Future of Third Rail

[zwk500]

They're both 25 miles of unelectrified track and see more or less similar passenger numbers.

Marshlink: Three Oaks ~10k, Doleham ~3k, Winchelsea ~10k, Rye ~475k, Appledore ~40k, Ham Street ~90k
Oxted: Edenbridge T: ~300k, Hever ~50k, Cowden ~50k, Ashurst ~40k, Eridge ~120K, Crowborough ~350k, Buxted ~120k, Uckfield ~450k (Pre-Covid Annual Avg Entry/Exit).
Total Marshlink Passenger numbers: ~628k, Oxted (Uckfield branch): 1,480k.

The Uckfield branch serves more than 2x as many people on the stations it serves alone. Not forgetting that Uckfield services also offer the fast service from Oxted to London as well as serving the East Croydon-London Bridge on the way, whereas Marshlink serves Eastbourne and Hastings with another stopping service. It's just not in the same league.

Also, electrifying Uckfield would avoid placing stress on a heavily laden power system in inner London as well as smooth out paths in a vey congested part of the network by allowing uniform performance (171s are slightly slower off the mark as DMUs). Although there is scope to charge the batteries East Croydon-Oxted and in the downtime at London Bridge, it's still operationally tight. Whereas Eastbourne-Hastings is fine for a unit to slowly charge up on the way.

If anything, you would electrify the Marshlink line more as that opens the doors for HS1 services into Rye and Hastings.

No it doesn't, there's not enough pointwork to get from Marshlink to HS1 without shunting. And by the time you've doddled along on the single line into Hastings you're not going to be much time up on the existing service. HS1 to Hastings died when Amber Rudd left parliament.

 

[A0]

They're both 25 miles of unelectrified track and see more or less similar passenger numbers. If anything, you would electrify the Marshlink line more as that opens the doors for HS1 services into Rye and Hastings.

Bit in bold - not without a load of other infrastructure work on the Marshlink e.g. long distance of single track. So that's not happening.

Whereas Uckfield is a genuine diesel island which electrification would improve matters operationally.

 

[MarkyT]

No it doesn't, there's not enough pointwork to get from Marshlink to HS1 without shunting. And by the time you've doddled along on the single line into Hastings you're not going to be much time up on the existing service. HS1 to Hastings died when Amber Rudd left parliament.

Indeed. You might just be able to add sufficient new pointwork to allow HS1 trains to get across to platform #2, less likely #1 to access Marshlink, but it would be an expensive, disruptive job, and it wouldn't be any faster to Hastings from London than a limited stop service on the traditional route via Tonbridge so I doubt BCR would ever add up. Keep it self-contained with BEMU and maybe extend back to Brighton to achieve a greater proportion of mileage on 3rd rail.

http://townend.me/files/ashford.pdf

 

[43066]

No it doesn't, there's not enough pointwork to get from Marshlink to HS1 without shunting. And by the time you've doddled along on the single line into Hastings you're not going to be much time up on the existing service. HS1 to Hastings died when Amber Rudd left parliament.

Plus the 395s are quite stretched as it is, without sending some of them on an amble along the “sheep, shoot* and shingle” line!

* actually a different word beginning with S

EDIT: as an aside, I believe Amber Rudd’s influence was responsible for the limited stop “Hastings Express” peak time workings on the SE classic lines, which ran fast between London Bridge and High Brooms. I doubt those have survived Covid…

 

[zwk500]

Indeed. You might just be able to add sufficient new pointwork to allow HS1 trains to get across to platform #2, less likely #1 to access Marshlink, but it would be an expensive, disruptive job, and it wouldn't be any faster to Hastings from London than a limited stop service on the traditional route via Tonbridge so I doubt BCR would ever add up. Keep it self-contained with BEMU and maybe extend back to Brighton to achieve a greater proportion of mileage on 3rd rail.

http://townend.me/files/ashford.pdf

As neat as your diagrams are, The CHX-Ramsgates use 5 and 6 so your design would cause a major operational re-write of the station.

 

[MarkyT]

As neat as your diagrams are, The CHX-Ramsgates use 5 and 6 so your design would cause a major operational re-write of the station.

Indeed! I drew these up years ago when the idea was being discussed, but I don't actually support the concept at all.

