Upgrading the Chiltern Line

[AlexSJW]

Stations are not necessarily near any 'hefty' electric cables. A simple station can be fed from the grid as a domestic supply. A busier station may have a bigger connection but still doubtful it'd be of any use for electric charging (unless you went through the 'trickle-charge a shore reservoir and dump' option, which has it's own downsides)

You also need time to charge.

For third rail, yes. I don't see any 25KV AC OLE being taken down, primarily because we don't really have enough of it as is. I can, however, see lines that should be electrified being skipped because of batteries (frustratingly).

Heavy electricity lines are invariably in built up areas, not in open countryside. Not erecting OLE on the Chiltern will save a fortune. The DfT did state a few years ago they will not be extensively installing OLE looking into other forms such as battery-electric hybrids, etc.
Merseyrail has around seventy miles of 3rd rail. I can all that being removed for battery trains. Apart from the rail tunnel under the Mersey which has very steep inclines which OLE can be used. Trains can top up the batteries at stations as they go along if need be, using OLE technology.

Manufacturers state that their trains can reach high speeds on batteries with long ranges, such that the Chiltern can use battery hybrids. Battery hybrids could be used on the London to Chester route on HS2 track. The thirty miles of line from Crewe to Chester is unelectrified, where batteries could take over.

 

[Zomboid]

The power demand of electric traction is a completely different order of magnitude to a station. And it still has to obey the laws of physics (conservation of energy). If it takes 1MWh to move a train 10km in 10 minutes, then that has to be delivered one way or another. If it's a fully electrified route then that's 0.1MWh from the OLE per minute, if it's delivered in 1 minute at a station stop then that's 1MWh per minute followed by 9 minutes of 0.

If Marylebone is full of trains charging their batteries at the same time, it's going to need a lot of short term power rating. Way more than the supply that runs the lights, PIS, Burger shop etc, all of which will be a relatively constant load.

 

[SynthD]

Would it be worthwhile running a 15-minute frequency Lizzie service to Gerrards Cross, Beaconsfield and High Wycombe (with some calls at Denham and other intermediate stations), and then running all services from beyond High Wycombe non-stop from there to Marylebone?

Those two ideas wouldn't mix well. If there were the passing places necessary, Chiltern alone might make better use of them.

Marylebone is by St Johns substation, West Ruislip is near Uxbridge Moor substation, both 400kv. Lower supplies are near all the main stations further north.

 

[md2016]

The other fact is that Chiltern have been ok running extremely short trains for a London commuter route. 5 or 6 max usually!

When the new batt/AC stock comes, if it is in multiples of 4... 8 car trains would blow their minds and see capacity met.

I think this is the answer. I was thinking long term if GBR wants to accellerate elecrtrification/ reduce amount of rolling stock. The layout at Old Oak Common would make this extremely difficult/ costly however.
More likely that expanded capacity comes from new battery rolling stock and an eventual interchange at Old Oak Common. Clearing trains out from the Marylebone tunnels will hopefully allow more semi-fast peaks from High Wycombe, Gerrards Cross and Marylebone, whilst also allowing more regular Metros and fast services if demand is still there post HS2.

 

[zwk500]

Heavy electricity lines are invariably in built up areas, not in open countryside.

What do you mean by 'heavy'?

High-voltage lines run through the countryside to connect power stations to cities. Many railway feeder stations are connected to the national grid in the open countryside.

Not erecting OLE on the Chiltern will save a fortune.

Correct

Merseyrail has around seventy miles of 3rd rail. I can all that being removed for battery trains. Apart from the rail tunnel under the Mersey which has very steep inclines which OLE can be used. Trains can top up the batteries at stations as they go along if need be, using OLE technology.

Why do you think OLE isn't used in the tunnel? FWIW I cannot see 3rd rail being removed from much of the Merseyrail network, maybe the fringes where it'd interact with OLE. It certainly won't be replacing 3rd rail with OLE (not least because AIUI the 777s can only do 3rd rail + 25KV or 3rd rail + Battery, as the batteries go where the transformers do.

