Will there ever be anymore third rail locos?

[Class73Electro]

Something I've been thinking of recently, recent locomotives now tending towards bi/tri modes, but always overhead line for power, will there ever be a third rail capable loco developed? The last was the 92 (correct me if I am wrong - I'm not including the 373) and before that only the 73s (still going strong!) and the 74. Will it always just be diesel power on the third rail network?

Is it at all feasible to run freight on third rail?

Thanks!

 

[CMS1]

Third rail isn't going anywhere so yes there will be. Batteries might become standard to improve acceleration, regen braking, and to cover power failures.
Another question, could batteries increase top speed on the 3rd rail lines?

 

[Bletchleyite]

Third rail isn't going anywhere so yes there will be. Batteries might become standard to improve acceleration, regen braking, and to cover power failures.
Another question, could batteries increase top speed on the 3rd rail lines?

It's already possible to go to 100mph on third rail so I doubt there's much need. I think above that is affected by the dynamics of the third rail pickup?

 

[Sorcerer]

Another question, could batteries increase top speed on the 3rd rail lines?

It might increase top speed of third rail traction, but on the lines themselves absolutely no chance. You need to draw a lot of power to reach high speed, and third rail simply cannot provide that; the old Eurostar fleet were power-hungry monsters just running at normal third rail speed. Batteries are a non-factor in that regard.

Of course if you meant to ask whether batteries could allow trains to run faster on routes using third rail without actually using the rail itself, then theoretically I suppose you could. But then you'd have speed differences that would eat up valuable capacity. It'd also drain the battery a lot faster as you use more power to increase your speed.

 

[HSTEd]

If the railway actually wants to eliminate diesel use, it will have to order freight locomotives with third rail capability.

 

[Sun Chariot]

Third rail isn't going anywhere so yes there will be.

If the railway actually wants to eliminate diesel use, it will have to order freight locomotives with third rail capability.

Which services do you see this being viable for?

I'm unconvinced by the financial and operating cases to have new locomotives with compatability for 750v DC third rail.

Freight paths over the third rail network: operating mileage is comparatively small; quick look at WTT paths which run over third rail line: all those paths travel far greater mileage under 25kv AC - so make more sense to use diesel and / or battery power whilst pathed along third rail network.

The full costs to design, build and maintain a discreet fleet of locos operating 750v DC + 25Kv AC, for relatively small traffic flows over a small 750v DC mileage, does not make financial viability in my mind.

 

[BerkshireRails]

This is an idea of a new build third rail loco I had.

Which services do you see this being viable for?

I'm unconvinced by the financial and operating cases to have new locomotives with compatability for 750v DC third rail.

Freight paths over the third rail network: operating mileage is comparatively small; quick look at WTT paths which run over third rail line: all those paths travel far greater mileage under 25kv AC - so make more sense to use diesel and / or battery power whilst pathed along third rail network.

The full costs to design, build and maintain a discreet fleet of locos operating 750v DC + 25Kv AC, for relatively small traffic flows over a small 750v DC mileage, does not make financial viability in my mind.

I can think of some workings just on the third rail network 4Y19 Mountfeild to Southampton which has been run by a pair of 73s. In addition there is 6Y83 & 6Y82 Southampton to Tonebridge, 7X43 & 0Y43 Eastleigh to Hoo Junction are just to name a few workings.

 

[Tazi Hupefi]

Third rail isn't going anywhere so yes there will be. Batteries might become standard to improve acceleration, regen braking, and to cover power failures.
Another question, could batteries increase top speed on the 3rd rail lines?

That's not correct, third rail will be definitely and quite enthusiastically be removed in some locations once Southeastern gets it's new and cascaded rolling stock, particularly in depots and locations with hostile operating conditions like tunnels, viaducts and bridges, and areas with higher levels of crime such as trespass.

Steve White has been talking about this in various bits and pieces recently in fact.