 

[mr_jrt]

The equipment in most real installations doesn't life expire at the same moment though. So at any given time a large amount of capital plant equipment will have to be discarded early if a conversion occurred.

Nonsense. You recover what still has life in it, and reuse it elsewhere.

Given that some of the most intensely operated railways in Britain are third rail, I am somewhat skeptical.

People far more knowledgeable than you or I have stated on this very forum that some of the newer units (the Desiros, IIRC) have had to be current-limited on DC to prevent them blowing out the power supplies, and that there is a hard limit on how many of them can be in section at once. Likewise, heavy freight trains are massively limited on the third rail sections, to the point I think they just run on their diesel engines.

In addition future technologies are likely to reduce 25kV's power delivery advantage.
See the talk about superconductors.

I look forward to my shares in Bionic Duckweed Inc. going to the moon.

Stock you can't use because it's not cleared for the railway anyway.
Given that cascades are not particularly important in the modern era, I am skeptical this is at all a significant factor.

It's almost certainly a darn sight easier and more cost effective to get spare rolling stock based upon one of the major families (Aventra, Desiro, etc) cleared than to get new DC units built whilst simultaneously sending spare AC units for scrap.

Indeed the 9kV trial is potentially very interesting.

But if superconducting cables prove a success it does raise questions about the optimum voltage for a DC overhead electrification system.

1500V or 3000V are likely to be perfectly adequate in a superconducting system and have lower clearances etc.
DC OHL does have the advantage of being able to coexist with third rail for long periods, so an overlay could be implemented without interfering with the regular system.

I predict precisely zero chance of yet another incompatible micro standard being put in place. The costs of such a tiny installation would be astronomical. I'm afraid it'll either be self-propelled with batteries (perhaps with a diesel top up), the existing legacy 3rd rail equipment, or standard OHLE.

 

[RobShipway]

I predict precisely zero chance of yet another incompatible micro standard being put in place. The costs of such a tiny installation would be astronomical. I'm afraid it'll either be self-propelled with batteries (perhaps with a diesel top up), the existing legacy 3rd rail equipment, or standard OHLE.

It could be OHLE, but with the trains having battery backup within them so that they can power through the gaps where OHLE is not able to be inserted.

 

[JonathanH]

It would be interesting to know why it wasn’t electrified along with the rest of the coastway in the 1930s - low traffic levels presumably.

Well, the railways at Ashford weren't electrified until the late 1950s and the Tonbridge to Hastings line until 1986, so it wasn't a diesel island in the 1930s.

I think the answer to your question is here, that is that for the traffic on offer between Ashford and Hastings, it was easier in 1958 to build four diesel units than electrify the line, and that the line narrowly escaped closure ten years later. https://www.kentrail.org.uk/hastings_3.htm

A full diesel service from London to Hastings via Tunbridge Wells was implemented on 9th June 1958. Eventually, it was decided not to pursue electrification between Ashford and Hastings, and in 1958 four DEMU sets, two vehicles in length, were built for the route. Dieselisation had seen the removal of the locomotive turntable and coal stage at Hastings station in 1957.

Opposition to these plans was substantial, enough to ensure the retention of services between Ashford and Hastings, but not enough to keep the New Romney branch on the timetable. Just two years later, in August 1969, closure of the Ashford to Hastings line was again announced, and passenger trains would be withdrawn once a replacement bus service had been organised. Criticism of the proposal was just as severe as that in 1967, and campaigning once again saved the route from being axed. Retention of services between Ashford and Hastings was formally given the green light in July 1974, but would be at the cost of route rationalisation. This started on 29th April 1979, with the singling of the line between Appledore and Ore. A passing loop was retained at Rye, and colour lights installed throughout on the line. Singling was deemed complete on 30th September 1979, and the line signalled using the Tokenless Block System.

 

[43066]

Well, the railways at Ashford weren't electrified until the late 1950s and the Tonbridge to Hastings line until 1986, so it wasn't a diesel island in the 1930s.

I think the answer to your question is here, that is that for the traffic on offer between Ashford and Hastings, it was easier in 1958 to build four diesel units than electrify the line, and that the line narrowly escaped closure ten years later. https://www.kentrail.org.uk/hastings_3.htm

Thanks for this - I had a dig around on Kentrail yesterday, but somehow missed this!

 

[MarkyT]

Well, the railways at Ashford weren't electrified until the late 1950s and the Tonbridge to Hastings line until 1986, so it wasn't a diesel island in the 1930s.