I think areas of the Southern region are at a far higher risk of de-electrification.

Manufacturers state that their trains can reach high speeds on batteries with long ranges, such that the Chiltern can use battery hybrids.

They do. And batteries are maturing all the time. So there will be many areas where batteries are used. The question is how to achieve the sensible balance of charging opportunities to operational practicality.

Battery hybrids could be used on the London to Chester route on HS2 track. The thirty miles of line from Crewe to Chester is unelectrified, where batteries could take over.

That's a line that wouldn't be electrified, rather than OLE being taken down, but it's also a digression from the topic.

 

[Zomboid]

I really don't see any de-electrification on a significant scale happening. It's much more efficient to draw power from the OLE/ 3rd rail as it's needed than to carry batteries around. And the power has to come from somewhere, you could de-electrify 20 miles (which will come at a cost) and then have to spend twice as much as the opex you've saved reinforcing what's left to support charging the batteries, so you're just spending money to move equipment from one place to another for no particular benefits, but a new requirement to fit batteries to trains that previously didn't need it. Maybe there will be certain situations where it'd make sense (such as dual voltage trains to make the change overs easier) but there won't be many IMO.

To try and stay on topic, the Chiltern line could well be electrified for battery trains, and if so it'll be designed as such.

 

[Mgameing123]

Those two ideas wouldn't mix well. If there were the passing places necessary, Chiltern alone might make better use of them.

Marylebone is by St Johns substation, West Ruislip is near Uxbridge Moor substation, both 400kv. Lower supplies are near all the main stations further north.

Though to be fair an Elizabeth Line service to High Wycombe would be very useful. It would also help move services out of Marylebone but the problem with this proposal is that it would probably require quad tracking if you want to run a train every 15 minutes.

== Doublepost prevention - post automatically merged: 17 Jun 2026 ==

Except that we go full circle to NIMBY mania - good luck getting those of Beaconsfield and Gerrards Cross on board with mass housebuilding. Or developing all these golf courses...

High Wycombe has seen development. Bicester has happened regardless. Aylesbury is too far but again developing. I'm not sure where else you could.

Perhaps Denham and more of High Wycombe?

 

[AlexSJW]

Heavy electricity supplies are around built up areas. Overhead lines are costly to maintain. Batteries substitute well and cheaply. As I wrote: The DfT did state a few years ago they will not be extensively installing OLE looking into other forms such as battery-electric hybrids, etc.

All Merseyrail Metro extensions are planned to be hybrid battery trains. Their new fleet of trains are designed to take batteries.

 

[zwk500]

Heavy electricity supplies are around built up areas.

Please can you define 'heavy' in the context of an electricity supply.

As I wrote: The DfT did state a few years ago they will not be extensively installing OLE looking into other forms such as battery-electric hybrids, etc.

What are you responding to here? The whole premise of this thread is that all-line electrification is off the table.

All Merseyrail Metro extensions are planned to be hybrid battery trains. Their new fleet of trains are designed to take batteries.

They're designed to take Batteries or 25KV AC Electrification.

 

[squingo44]

Would four tracking between South Ruislip and Denham be feasible?

 

[Zomboid]

Would four tracking between South Ruislip and Denham be feasible?

How much money do you want to spend? Doesn't look like it would need wide scale demolition outside the railway boundary, but the trackbed and a lot of bridges would need widening north of West Ruislip.

 

[zwk500]

Would four tracking between South Ruislip and Denham be feasible?