Whether third rail stays in other areas will depend on how successful the technology is with having it automatically switch off when a train isn't in the section. Batteries with convenient fast charge locations offer a compelling and cost effective alternative now, especially when overhead electrification isn't viable because of the infrastructure limitations.

Third rail expansion is simply not going to ever happen now.

It's a case of how much of it is converted to battery charging infrastructure.

 

[HSTEd]

Which services do you see this being viable for?

I'm unconvinced by the financial and operating cases to have new locomotives with compatability for 750v DC third rail.

Freight paths over the third rail network: operating mileage is comparatively small; quick look at WTT paths which run over third rail line: all those paths travel far greater mileage under 25kv AC - so make more sense to use diesel and / or battery power whilst pathed along third rail network.

750V capability would lead to a meaningful reduction in the amount of infrastructure necessary to obtain freight decarbonisation.

There would be no need for any charging infrastructure at all on the southern Region!

As an example, a freight locomotive covering the Mendips to Brighton or somewhere with a Jumbo stone train would need a substantially increased number of batteries to do it without third rail.

The full costs to design, build and maintain a discreet fleet of locos operating 750v DC + 25Kv AC, for relatively small traffic flows over a small 750v DC mileage, does not make financial viability in my mind.

The cost of 750v capability on a 25kV locomotive is going to be pretty small with modern technology. Especially if it's a battery electric locomotive.

 

[Sun Chariot]

As an example, a freight locomotive covering the Mendips to Brighton or somewhere with a Jumbo stone train would need a substantially increased number of batteries to do it without third rail.

The cost of 750v capability on a 25kV locomotive is going to be pretty small with modern technology. Especially if it's a battery electric locomotive.

These mileages on third rail network, WTT pathed freights:

3rd rail mileage = 23 each way. 1800t gross.
6002 Merehead to Woking Yard.
6V22 Woking Yard to Merehead (return empties).
Note: Service runs only "as required"

3rd rail mileage = 27 each way. 1400t gross.
6052 Westbury to Chichester.
6V09 Chichester to Merehead (return empties).
Note: Service has only run 3 times since 1-Dec-2024

3rd rail mileage = 31 each way. 1600t gross.
4O08 Trafford Park to Southampton.
4O52 Masborough to Southampton.
Note: these paths and the other intermodal paths using this 3rd rail route, run as required

3rd rail mileage = 51 each way. 2000t gross.
6068 Westbury to Crawley.
6V68 Crawley to Merehead (return empties).
Note: Service runs as required, typically 2 to 3 pwk

3rd rail mileage = 54 each way. 1800t gross.
6040 Westbury to Ardingly (near Haywards Heath).
6V57 Ardingly to Whatley (return empties).
Note: Service has only run 2 times since 1-Dec-2024

Hoo to Eastleigh and Mountfield to Eastleigh paths, currently operated by GBRf 69s or 66s are, I agree, entirely over 3rd rail network (apart from certain sidings in the yards).

But the investment and operating case for a discrete fleet of 750v DC capable locomotives, for these mileages?

 

[CMS1]

That's not correct, third rail will be definitely and quite enthusiastically be removed in some locations once Southeastern gets it's new and cascaded rolling stock, particularly in depots and locations with hostile operating conditions like tunnels, viaducts and bridges, and areas with higher levels of crime such as trespass.

Yes aware of that, I thought the OP was alluding to 3rd rail to OHLE conversion, which with batteries is even less likely.

 

[Class15]

An Overhead/third rail/diesel loco would surely be brilliant for trains out of Southampton?

 

[BerkshireRails]

An Overhead/third rail/diesel loco would surely be brilliant for trains out of Southampton?

Something like the loco idea I came up with?

 

[zwk500]

An Overhead/third rail/diesel loco would surely be brilliant for trains out of Southampton?

An Overhead/Battery loco would be equally as suitable and much simpler design for the electronics though. It also wouldn't have to worry about keeping the third rail pickup clear of the lower sector gauge on non-third rail lines.