Nowhere in the UK would have been a 'diesel island' in the 1930s, regardless of electrification status!

 

[Peter Sarf]

People do seem to keep conveniently forgetting in these discussions that equipment doesn't have infinite lifespans. There is a cost to leaving the DC electrification as it is, and you need to take that off the cost of any conversion works. That's the actual important cost differential.

== Doublepost prevention - post automatically merged: 10 Apr 2023 ==


Are they rather limited, though? You gain the ability draw many, many, many more amps, enabling longer and more frequent trains, for a start. You also gain the ability to use rolling stock from a much larger pool.

The replacement equipment for 25kV AC would also have a finite lifespan so very roughly the same depreciation as the DC equipment it replaces. So no long term justification possible but still the ideal opportunity to convert presents if a significant part of a DC third rail route comes up for renewal at the same time. I suppose some parts not life expired (transformers) could be conveniently re-used on other DC routes ?.

Not just equipment, - structures on the railway have finite lives as well. So the overbridges and tunnels that were built in the 19th century will eventually need replacing or major reconstruction as the previous practice of patching-up has reached the end of the road. The number of bridges with insufficient OLE clearanceon 'ancient' mainlines is steadily reducing, often because the nature of the road traffic has mandated their replacement. Then there's the advances in insulation and OLE integration that enable easier installation of wiring without rebuilding (as would have been the case a few decades ago).

Piecemeal conversion of 3rd rail to OLE has progressively been eased over the last 20 years with the frequent provision (passive or actual) since ac OLE power supply provision on DC targetted EMUs was adopted by the RoSCos. If considering the current 'modern' fleet, in a quick rough estimate, there are 872 multiple units that operate on 750VDC 3rd rail track and have been built with provision for conversion to run under 25kV ac OLE. Of that total, 290 are running as dual voltage trains so do not need further work (with the exception of adding pantographs to the 707s of them which I imagine is a depot task). The remainder of the total would require a modification/retrofit programme.
With the considerable population of ready to run DV stock, it would possible to undertake a programme of incremental conversion to ac power by tackling certain sections of mainlines first where the returns would be the greatest. That might be the heaviest used sections probably with the most high speed running, e.g. BML and SWML.

Now there is a thought. So I reckon the most likely to get converted from 3rd rail to OHLE is the part of DC land that is nearest to non DC land !. The SWML is a longer route with more freight and inter-regional services which would benefit. If a conversion were to start it would have to be in SW land.

They're both 25 miles of unelectrified track and see more or less similar passenger numbers. If anything, you would electrify the Marshlink line more as that opens the doors for HS1 services into Rye and Hastings.

I think the Marshlink route is a far more borderline case than Uckfield. Surely a lot less passengers both potential or actual ?. Marshlink does not have a service to London and could never justify 10 coach trains to London whereas Uckfield sees 10-car diesel trains to London. Uckfield gets mentioned in conversations about extending the line beyond (re-opening). Marshlink evaded closure threats even after the Beeching era.

 

[RobShipway]

The replacement equipment for 25kV AC would also have a finite lifespan so very roughly the same depreciation as the DC equipment it replaces. So no long term justification possible but still the ideal opportunity to convert presents if a significant part of a DC third rail route comes up for renewal at the same time. I suppose some parts not life expired (transformers) could be conveniently re-used on other DC routes ?.

Now there is a thought. So I reckon the most likely to get converted from 3rd rail to OHLE is the part of DC land that is nearest to non DC land !. The SWML is a longer route with more freight and inter-regional services which would benefit. If a conversion were to start it would have to be in SW land.

I think the Marshlink route is a far more borderline case than Uckfield. Surely a lot less passengers both potential or actual ?. Marshlink does not have a service to London and could never justify 10 coach trains to London whereas Uckfield sees 10-car diesel trains to London. Uckfield gets mentioned in conversations about extending the line beyond (re-opening). Marshlink evaded closure threats even after the Beeching era.

I think that it is more likely that you will have Reading West to Southampton done first in DC land. However, I suspect that the section from Reading West to Basinsgtoke will be AC OHLE, then from Basinstoke to Southampton on DC OHLE, with any freight locomotive having the ability to change from AC to DC OHLE and vice versa. Uckfield would be more of a challenge especially with one of the tunnels on the route, which I believe to be quite narrow.

