton Loop line go direct to London Victoria? Possibly, but I don't think that it can be achieved.

I went through this recently on another discussion. The Sutton loop will only be 2tph because of the at grade junctions at Streatham South and Sutton and the single platform at Wimbledon.

Here it is again:


The key feature of the Sutton loop is that it takes 45 minutes to go from Streatham South Junction round the loop and back to Streatham South Junction. This enables the 2tph timetable to be built on parallel moves at Streatham South Junction and Sutton.

At xx00/xx30 the trains going on and off of the Carshalton side of the loop have parallel moves at Streatham South Junction
At xx15/xx45 the trains going on and off of the Wimbledon side of the loop have parallel moves at Streatham South Junction
At xx15/xx45 clockwise and anticlockwise trains also do a parallel move at the west end of Sutton station going to and from Wimbledon
Furthermore, trains are almost evenly spaced going through the single track at Wimbledon.

With 4tph the parallel moves at Streatham South Junction can only be maintained by accelerating trains to go round the loop in 37 minutes, or retarding them to take 52 minutes. With a 45 minute running time and 4tph there will always be conflicting moves at Streatham South Junction for trains running anti-clockwise round the loop. Furthermore, it becomes impossible to space 8tph through the single platform at Wimbledon.

What is your proposal for where the Luton/St Alban's trains end up after their arrival in London? Where do they terminate and turn around, thus taking up a platform and requiring driver changeover facilities?

squingo44 said:

Direct services to Victoria from the southeast of London could be retained by withdrawing stopping services on the Catford Loop and using that capacity for the express services instead. Using one branch for express services and another branch for stopping services can accommodate much higher frequencies overall. I understand that this would leave many passengers without a train service to their local station, but the Mid-Kent Line can support them instead - in particular, the Bakerloo Line extension to Hayes could support the redirected passenger flow.

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My fantasy in this part of the world is to extend the Victoria Line all the way to at least Bromley South, with stations built below ground for every station above, and all the above ground stations that are not existing interchanges closed. This would both free up mainline capacity and in turn alleviate the Herne Hill bottleneck.

Magdalia said:

I went through this recently on another discussion. The Sutton loop will only be 2tph because of the at grade junctions at Streatham South and Sutton and the single platform at Wimbledon.

Here it is again:


The key feature of the Sutton loop is that it takes 45 minutes to go from Streatham South Junction round the loop and back to Streatham South Junction. This enables the 2tph timetable to be built on parallel moves at Streatham South Junction and Sutton.

At xx00/xx30 the trains going on and off of the Carshalton side of the loop have parallel moves at Streatham South Junction
At xx15/xx45 the trains going on and off of the Wimbledon side of the loop have parallel moves at Streatham South Junction
At xx15/xx45 clockwise and anticlockwise trains also do a parallel move at the west end of Sutton station going to and from Wimbledon
Furthermore, trains are almost evenly spaced going through the single track at Wimbledon.

With 4tph the parallel moves at Streatham South Junction can only be maintained by accelerating trains to go round the loop in 37 minutes, or retarding them to take 52 minutes. With a 45 minute running time and 4tph there will always be conflicting moves at Streatham South Junction for trains running anti-clockwise round the loop. Furthermore, it becomes impossible to space 8tph through the single platform at Wimbledon.

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Which is why my proposal includes removing those two bottlenecks as well

== Doublepost prevention - post automatically merged: 4 Jun 2026 ==

flitwickbeds said:

What is your proposal for where the Luton/St Alban's trains end up after their arrival in London? Where do they terminate and turn around, thus taking up a platform and requiring driver changeover facilities?

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That’s fairly simple, they’d run additional Thameslink services down the Brighton Main Line. If you don’t want to make the infrastructure interventions necessary to add capacity for additional long distance services, they can take over the slow line paths to East Croydon that would otherwise terminate at London Bridge.

== Doublepost prevention - post automatically merged: 4 Jun 2026 ==

brad465 said:

My fantasy in this part of the world is to extend the Victoria Line all the way to at least Bromley South, with stations built below ground for every station above, and all the above ground stations that are not existing interchanges closed. This would both free up mainline capacity and in turn alleviate the Herne Hill bottleneck.