Fit charging bars at suitable points at Southampton, if you need to. Especially if Basingstoke-Reading was wired as well, it's about 50 miles from Basing to So'ton.

 

[Sun Chariot]

An an indication of costs with vs without 750v DC third rail pickup capability:

The order cost for forty-six class 92s, is quoted in the public domain as £345 million in current monetary value.

The order for thirty class 99s, is quoted in the public domain as £150 million in 2025 monetary value.

== Doublepost prevention - post automatically merged: 3 Sep 2025 ==

An Overhead/Battery loco would be equally as suitable and much simpler design for the electronics though. It also wouldn't have to worry about keeping the third rail pickup clear of the lower sector gauge on non-third rail lines.

Fit charging bars at suitable points at Southampton, if you need to. Especially if Basingstoke-Reading was wired as well, it's about 50 miles from Basing to So'ton.

+1 to this

 

[Trainbike46]

That's not correct, third rail will be definitely and quite enthusiastically be removed in some locations once Southeastern gets it's new and cascaded rolling stock, particularly in depots and locations with hostile operating conditions like tunnels, viaducts and bridges, and areas with higher levels of crime such as trespass.

Steve White has been talking about this in various bits and pieces recently in fact.

Whether third rail stays in other areas will depend on how successful the technology is with having it automatically switch off when a train isn't in the section. Batteries with convenient fast charge locations offer a compelling and cost effective alternative now, especially when overhead electrification isn't viable because of the infrastructure limitations.

Third rail expansion is simply not going to ever happen now.

It's a case of how much of it is converted to battery charging infrastructure.

I agree it is likely that third rail at high-risk locations will be removed in time.

However, a 3rd rail, OHLE, and battery locomotive would get value out the third rail kit, which as HSTEd points out is pretty cheap, because it would enable charging of the battery at many locations.

This is an idea of a new build third rail loco I had.
View attachment 187740

So, if I understand it correctly you are proposing a co-co-co locomotive. Why is it this big, if it doesn't have batteries?

 

[BerkshireRails]

So, if I understand it correctly you are proposing a co-co-co locomotive. Why is it this big, if it doesn't have batteries?

To keep route availability as low as possible as well as to prevent gapping in the third rail, I haven't decided if it will have batteries.

 

[43096]

An an indication of costs with vs without 750v DC third rail pickup capability:

The order cost for forty-six class 92s, is quoted in the public domain as £345 million in current monetary value.

The order for thirty class 99s, is quoted in the public domain as £150 million in 2025 monetary value.

That’s pretty much an irrelevant comparison as you’re comparing designs 30 years apart. Back when the 92s were ordered AC motor traction was a new development and their were specific - and costly - requirements around Channel Tunnel operation.

A better comparison would be between (for example) current production Vectron AC and Vectron MS. Third rail capability would cost a bit more but the AC vs MS comparison is a better starting point.

 

[JohnElliott]

Yes aware of that, I thought the OP was alluding to 3rd rail to OHLE conversion, which with batteries is even less likely.

Once all the trains had batteries with a range of a few miles it would make it much easier to do piecemeal conversions from third rail to overhead: it would be possible to have unelectrified gaps between the two systems rather than elaborate switchgear where they overlap.

 

[zwk500]

Once all the trains had batteries with a range of a few miles it would make it much easier to do piecemeal conversions from third rail to overhead: it would be possible to have unelectrified gaps between the two systems rather than elaborate switchgear where they overlap.

You'd want to convert more than a few miles at a time though. But batteries will have more than enough range to cover the section lengths you'd be considering .

 

[HSTEd]

An Overhead/Battery loco would be equally as suitable and much simpler design for the electronics though. It also wouldn't have to worry about keeping the third rail pickup clear of the lower sector gauge on non-third rail lines.

Fit charging bars at suitable points at Southampton, if you need to. Especially if Basingstoke-Reading was wired as well, it's about 50 miles from Basing to So'ton.