You may in future find an OHLE charging point at Uckfield (Oxted Line) to recharge battery units, but the main OHLE would not start until the train go to Hurst Wood. Then I believe it would be DC OHLE, unless you are converted the East Grinstead line over to AC OHLE at the same point in time.

 

[A0]

Now there is a thought. So I reckon the most likely to get converted from 3rd rail to OHLE is the part of DC land that is nearest to non DC land !. The SWML is a longer route with more freight and inter-regional services which would benefit. If a conversion were to start it would have to be in SW land.

It will also be where the electrical load causes problems - and the SWML has been cited for that previously as a challenge to running the freight services from Southampton using electric traction.

The one thing more modern rolling stock procurement has usefully achieved is that virtually all units are capable of operating on both 3rd rail and 25kv. The challenge with moving from 3rd rail to OHLE would primarily be in London where various lines converge. But with dual voltage rolling stock you could work to a point on 3rd rail and then switch over - which with the SWML could be Basingstoke or Woking.

I'd also be looking at Kent as another possibility for conversion done in stages, so:

Swanley and Tonbridge to Ashford.
Ashford to Dover and Ramsgate via Canterbury West.
Swanley to Ramsgate and Faversham to Dover (including Sheerness and Gravesend).
Paddock Wood - Strood.
Sevenoakes - Tunbridge Wells / Hastings / Ore.

That would leave 3rd rail in the vicinity of London - do something similar on other lines and eventually you'll reach a point where removing 3rd rail in London makes sense as well.

I think the Marshlink route is a far more borderline case than Uckfield. Surely a lot less passengers both potential or actual ?. Marshlink does not have a service to London and could never justify 10 coach trains to London whereas Uckfield sees 10-car diesel trains to London. Uckfield gets mentioned in conversations about extending the line beyond (re-opening). Marshlink evaded closure threats even after the Beeching era.

Reopening beyond Uckfield won't happen despite what many crayonistas believe - mainly because it never comes up with a sensible business case or use - it's always the "diversionary route" argument, which won't make it viable.

 

[zwk500]

It will also be where the electrical load causes problems - and the SWML has been cited for that previously as a challenge to running the freight services from Southampton using electric traction.

The one thing more modern rolling stock procurement has usefully achieved is that virtually all units are capable of operating on both 3rd rail and 25kv. The challenge with moving from 3rd rail to OHLE would primarily be in London where various lines converge. But with dual voltage rolling stock you could work to a point on 3rd rail and then switch over - which with the SWML could be Basingstoke or Woking.

I'd also be looking at Kent as another possibility for conversion done in stages, so:

Any conversion strategy would want to minimise the number of changeovers in service so my strategy would be:
Wessex:
- Basingstoke-Southampton-Weymouth (with Botley and St Denys as in-service changeovers).
- Havant-Botley/St Denys/Portsmouth
- Guildford-Havant
- (much more dubious value Pirbright Jn area-Basingstoke.
This gets the London-Coast stuff done, leaving AFARP services either all 3rd-rail or with decent runs under the wires justifying the changes. You may also chuck in the Chichester-Havant section for a bit of extra 3rd rail removal
KENT:
- Maidstone East-Ashford-Canterbury West-Ramsgate
- Tonbridge-Ashford-Dover
- Dover-Ramsgate
Then, if you discovered an infinite source of money you could finish off the conversion of everything beyond Dartford and either Sevenoaks or Orpington.

Reopening beyond Uckfield won't happen despite what many crayonistas believe - mainly because it never comes up with a sensible business case or use - it's always the "diversionary route" argument, which won't make it viable.

On it's original alignment yes, which sadly means on any alignment, yes. It's a shame because there's a small town of 5k+ that could easily be served with a minor diversion then joining the mainline at Glynde, facing Brighton, which would facilitate Oxted line travel to Brighton (not an insubstantial draw by any means) as well as providing relief capacity with a relatively straightforward reverse at Lewes for additional Seafords or Eastbournes should they be desired.

 

[Meerkat]

Is there any real need to switch over the suburban and particularly the inner suburban services? Slower speeds, better segregation from trespassers, fewer level crossings, less interaction with AC areas, plus many more, tighter, bridges and tunnels and complicated junctions to increase costs etc etc.