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I agree, that would be a great idea! The only problem is that it wouldn’t allow metro frequency services to run on the Sutton Loop, due to not eliminating the conflicting crossovers at Herne Hill.

All this talk of extending the Victoria line - is there actually room for any more passengers on the bit we already have? Just curious.

I'd like to see the Sutton loop service improved, but wonder if that could be achieved by better staffing/diagramming to improve reliability, rather than changing the destination. More tph would be great but right now it seems every time I look at the CIS between Sutton and Mitcham Eastfields from my comfortable, reliable Southern train it's just cancellation after cancellation of Thameslink.

devon_belle said:

All this talk of extending the Victoria line - is there actually room for any more passengers on the bit we already have? Just curious.

I'd like to see the Sutton loop service improved, but wonder if that could be achieved by better staffing/diagramming to improve reliability, rather than changing the destination. More tph would be great but right now it seems every time I look at the CIS between Sutton and Mitcham Eastfields from my comfortable, reliable Southern train it's just cancellation after cancellation of Thameslink.

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The Victoria line is extremely busy at the moment; most proposals to extend it implicitly rely on other infrastructure projects, like Crossrail 2, to relieve pressure on the line and open up space.

Changing the destination of the Sutton Loop would improve the reliability of the service, not just the capacity. At the moment, delays and cancellations anywhere in the rest of the Thameslink network can propagate to the Sutton loop; disconnecting it would remove the source of instability.

Fundamentally, there’s an at-grade crossover north and south of Herne Hill which reduces the capacity of the lines through the station. You’re not going to be able to get around that without changing the destinations or building a grade separated junction, which Network Rail have said they don’t consider good value for money.

squingo44 said:

But what if the services didn't cross over at Herne Hill?

Then, the Sutton Loop trains would go directly to Victoria, and the Chatham Main Line trains would go to Blackfriars.

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Not 100% following this. How are they getting to Victoria? There'd still be conflicting moves at Herne Hill unless you sent them via Streatham North Junction. But who in their right mind would board a Victoria via Balham service at Wimbledon/Haydon's Road/Tooting when there are far more efficient ways of getting there?

To the OP - do you mean remodelling Herne Hill, such that West Dulwich is locked to Blackfriars and Tulse Hill is locked to Victoria, and that the two systems would operate independently through Herne Hill?

devon_belle said:

All this talk of extending the Victoria line - is there actually room for any more passengers on the bit we already have? Just curious.

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It is often thought that many of the users of the Victoria Line at Brixton head there by bus from the adjoining areas, so an underground extension may spread that demand across different stations.

This seems to cause an an awful lot of inconvenience for very little gain. If you were set on alleviating the Herne Hill divert the Sutton Loop Trains to London Bridge after Tulse Hill. Avoids Herne Hill and doesn't negatively impact change destination for all existing Local/ Mainline Chatham line users or depriving those on the Catford Loop a service.

You then link St Albans with existing Sevenoaks/ Orpington lines all day, with Welwyn peak extras going to Beckenham J.

Sutton Loop line users would get to change at London Bridge Existing for Thameslinkatford Loop Line to anywhere.

Might have to divert LBG - Beckenham J via Crystal Palace LBG - E Croydon J via Norbury in that situation, giving 4tph Vic - East Croydon via Selhurst perhaps?

Not that I'd be pushing for any of this was I a user of the loop

Existing Freight ?

squingo44 said:

Which is why my proposal includes removing those two bottlenecks as well

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Given that Streatham South junction is in a residential area I think there is zero chance of grade separation there. There is also no prospect of grade separation at Sutton. The second platform at Wimbledon was given up for the tram so that's another bottleneck difficult to remove.

Magdalia said:

I went through this recently on another discussion. The Sutton loop will only be 2tph because of the at grade junctions at Streatham South and Sutton and the single platform at Wimbledon.