Depends what you mean by feasible

It'd require:
- Remodelling of the flying junction (Northolt Junction) just south of South Ruislip
- Rebuilding of Up Platform at South Ruislip to take back the old Up Slow/Relief line trackbed
- Possible slues of London Underground and/or Chiltern between South and West Ruislip
- Rebuilding of Down platform at West Ruislip to take back the old Down Slow/Relief line trackbed.
- Almost definite slues of London Underground and Chiltern just outside West Ruislip
- Possible rebuilding of underline structures at the extreme end of the LU Headshunt beyond W. Ruislip
- Rebuilding/Doubling River Pinn & Footpath underbridge
- Rebuilding/Doubling Breakspear Road South underbridge
- Rebuilding Harvill Road overbridge (google shows currently under construction)
- Possible Rebuilding Skip Lane overbridge (google shows currently under construction)
- Rebuilding/Doubling Grand Union Canal Underbridge
- Possible works to River Colne Underbridge
- Rebuild of down platforms at Denham to clear path for fast lines.
not to mention
- All land purchase required
- handover of some of HS2 site to Chiltern
- all associated earthworks to wide the formation where necessary
- complete replacement of signalling and pointwork to accomodate crossovers between tracks and junctions for access at West Ruislip to LU depot and South Ruislip to waste sidings/Greenford Branch.
- all associated permissions to do the work
- all associated funding to complete the work.
- any and all culverts etc that aren't visible from Google Maps satellite view.

TLDR: Nothing that hasn't been done elsewhere, but in the current climate certainly not an 'easy win'.

 

[MarlowDonkey]

Would four tracking between South Ruislip and Denham be feasible?

It used to be four tracks between South and West Ruislip. From West Ruislip to Denham, it had been proposed in the 1936-40 scheme to extend the Central Line, presumably on segregated tracks.

Being able to terminate Chiltern trains at Old Oak Common is a more likely development. From Old Oak Common to South Ruislip it would just duplicate the Central Line if you had a stopping service.

 

[Bald Rick]

If it takes 1MWh to move a train 10km in 10 minutes

… then it’s a very heavy, or very fast train!

Then I'll be able to provide you with a timescale for an answer, and fee of course

£110 an hour is the going rate.

I’ll do it for £109.99/h

 

[The Planner]

I’ll do it for £109.99/h

You're internal, normal NR off charging to another project for you!

 

[Zomboid]

… then it’s a very heavy, or very fast train!

Very heavy, it's doing 60km/h

 

[Bald Rick]

You're internal, normal NR off charging to another project for you!

BR Inc. Side hustle.

 

[zwk500]

£110 an hour is the going rate.

I’ll do it for £109.99/h

You're internal, normal NR off charging to another project for you!

I'm not telling you what rates my company actually charges me out for, but it's competitive even against @Bald Rick's generous discount

 

[AlexSJW]

Depends what you mean by feasible

It'd require:
- Remodelling of the flying junction (Northolt Junction) just south of South Ruislip
- Rebuilding of Up Platform at South Ruislip to take back the old Up Slow/Relief line trackbed
- Possible slues of London Underground and/or Chiltern between South and West Ruislip
- Rebuilding of Down platform at West Ruislip to take back the old Down Slow/Relief line trackbed.
- Almost definite slues of London Underground and Chiltern just outside West Ruislip
- Possible rebuilding of underline structures at the extreme end of the LU Headshunt beyond W. Ruislip
- Rebuilding/Doubling River Pinn & Footpath underbridge
- Rebuilding/Doubling Breakspear Road South underbridge
- Rebuilding Harvill Road overbridge (google shows currently under construction)
- Possible Rebuilding Skip Lane overbridge (google shows currently under construction)
- Rebuilding/Doubling Grand Union Canal Underbridge
- Possible works to River Colne Underbridge
- Rebuild of down platforms at Denham to clear path for fast lines.
not to mention
- All land purchase required
- handover of some of HS2 site to Chiltern
- all associated earthworks to wide the formation where necessary
- complete replacement of signalling and pointwork to accomodate crossovers between tracks and junctions for access at West Ruislip to LU depot and South Ruislip to waste sidings/Greenford Branch.
- all associated permissions to do the work
- all associated funding to complete the work.
- any and all culverts etc that aren't visible from Google Maps satellite view.