 

[A0]

Is there any real need to switch over the suburban and particularly the inner suburban services? Slower speeds, better segregation from trespassers, fewer level crossings, less interaction with AC areas, plus many more, tighter, bridges and tunnels and complicated junctions to increase costs etc etc.

AC has lower transmission loss, is less risky for anyone working trackside and most rolling stock can work 25kv as it's far more commonly used away from metro systems.

I'm not sure why anyone thinks persisting with a system which wasn't safe when first introduced in the Victorian times, is a good idea now over 100 years later.

 

[MarkyT]

Is there any real need to switch over the suburban and particularly the inner suburban services? Slower speeds, better segregation from trespassers, fewer level crossings, less interaction with AC areas, plus many more, tighter, bridges and tunnels and complicated junctions to increase costs etc etc.

AC has lower transmission loss, is less risky for anyone working trackside and most rolling stock can work 25kv as it's far more commonly used away from metro systems.

I'm not sure why anyone thinks persisting with a system which wasn't safe when first introduced in the Victorian times, is a good idea now over 100 years later.

On the other hand, much of the inner suburban 3rd rail network is little different in character to many metros. Nobody is calling for Met or District Underground lines to be converted, so maybe certain national network branches at least could also retain ground conductors, with suitable safeguards, even if the main trunks in and out of the termini eventually get overhead wires.

 

[HSTEd]

Nonsense. You recover what still has life in it, and reuse it elsewhere.

A lot of the capital plant value will be in things that are destroyed if you try to move them.

You can't move cable troughing or those wall mounted racks London Underground have without destroying the bulk of their in place value, as an eaxmple.

Cables aren't really worth pulling up for redeployment for only a few years worth of remaining life, if they are pulled up they will probably go for scrap.
Grid supply points can't easily be moved a hundred miles or anything like that.

You might be able to move rectifiers and circuit breaker equipment, but that is a relatively small part of the cost of these schemes in the modern era. It gets even worse, given that the parts of the third rail system most often proposed for conversion (the Weymouth line) uses a totally different electrical supply concept to that seen in earlier projects, so a lot of the equipment is of limited usefulness. Later third rail schemes do not have the lineside 33kV feeders.

I look forward to my shares in Bionic Duckweed Inc. going to the moon.

Bionic duckweed is a joke in a way that superconductors most certainly aren't.

The latter is not subject to inherent limits in the UKs biomass production capability, and there is far more experience of superconductors in industry than biodiesel fueled engines.

It's almost certainly a darn sight easier and more cost effective to get spare rolling stock based upon one of the major families (Aventra, Desiro, etc) cleared than to get new DC units built whilst simultaneously sending spare AC units for scrap.

How many electric Aventras or Desiros exist without the capability to be rigged for third rail?
I don't think it is very many.

Indeed, arguably, third rail capable stock is in even greater surplus than AC-only stock.

I predict precisely zero chance of yet another incompatible micro standard being put in place. The costs of such a tiny installation would be astronomical. I'm afraid it'll either be self-propelled with batteries (perhaps with a diesel top up), the existing legacy 3rd rail equipment, or standard OHLE.

1500V or 3kV are hardly micro standards, they are two of the most widely used electrification standards in the world! Equipment for such installations are commodity items, just like 25kV systems.

In europe attempts to upgrade DC overhead wiring are moving away from conversion to AC (given the enormous costs and timescales, a situation projected to worsen in future) and towards higher voltage DC solutions.
Serious work is being conducted to develop a new unified DC overhead line standard.

It is certainly most likely that the systems remain at 750V, but converison to DC overhead line is more likely than conversion to 25kV, because the chance of conversion to 25kV is zero.

The costs of 25kV schemes are now so large that no business case can ever be made, the fantasies about Brighton Main Line conversion were based on the magical HOPS train, which never delivered what was promised.

 

[Bald Rick]

I would say that making the change from 3rd rail to OHLE, would actually in many cases give you the ability to increase the line speed above 100mph

It would remove one constraint. There would still be scores of others…

Basingstoke-Weymouth is the only section at serious threat of conversion, and that has a large amount of very specific factors that make conversion worth thinking about.

it’s not under serious threat of conversion!

Uckfield is probably justified, but Marshlink looks ideal for a Battery unit (or battery / 3rd rail hybrid) with charging capability at Ashford.

They’ll both be batteries.