Here it is again:


The key feature of the Sutton loop is that it takes 45 minutes to go from Streatham South Junction round the loop and back to Streatham South Junction. This enables the 2tph timetable to be built on parallel moves at Streatham South Junction and Sutton.

At xx00/xx30 the trains going on and off of the Carshalton side of the loop have parallel moves at Streatham South Junction
At xx15/xx45 the trains going on and off of the Wimbledon side of the loop have parallel moves at Streatham South Junction
At xx15/xx45 clockwise and anticlockwise trains also do a parallel move at the west end of Sutton station going to and from Wimbledon
Furthermore, trains are almost evenly spaced going through the single track at Wimbledon.

With 4tph the parallel moves at Streatham South Junction can only be maintained by accelerating trains to go round the loop in 37 minutes, or retarding them to take 52 minutes. With a 45 minute running time and 4tph there will always be conflicting moves at Streatham South Junction for trains running anti-clockwise round the loop. Furthermore, it becomes impossible to space 8tph through the single platform at Wimbledon.

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It is possible to timetable 8tph between Blackfriars and Streatham and 4tph each way around the Sutton loop, however it would have to be spaced at 22-8-22-8 minute intervals around the loop for the reasons you mention.

If the Sevenoaks services were permanently sent through the core, the timetable is pretty much already set up for 8tph to run between Blackfriars and Tulse Hill at evenly spaced 7-8 minute intervals (4tph through the core as now and 4tph into the Blackfriars bays), as the paths in each direction at Herne Hill are exactly 7-8 minutes apart, so doubling the service would create parallel moves at Herne Hill and have no impact on Southeastern services into Victoria. While running unevenly spaced intervals around the loop isn't particularly worth it, how about running a 2tph Blackfriars to East Croydon (or West Croydon if necessary) via Herne Hill, Streatham and Norbury service? Such a service could either run in addition to, or in replacement of the London Bridge to East Croydon via Peckham Rye and Norbury service (if it was in replacement, the service via Peckham would be diverted via West Norwood).

Magdalia said:

Given that Streatham South junction is in a residential area I think there is zero chance of grade separation there. There is also no prospect of grade separation at Sutton. The second platform at Wimbledon was given up for the tram so that's another bottleneck difficult to remove.

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Sending the tram through the main part of Wimbledon station is kind of a silly move long-term. I can understand why it was initially built that way (it was taking over a heavy rail route) but you lose one of the key advantages of trams by keeping it that way. If you could divert it onto the streets in Wimbledon town centre (along with associated public realm improvements) you'd not only free up that platform for Thameslink, but also boost ridership on the Wimbledon branch of the tram system.

61653 HTAFC said:

Sending the tram through the main part of Wimbledon station is kind of a silly move long-term. I can understand why it was initially built that way (it was taking over a heavy rail route) but you lose one of the key advantages of trams by keeping it that way. If you could divert it onto the streets in Wimbledon town centre (along with associated public realm improvements) you'd not only free up that platform for Thameslink, but also boost ridership on the Wimbledon branch of the tram system.

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Perhaps a tram station could be built on the curve leading to Wimbledon station; there seems to be sufficient space at the north-east end of the old Wimbledon down yard to build one. Then the former tram platform in the station could be used for services to Sutton. The main problem I foresee is getting tram passengers across to the station; there is a large office block in the way.

I disagree that having the trams terminate at the main station was a mistake. It makes for easier interchange as well

PGAT said:

I disagree that having the trams terminate at the main station was a mistake. It makes for easier interchange as well

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Overall it works, but there are some oddities. In TfL terms the tram is effectively a bus mode. Yet you have touch into a rail environment to then touch on the tram reader to exit the rail environment to make sure you are only charged the 'bus' fare.

NCT said:

To the OP - do you mean remodelling Herne Hill, such that West Dulwich is locked to Blackfriars and Tulse Hill is locked to Victoria, and that the two systems would operate independently through Herne Hill?

Click to expand...

I once thought about this. It makes sense in terms of pairing. But I think probably unpopular re loss of Victoria, even if it enabled less conflict and far more frequency.

