Low speed crossovers with strong cases for upgrade

[brad465]

Crossing over between fast/main and slow/relief lines obviously obstructs multiple lines at once, especially where the lines are in pairs rather than parallel. Therefore, low speed moves obstruct more lines for longer and act as a bottleneck.

The following examples come to mind as ones that if it were possible to upgrade would improve performance and capacity:

-Parks Bridge Jct (Up slow to Up fast/Down fast to Down slow): currently 15mph and used by at least 2tph in each direction changing lines, plus at least a further 8tph off peak through the area. It's angle is impeded by two bridges with structures that prevent crossovers on it, however Brookbank Rd appears to be a dead end now leading into a school ground, so in theory has no traffic (and if it's a regular school entrance, a summer/Christmas holiday blockade could replace it without school disruption). If this was replaced and the junction extended enough to allow 30-40mph, this would make a big difference.
-Crossover by Grove Park depot (Down fast to down slow): 15-20mph? and used by some of the Charing X-Maidstone/Ashford, plus peak extras to/from Orpington that are fast between London Bridge and Grove Park. Not as strong as the first example, but with 70mph on both pairs of lines, remodelling here reduces the braking/acceleration and shortens journeys through here. Might be impeded by points into the depot though.

 

[The Planner]

Crossing over between fast/main and slow/relief lines obviously obstructs multiple lines at once, especially where the lines are in pairs rather than parallel. Therefore, low speed moves obstruct more lines for longer and act as a bottleneck.

The following examples come to mind as ones that if it were possible to upgrade would improve performance and capacity:

-Parks Bridge Jct (Up slow to Up fast/Down fast to Down slow): currently 15mph and used by at least 2tph in each direction changing lines, plus at least a further 8tph off peak through the area. It's angle is impeded by two bridges with structures that prevent crossovers on it, however Brookbank Rd appears to be a dead end now leading into a school ground, so in theory has no traffic (and if it's a regular school entrance, a summer/Christmas holiday blockade could replace it without school disruption). If this was replaced and the junction extended enough to allow 30-40mph, this would make a big difference.
-Crossover by Grove Park depot (Down fast to down slow): 15-20mph? and used by some of the Charing X-Maidstone/Ashford, plus peak extras to/from Orpington that are fast between London Bridge and Grove Park. Not as strong as the first example, but with 70mph on both pairs of lines, remodelling here reduces the braking/acceleration and shortens journeys through here. Might be impeded by points into the depot though.

Remember that its also the signalling that may need altering to reduce any MAR/release from red restrictions, the fact that faster S&C is bigger and may not fit and also if OLE is there will need that tinkering with too. They are quite often bigger jobs than many think. Your Brookbank Road example being a case in point. If the bridge isn't knackered, the benefits from raising the line speed really need to sell something.

 

[Bald Rick]

I’ve spent a good chunk of my career looking at this, and have had quite a few successes in doing this (you can thank me later). As @The Planner says signalling does complicate matters somewhat, as does OLE.

My vote goes to Cricklewood South Junction. That is only the speed it is today (20) because the money ran out on the West Hamsptead resignalling project in the late 70s.

 

[bramling]

I’ve spent a good chunk of my career looking at this, and have had quite a few successes in doing this (you can thank me later). As @The Planner says signalling does complicate matters somewhat, as does OLE.

My vote goes to Cricklewood South Junction. That is only the speed it is today (20) because the money ran out on the West Hamsptead resignalling project in the late 70s.

The slow/fast crossovers immediately north of Finsbury Park. Used at least 4 times per hour in each direction. Good few seconds saving in each direction, which presumably would add up to something useful.

Potters Bar DF to DS, which eventually had a flashing yellow sequence added just before it ceased to be regularly used.

A faster entry and exit between Letchworth sidings reception roads and the station would be useful too, especially now this is being used through the day.

90mph crossovers at Woolmer Green Junction and 90mph on the slow lines from there to Hitchin would have given me a few days extra on my life over the years too.

 

[Bald Rick]

The slow/fast crossovers immediately north of Finsbury Park. Used at least 4 times per hour in each direction. Good few seconds saving in each direction, which presumably would add up to something useful.