Also, electrifying Uckfield would avoid placing stress on a heavily laden power system in inner London as well as smooth out paths in a vey congested part of the network by allowing uniform performance (171s are slightly slower off the mark as DMUs). Although there is scope to charge the batteries East Croydon-Oxted and in the downtime at London Bridge, it's still operationally tight.

Inner London power supply isn’t as strained as it once was. Also, Battery EMUs would have the same performance as straight EMUs. The modelling shows plenty of scope for recharging from Hurst Green to London and back. A short ‘opportunity’ charge point at Uckfield supplied by a ‘trickle charged’ lineside battery would help.

Indeed. You might just be able to add sufficient new pointwork to allow HS1 trains to get across to platform #2, less likely #1 to access Marshlink, but it would be an expensive, disruptive job, and it wouldn't be any faster to Hastings from London than a limited stop service on the traditional route via Tonbridge so I doubt BCR would ever add up. Keep it self-contained with BEMU and maybe extend back to Brighton to achieve a greater proportion of mileage on 3rd rail.

http://townend.me/files/ashford.pdf

I may have said this before, but that layout isn’t possible on the ground. Also there’s the small matter of down services ex Tonbridge calling at Ashford…

 

[HSTEd]

I'm not sure why anyone thinks persisting with a system which wasn't safe when first introduced in the Victorian times, is a good idea now over 100 years later.

As opposed to spending tens of billions of pounds for a comparatively minor safety improvement?

The cost, and disruption, would be astronomical.

 

[MarkyT]

I may have said this before, but that layout isn’t possible on the ground. Also there’s the small matter of down services ex Tonbridge calling at Ashford…

You did at the time! zwk500 said the same about down trains from Tonbridge crossing to #5 and #6. I think you said some sort of connection from HS1 to Marshlink might fit plausibly, but it's all academic now, and quite rightly IMHO.

 

[Meerkat]

AC has lower transmission loss, is less risky for anyone working trackside

How much lower over inner suburban distances, and how much work is done trackside on live lines on inner suburbs? Is that improvement worth the massive cost of sorting all the bridges, tunnels and junctions, and the blockade costs of conversion?

 

[zwk500]

it’s not under serious threat of conversion!

Well, any threat compared to the rest of the network.

Inner London power supply isn’t as strained as it once was. Also, Battery EMUs would have the same performance as straight EMUs.

Both fair points.

The modelling shows plenty of scope for recharging from Hurst Green to London and back. A short ‘opportunity’ charge point at Uckfield supplied by a ‘trickle charged’ lineside battery would help.

When I did a tiny bit of work for it a few years ago I was told that was not the case. Of course, battery tech has advanced since then and service levels have changed.

I'm not sure why anyone thinks persisting with a system which wasn't safe when first introduced in the Victorian times, is a good idea now over 100 years later.

There aren't many people who know what they're on about who think it's a good idea, only that it's not worth switching away from it while we have bigger fish to fry in Bristol, Manchester, Birmingham etc.

How much lower over inner suburban distances, and how much work is done trackside on live lines on inner suburbs? Is that improvement worth the massive cost of sorting all the bridges, tunnels and junctions, and the blockade costs of conversion?

A lot more work could be down without isolations if it was OLE, because instead of it waiting to trip you up at ankle height the live part is 5m overhead. Is it worth the cost of doing the work? No - as evidenced by the lack of any serious plan to do anything about it.

 

[Bald Rick]

When I did a tiny bit of work for it a few years ago I was told that was not the case.

The modelling I saw a few years back (not by you, I’m sure of that ) had a few assumptions in it that were distinctly pessimistic.

 

[zwk500]

The modelling I saw a few years back (not by you, I’m sure of that ) had a few assumptions in it that were distinctly pessimistic.

I was timetable not power, so I'm fairly sure you didn't see my output on that sense-check (you'd know if you had, I took the opportunity to slip some suggestions in )

 

[Mikey C]

As opposed to spending tens of billions of pounds for a comparatively minor safety improvement?

The cost, and disruption, would be astronomical.

Just the thought of converting Clapham Junction and all the lines around it to OHLE brings me out in a cold sweat

 

[Railsigns]

I wonder if people realise just how much AC overhead electrification there once was in south London, before the impossible happened and it was all replaced with a completely different form of electrification.