You could have from the Blackfriars direction:
4tph Core - Orpington via Kent House (stopping) - and
4tph Core - Outer (fast to Bromley South) into Thameslink. Could be 2tph Medway via Sole St, and 2tph Ashford via Maidstone.

Maybe you could fit more - like a semi-fast pattern, run out of the Blackfriars bays. I would re-direct the Charing Cross - Maidstone to Dover Priory.
This takes on/over the Rainham paths.

---
Victoria is the interesting one. Ideally you would aim for:
8tph Victoria - Sutton (4 via Wimbledon, 4 via Streatham) - but you can handle much more on the Kent side - Orient Express aside. But it's underused today too.

Could you:
Redirect the Epsom/Dorking services via Herne Hill and then Hackbridge?
Add 2tph local to Norwood Junction / Beckenham Junction / Belmont (as that goes to 4tph) - via Herne and Tulse?
Shift some of the locals (via Balham) onto the dreaded P7/8?

If this very contentious change was ever made, what could you add -or what frequency increases would make it worthwhile?

Dr_Paul said:

Perhaps a tram station could be built on the curve leading to Wimbledon station; there seems to be sufficient space at the north-east end of the old Wimbledon down yard to build one.

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There’s a design on the shelf (going dusty) for exactly that!

PGAT said:

I disagree that having the trams terminate at the main station was a mistake. It makes for easier interchange as well

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I'm not suggesting that trams shouldn't serve the station, just that they shouldn't occupy space that could otherwise be used for trains. Something akin to East Croydon would be ideal, though a quick look on Google Maps doesn't make it look easy to "crayon" a workable route. Wimbledon is also a terminus which would be more awkward from a safety point of view if running at street level.

If the trams could be moved away from platform level (the "how" probably needs it's own thread) this would mean the second Sutton loop platform could be reinstated. This would remove one of the timetable constraints.

Am I remembering correctly that one of the factors at play in keeping the loop as part of Thameslink was political lobbying of some sort? I vaguely recall that initially Sutton loop services were at some point planned to (following the Thameslink 2000 upgrade) terminate in the bays at Blackfriars, but I could well be mistaken.
As an aside, is the Sutton Loop the only reason for the subfleet of 8-car 700s? Or are there other short platforms on the MML route to the north?

61653 HTAFC said:

Am I remembering correctly that one of the factors at play in keeping the loop as part of Thameslink was political lobbying of some sort? I vaguely recall that initially Sutton loop services were at some point planned to (following the Thameslink 2000 upgrade) terminate in the bays at Blackfriars, but I could well be mistaken.
As an aside, is the Sutton Loop the only reason for the subfleet of 8-car 700s? Or are there other short platforms on the MML route to the north?

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Plenty more in South London too - Catford Loop and some of the Kent places - and the Orpington / Kent House routes in peaks, all 8.

That lobbying thing is so old now, I'm sure the change could be made today.

61653 HTAFC said:

Am I remembering correctly that one of the factors at play in keeping the loop as part of Thameslink was political lobbying of some sort?

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Kind of. There was a very active petition against the proposal, and that was then supported by the Wimbledon MP, Stephen Hammond (who is actually quite a reasonable chap). The DfT had literally hundreds if not thousands of letters objecting to the proposal in the consultation.

61653 HTAFC said:

As an aside, is the Sutton Loop the only reason for the subfleet of 8-car 700s? Or are there other short platforms on the MML route to the north?

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No. Lots of stations across the TL network that can’t take more than 8 coaches, indeed some that can’t take 8. Hatfield, WGC, Kentish Town, Cricklewood, Hendon, and loads south of the river.

Would removing the crossover at Herne Hill even allow for a much higher frequency of services than now?

The timetable already allows for the Thameslink service through Herne Hill to be doubled in frequency to 8tph without any effect on Southeastern services, there are only two bays at Blackfriars so it wouldn't be possible to have that many services terminate there (I assume the absolute maximum would be 8tph), and of course the major issue along the Chatham Main Line is that the mix of stopping and express services means that not much else can fit (and removing all the stops along the main line or Catford loop isn't really tenable).