The electrification of Basingstoke to Reading alone would cost far more othan the cost increment of ensuring that the new fleet of 25kV/battery locomotives have third rail capability using retractable shoes.

== Doublepost prevention - post automatically merged: 3 Sep 2025 ==

An an indication of costs with vs without 750v DC third rail pickup capability:

The order cost for forty-six class 92s, is quoted in the public domain as £345 million in current monetary value.

The order for thirty class 99s, is quoted in the public domain as £150 million in 2025 monetary value.

Which is more to do with the fact that power electronics have advanced an awful lot in the last 35+ years.
A dual voltage battery locomotive today will have minimal cost increment over a 25kV/battery one.

 

[zwk500]

The electrification of Basingstoke to Reading alone would cost far more othan the cost increment of ensuring that the new fleet of 25kV/battery locomotives have third rail capability using retractable shoes.

Are you including in that the costs of bolstering the power system to account for the additional demand?

 

[BerkshireRails]

Which is more to do with the fact that power electronics have advanced an awful lot in the last 35+ years.
A dual voltage battery locomotive today will have minimal cost increment over a 25kV/battery one.

Also a class 92 is basically two locos in one for redundancy in the channel tunnel, plus the 92s have to have extra signalling like TVM-430.

 

[HSTEd]

Are you including in that the costs of bolstering the power system to account for the additional demand?

I made a simplistic assumption that upgrades on the third rail system avoid similar power supply upgrades on the 25kV system, plus the upgrades to power supplies necessary for any fast chargers. So that it would all come out approximately as a wash.

A battery locomotive charging on third rail will likely be able to eek out substantial amounts of power through voltage monitoring of course, possibly to a much greater degree than on 25kV.

Looking abroad, I don't think SNCF has procured an AC only locomotive in a very long time, which would seem to support my thesis that they are not that expensive.

 

[Peter Mugridge]

Looking abroad, I don't think SNCF has procured an AC only locomotive in a very long time, which would seem to support my thesis that they are not that expensive.

The most recent SNCF AC only locomotives, I think, are the class BB27300, built 2006 - 2008. They haven't bought any bi-mode locomotives more recently, but they have had a lot of bi-mode units.

 

[HSTEd]

The most recent SNCF AC only locomotives, I think, are the class BB27300, built 2006 - 2008. They haven't bought any bi-mode locomotives more recently, but they have had a lot of bi-mode units.

Wikipedia suggests they have 1500V capability but I must admit that I have no direct knowledge. The same "source" suggests that SNCF Fret is currently buying tri-voltage locomotives (25kV, 15kV and 1500V) as BB 37000.

 

[Peter Mugridge]

Wikipedia suggests they have 1500V capability but I must admit that I have no direct knowledge. The same "source" suggests that SNCF Fret is currently buying tri-voltage locomotives (25kV, 15kV and 1500V) as BB 37000.

Sorry, yes, they do have 1500V DC as well, I forgot about the mix of currents in the Paris area!!

 

[SynthD]

I haven't decided if it will have batteries.

It should have batteries. They are needed for the real world case of container cranes operating on trains. The battery performance doesn’t need to be good, as it is for private rail use, such as a container dock. A train that travels at 5mph on battery power until it reaches NR rail with OLE will meet some customers requirements.

 

[D365]

To keep route availability as low as possible as well as to prevent gapping in the third rail, I haven't decided if it will have batteries.

Why would a lack of traction batteries prevent gapping?

Besides, the traction system configuration of a locomotive is chosen by the customer, not the supplier.

 

[43096]

Wikipedia suggests they have 1500V capability but I must admit that I have no direct knowledge. The same "source" suggests that SNCF Fret is currently buying tri-voltage locomotives (25kV, 15kV and 1500V) as BB 37000.

SNCF is not buying locos (the BB37000s were delivered in 2004-6) currently and the Fret business has been heavily restructured so is unlikely to need any locos anytime soon.

The last AC only machines SNCF bought were the last BB15000 in 1978. The last DC only locos built for SNCF were BB7200 in 1985.