TLDR: Nothing that hasn't been done elsewhere, but in the current climate certainly not an 'easy win'.

But what are the side benefits to other services? Which overall may make it feasible.

 

[zwk500]

But what are the side benefits to other services? Which overall may make it feasible.

'It depends'

Unhelpful answer, but it's true. If you were talking about the current timetable, there's no benefit as trains don't get stuck around Ruislip. If you were trying to fit extras around the existing timetable, then the current trains wouldn't really move. If you recast the timetable you might get more benefits, but would be dependent on whether you could e.g. have a Birmingham and Oxford run fast through Denham on minimum headway in the time it takes one stopper to call at the 3 stations.
A quick fiddle on RTT suggests that the stopping penalty across the 3 stations is not sufficient to let a fast overtake without waiting for an extended time at Denham.

 

[squingo44]

But what are the side benefits to other services? Which overall may make it feasible.

Every Chiltern service would have interchange with the Elizabeth line at South Ruislip, so anyone from long distance services would be able to quickly transfer to an Elizabeth line train.

 

[zwk500]

Every Chiltern service would have interchange with the Elizabeth line at South Ruislip, so anyone from long distance services would be able to quickly transfer to an Elizabeth line train.

If you stop the fast services as well, you'll need longer dwells in the slow services that still go to Marylebone. The trade-offs just don't appear to be adding up here.

 

[squingo44]

If you stop the fast services as well, you'll need longer dwells in the slow services that still go to Marylebone. The trade-offs just don't appear to be adding up here.

Bruh what about all the additional connectivity to central London?

High Wycombe to Canary Wharf direct?

Leamington Spa to Liverpool Street with one interchange?

 

[zwk500]

Bruh

Please grow up.

what about all the additional connectivity to central London?

A very good question.

High Wycombe to Canary Wharf direct?

Canary Wharf is the Docklands, not Central London.

Leamington Spa to Liverpool Street with one interchange?

Liverpool Street is the City. Both of those places are almost exclusively for people working in the finance or related industries based in the City or Docklands. That's not actually that bigger connectivity (note Crossrail always talked about connecting Canary Wharf to Heathrow, not other people to Canary Wharf).
Tottenham Court Road is the central London Crossrail stop.

Also worth pointing out that there is zero chance of trains from Chiltern operating into the Crossrail Core. That point has been passed.
The proposal would be to interchange at South Ruislip for the following stopper to then interchange again at Old Oak Common, against continuing in to Marylebone where you have a direct interchange to the Bakerloo and an indirect interchange to the Sub-Surface lines and Jubilee Line.

I suspect it'll be quicker for anybody on Oxford or Birmingham services to get to their ultimate destination by going non-stop to Marylebone than to change twice, especially given that the interchange at OOC is unlikely to be any smoohter than getting into the Underground network.

 

[squingo44]

Also worth pointing out that there is zero chance of trains from Chiltern operating into the Crossrail Core. That point has been passed.

What makes you say this? Are the plans for Old Oak Common too set in stone?

 

[zwk500]

What makes you say this? Are the plans for Old Oak Common too set in stone?

Yes, the platforms have been at least partially built.

 

[Bald Rick]

What makes you say this? Are the plans for Old Oak Common too set in stone?

It’s half built!

 

[MatthewHutton]

It’s half built!

Doesn’t the south ruislip to Old Oak Common line not still interact with the slow tracks coming out of Paddington?

 

[SynthD]

Doesn’t the south ruislip to Old Oak Common line not still interact with the slow tracks coming out of Paddington?

No, it was cut specifically for this work.

 

[Bald Rick]

Doesn’t the south ruislip to Old Oak Common line not still interact with the slow tracks coming out of Paddington?

It went years ago, and the design for OOC prevents reinstatement.