I do think the idea of extending the Victoria Line to Herne Hill (on a loop with a single platform) and closing Brixton mainline station would have quite a bit of merit - as well as the obvious benefits of the extension for the local area, it would significantly increase efficiency/throughput on the Victoria Line, and removing the Brixton stop on the Chatham Main Line might allow for a doubling of express services between Victoria and Bromley South, by flighting two non-stop services 3 minutes apart just before a stopper.

NCT said:

To the OP - do you mean remodelling Herne Hill, such that West Dulwich is locked to Blackfriars and Tulse Hill is locked to Victoria, and that the two systems would operate independently through Herne Hill?

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Yes, that’s the entire point of my proposal! Was it not clear from the outset?

squingo44 said:

Yes, that’s the entire point of my proposal! Was it not clear from the outset?

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Have to admit it took a bit of deduction to work out what you were getting at.

London Trains said:

Would removing the crossover at Herne Hill even allow for a much higher frequency of services than now?

The timetable already allows for the Thameslink service through Herne Hill to be doubled in frequency to 8tph without any effect on Southeastern services, there are only two bays at Blackfriars so it wouldn't be possible to have that many services terminate there (I assume the absolute maximum would be 8tph), and of course the major issue along the Chatham Main Line is that the mix of stopping and express services means that not much else can fit (and removing all the stops along the main line or Catford loop isn't really tenable).

I do think the idea of extending the Victoria Line to Herne Hill (on a loop with a single platform) and closing Brixton mainline station would have quite a bit of merit - as well as the obvious benefits of the extension for the local area, it would significantly increase efficiency/throughput on the Victoria Line, and removing the Brixton stop on the Chatham Main Line might allow for a doubling of express services between Victoria and Bromley South, by flighting two non-stop services 3 minutes apart just before a stopper.

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I would remove all the stops on the Catford loop once the Bakerloo Line Extension to Hayes opens and use it to run all the express services to Victoria, then run a high frequency stopping service between Bromley and Blackfriars via West Dulwich.

Blackfriar’s terminating platforms can handle a lot more than 8tph, provided the overall service is segregated and doesn’t interline much with our services. I reckon at least 24 TPH should be possible. A rail depot would be necessary, of course.

Sutton loop trains going to Victoria via Herne Hill would be fine, I think. The only passengers who would need to transfer at Herne Hill to go to Victoria would be the ones from the stations between Shortlands and West Dulwich - the rest would still have express services available to them.

squingo44 said:

Blackfriar’s terminating platforms can handle a lot more than 8tph, provided the overall service is segregated and doesn’t interline much with our services. I reckon at least 24 TPH should be possible. A rail depot would be necessary, of course.

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Not possible with buffer stops even with tube-style operation and signalling. The Victoria line can terminate everything on 2 platforms because of over-running tunnels allowing trains to arrive at full speed. The Jubilee line needs 3 platforms at Stratford to turnaround 24tph.

Magdalia said:

Given that Streatham South junction is in a residential area I think there is zero chance of grade separation there. There is also no prospect of grade separation at Sutton. The second platform at Wimbledon was given up for the tram so that's another bottleneck difficult to remove.

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You might be right about Streatham South. But then again, there are examples of grade separated junctions on commuter lines throughout the London network, and there’s definitely space around the area of the junction.

Wimbledon would be easier to achieve when you take into account the fact that it’s going to be expanded anyway for XR2, it wouldn’t be hard to fit another platform in.

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NCT said:

Not possible with buffer stops even with tube-style operation and signalling. The Victoria line can terminate everything on 2 platforms because of over-running tunnels allowing trains to arrive at full speed. The Jubilee line needs 3 platforms at Stratford to turnaround 24tph.

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Ah. Is the current limit at Blackfriars much lower than that?

NCT said:

Have to admit it took a bit of deduction to work out what you were getting at.

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I see, I should have worded my proposal a little more clearly then.