 

[paul1609]

Uckfield, Marshlink and North Downs/Blackwater (the only signficant third rail gaps) are all within the range of battery EMUs running today in other countries

Other 3rd rail isn't likely to go anywhere.

The problem is that as far as Im aware none of the battery EMUs are charging in use off 750 vdc. The East Grinstead Line didn't (pre pandemic) have enough supply capacity for the Uckfield trains to be straight electric, let alone for charging batteries after running a return 50 miles off the juice.
With Marshlink the Brighton to Ashford Cycle didn't have sufficient power to recover the battery drain of the unnelectrified section. The proposed Electrostar conversion would have required a large fleet of battery conversions so that they could do a return trip to Seaford in between Ashford trips. Don't think that North downs has even been considered.

== Doublepost prevention - post automatically merged: 12 Apr 2023 ==

Marshlink: Three Oaks ~10k, Doleham ~3k, Winchelsea ~10k, Rye ~475k, Appledore ~40k, Ham Street ~90k
Oxted: Edenbridge T: ~300k, Hever ~50k, Cowden ~50k, Ashurst ~40k, Eridge ~120K, Crowborough ~350k, Buxted ~120k, Uckfield ~450k (Pre-Covid Annual Avg Entry/Exit).
Total Marshlink Passenger numbers: ~628k, Oxted (Uckfield branch): 1,480k.

Rather ignores that Marshlink is a through service. Theres significant education based commuting to Ashford (and on to Canterbury) which doesn't appear in your figures. I can tell you for a fact that more people get off the Marshlink train at Hampden Park for a connection to Brighton than remain on the train to Eastbourne. On my football home trips down to Pompey I more often than not carry some elderly persons suitcase over the richty footbridge at hampden who are going from Margate to Worthing avoiding London at all costs (and the cost). Theres significant "plus HS1" flows from the hastings conurbation especially if the destinations North or East of London. I reckon you can at least double if not triple the internal Marshlink figures for total passengers on the line.

 

[zwk500]

I wonder if people realise just how much AC overhead electrification there once was in south London, before the impossible happened and it was all replaced with a completely different form of electrification.

At 6.6KV AC, but yes it was done.

The problem is that as far as Im aware none of the battery EMUs are charging in use off 750 vdc. The East Grinstead Line didn't (pre pandemic) have enough supply capacity for the Uckfield trains to be straight electric, let alone for charging batteries after running a return 50 miles off the juice.
With Marshlink the Brighton to Ashford Cycle didn't have sufficient power to recover the battery drain of the unnelectrified section. The proposed Electrostar conversion would have required a large fleet of battery conversions so that they could do a return trip to Seaford in between Ashford trips. Don't think that North downs has even been considered.

@Bald Rick is far more versed in power supply levels than I, and I'm fairly sure he's said all 3 could easily cope with charging on these boards before. On a separate project I was involved in the rolling stock people were talking about geofencing charging areas for the proposed battery stock, so there are plenty of options.

Rather ignores that Marshlink is a through service.

Not so much ignoring as deliberately excluding because there's no hard numbers unless you have access to the LENNON database.

Theres significant education based commuting to Ashford (and on to Canterbury) which doesn't appear in your figures.

I'm not disagreeing with you, but I grew up in East Sussex and knew plenty of people who would commute between various combinations of Brighton, Lewes, Eastbourne and Hastings for college but very, very few who went between Hastings and Ashford (and that person lived in Rye).

I can tell you for a fact that more people get off the Marshlink train at Hampden Park for a connection to Brighton than remain on the train to Eastbourne.

This I can easily believe - the Marshlink DMUs were noticeably busy when they ran through to Brighton, and reportedly had caused a dramatic upsurge in use of the line.

Theres significant "plus HS1" flows from the hastings conurbation especially if the destinations North or East of London. I reckon you can at least double if not triple the internal Marshlink figures for total passengers on the line.

The problem here is that your 'significant' may well not be as high as you feel from your anecdotal evidence. Even so, doubling Marshlink usage doesn't break through the Uckfield line usage, and that's before we add in the Oxted fast numbers as well as people using it between South Croydon and London Bridge.
However, a key indicator of busyness: Uckfield trains justified investment to achieve 10-car formations. Marshlink can only take 4-car formations. If Marshlink was as busy or busier than Uckfield, why would it have trains less than half as long?