They are 30, the saving would literally be a couple of seconds given that almost everything using them is stopping. More benefit southbound obvs.

 

[brad465]

Remember that its also the signalling that may need altering to reduce any MAR/release from red restrictions, the fact that faster S&C is bigger and may not fit and also if OLE is there will need that tinkering with too. They are quite often bigger jobs than many think. Your Brookbank Road example being a case in point. If the bridge isn't knackered, the benefits from raising the line speed really need to sell something.

Parks Bridge has annoyingly just had a resignalling through there (2020) so a remodel can't be tied in with that. There's no OLE here though which helps, and while the bridge replacement will be difficult, the example one is small and has minimal traffic (unlike the bridge the other side which has the A20 under it). If this junction is to be upgraded, the best chance going forward would likely be if the Bakerloo line makes it to Hayes and its mainline connections are severed; this will have a level of resignalling and junction work already baked in, so efficient working here is possible. I think the high service frequency through here helps increase the benefits, while Lewisham station provides a diversion during the disruptive works required.

 

[bramling]

They are 30, the saving would literally be a couple of seconds given that almost everything using them is stopping. More benefit southbound obvs.

I guess there’s an element of wishful thinking on my part given I’ve been using the northbound crossover for the best part of 40 years. However wouldnt the saving be a bit more than a couple of seconds given that virtually every train using it is now a 12-car? A higher speed crossover would allow unrestricted acceleration. Having said this, the layout is a bit odd on the down side, so wonder how easy a 70mph crossover would actually be to fit here.

 

[Magdalia]

The slow/fast crossovers immediately north of Finsbury Park. Used at least 4 times per hour in each direction. Good few seconds saving in each direction, which presumably would add up to something useful.

As a long time user of GN services calling at Finsbury Park I can't let this pass without comment.

On the up road things are much worse now than they were before the up side island was reinstated.

In ye olden dayes many trains called in the up fast platform, and, compared with this, the new crossovers add about a minute to journey time. The old crossover into what was then platform 1 was about half a minute quicker than what we have now.

But the issue is not with the crossovers it is with the signalling, the approach control is much more severe than it used to be.

 

[The Planner]

Not crossovers, but any loop with entry and exit speeds of 20mph or less.

 

[Bald Rick]

But the issue is not with the crossovers it is with the signalling, the approach control is much more severe than it used to be.

Indeed, and will be solved by ETCS.

Which brings a whole new dimension to this issue, ie crossovers where faster speeds cant be achieved because of restrictive approach control today, but where a higher speed could be achieved without the approach control.

 

[bramling]

Indeed, and will be solved by ETCS.

Which brings a whole new dimension to this issue, ie crossovers where faster speeds cant be achieved because of restrictive approach control today, but where a higher speed could be achieved without the approach control.

Thinking of the southern end of the ECML, places where this may have some day-to-day benefit
* Holloway UF to US
* Finsbury Park as already mentioned
* Biggleswade DF to DS occasionally
* Is the approach to Huntingdon on the up still approach controlled?

These are the only ones which readily spring to mind. No doubt there’d be plenty of others coming into play during disruption.

 

[Magdalia]

Indeed, and will be solved by ETCS

I was hoping that you would come along and say that!

Is the approach to Huntingdon on the up still approach controlled?

It is a long while since I did this.

Huntingdon would benefit from a 70mph turnout, but even better would be a slow line from Conington.

 

[Bevan Price]

Fast to Slow lines connections North of Stafford station, particularly for southbound trains; removing need for approach control could probably save 1-2 minutes. Current slow start northbound from Stafford until slow to fast line connection could be avoided, saving about 1 minute.

 

[The Planner]

Fast to Slow lines connections North of Stafford station, particularly for southbound trains; removing need for approach control could probably save 1-2 minutes. Current slow start northbound from Stafford until slow to fast line connection could be avoided, saving about 1 minute.

I doubt Doxey will ever get changed. If it was going to be done it would have happened as part of the resig. Unless you are a 125mph capable train you are arguably better off staying on the slows.