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Thebaz said:

Not 100% following this. How are they getting to Victoria? There'd still be conflicting moves at Herne Hill unless you sent them via Streatham North Junction. But who in their right mind would board a Victoria via Balham service at Wimbledon/Haydon's Road/Tooting when there are far more efficient ways of getting there?

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They’d go via Brixton, taking over the Chatham Main Line approach to Victoria

== Doublepost prevention - post automatically merged: 5 Jun 2026 ==

cle said:

I once thought about this. It makes sense in terms of pairing. But I think probably unpopular re loss of Victoria, even if it enabled less conflict and far more frequency.

You could have from the Blackfriars direction:
4tph Core - Orpington via Kent House (stopping) - and
4tph Core - Outer (fast to Bromley South) into Thameslink. Could be 2tph Medway via Sole St, and 2tph Ashford via Maidstone.

Maybe you could fit more - like a semi-fast pattern, run out of the Blackfriars bays. I would re-direct the Charing Cross - Maidstone to Dover Priory.
This takes on/over the Rainham paths.

---
Victoria is the interesting one. Ideally you would aim for:
8tph Victoria - Sutton (4 via Wimbledon, 4 via Streatham) - but you can handle much more on the Kent side - Orient Express aside. But it's underused today too.

Could you:
Redirect the Epsom/Dorking services via Herne Hill and then Hackbridge?
Add 2tph local to Norwood Junction / Beckenham Junction / Belmont (as that goes to 4tph) - via Herne and Tulse?
Shift some of the locals (via Balham) onto the dreaded P7/8?

If this very contentious change was ever made, what could you add -or what frequency increases would make it worthwhile?

Click to expand...

I like where you’re coming from with these ideas - but surely a single stopping pattern between Blackfriars and Bromley would maximise the frequency uplift? I was thinking of an all stops service that would branch off to Orpington or to Swanley.

On the Sutton Loop, there’s not really a limit on service frequency at the Victoria terminus, so I’d try and push frequencies up beyond 8 TPH to 12 or 16 TPH and do whatever is necessary to make that possible - interventions at Wimbledon station and Streatham South Junction.

== Doublepost prevention - post automatically merged: 5 Jun 2026 ==

NCT said:

Not possible with buffer stops even with tube-style operation and signalling. The Victoria line can terminate everything on 2 platforms because of over-running tunnels allowing trains to arrive at full speed. The Jubilee line needs 3 platforms at Stratford to turnaround 24tph.

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Since the Jubilee Line can turn around 24 TPH with 3 platforms, and the platform reoccupancy time for a 3 platform terminal station must be higher for an equivalent station with only 2 platforms, doesn’t that mean that Blackfriars’ two terminating platforms ought to be able to accommodate at least 16TPH?

I suppose that the station approach time would be shorter because of there being fewer crossovers, but the speed of the approach could be lower and the trains would be longer.

Charing Cross and Cannon Street average around a 10min platform reoccupancy time, so by being super strict on dwell times it might be possible to squeeze out 8 mins at Blackfriars. Which would give us 120/8=15 TPH maximum terminating at Blackfriars, or 12 TPH if you wanted to keep some capacity spare.

Alternatively, we could build an extra two platforms at Blackfriars.

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Come to think of it, this proposal doesn’t make much sense if it doesn’t provide massive increases in service frequencies along the affected lines. An increase from a theoretically possible 8 TPH to 12 TPH wouldn’t be worth the effort. So my proposal would have to also include additional terminating platforms at Blackfriars to support a proper metro-frequency service between Blackfriars and Bromley.

squingo44 said:

Blackfriar’s terminating platforms can handle a lot more than 8tph, provided the overall service is segregated and doesn’t interline much with our services. I reckon at least 24 TPH should be possible.

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The practical maximum at Blackfriars bays is 10 tph.

Planning rules require 8 mins turn back time, plus 3 mins platform reoccupation. And most moves require an extra 1/2 min on approach adjustment time compared to the usual running time, and departures need to be on the whole minute. So 12 mins between departures from each platform.