Will there ever be anymore third rail locos?

[BerkshireRails]

Why would a lack of traction batteries prevent gapping?

Being a longer loco would reduce the risk of gapping.

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.

I can see advantages in having batteries but also disadvantages of having batteries. It probably would have batteries.

Here is a very rough cab layout I came up with.

 

[MarkyT]

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.

Future all battery equipped fleets can certainly avoid undesirable dual electrified areas at the changeovers. The systems have very different earthing strategies. The rails in 750VDC only areas are not bonded to earth. They remain isolated from ground on plastic pads and clip inserts to encourage return current to remain in the running rails. In 25kVAC everything metalic in the corridor, including stanchions, electrical cabinets, station structures, bridge components etc, must be earthed for touch potential safety. Rails are also earthed; normally the 'traction rail' as opposed to the 'signalling rail', where that needs to be electrically isolated for track circuits. In axle counter areas, all rails can be frequently bonded to each other, and earth.

In dual electrified areas, the necessary 'compromise' is that comprehensive earthing must be installed for safety, which provides very many potential 'escape paths' for the DC return current to leak out, leading to the stray current taking alternative routes back to the substation, risking corrosion of metalwork and underground utilities en route, both within and outwith the railway boundary.

On Thameslink, I think the sheer complexity of the core changeover area, with all the metal-framed high value buildings, city streets and railway structures nearby forced the particular complicated switching solution to derisk this. In a rural location (not on a metal bridge!) this would be less of a concern and there are techniques for reinforcing the preferred return path with some parallel cabling to ensure the lowest possible loop resistance. This can reduce the leakage, but can't eliminate it entirely, as current spreads out along all possible paths, proportionally according to their resistance, so there's always some risk, more so under fault conditions where a preferred return path is interupted.

 

[HSTEd]

Future all battery equipped fleets can certainly avoid undesirable dual electrified areas at the changeovers. The systems have very different earthing strategies. The rails in 750VDC only areas are not bonded to earth. They remain isolated from ground on plastic pads and clip inserts to encourage return current to remain in the running rails. In 25kVAC everything metalic in the corridor, including stanchions, electrical cabinets, station structures, bridge components etc, must be earthed for touch potential safety. Rails are also earthed; normally the 'traction rail' as opposed to the 'signalling rail', where that needs to be electrically isolated for track circuits. In axle counter areas, all rails can be frequently bonded to each other, and earth.

In dual electrified areas, the necessary 'compromise' is that comprehensive earthing must be installed for safety, which provides very many potential 'escape paths' for the DC return current to leak out, leading to the stray current taking alternative routes back to the substation, risking corrosion of metalwork and underground utilities en route, both within and outwith the railway boundary.

On Thameslink, I think the sheer complexity of the core changeover area, with all the metal-framed high value buildings, city streets and railway structures nearby forced the particular complicated switching solution to derisk this. In a rural location (not on a metal bridge!) this would be less of a concern and there are techniques for reinforcing the preferred return path with some parallel cabling to ensure the lowest possible loop resistance. This can reduce the leakage, but can't eliminate it entirely, as current spreads out along all possible paths, proportionally according to their resistance, so there's always some risk, more so under fault conditions where a preferred return path is interupted.

In the longer term, the work that SNCF et al are doing on superconducting DC feeders may strongly mitigate leakage current concerns. Installation of an operational feeder is currently underway at Paris Montparnasse.

When you can bond the return rail (perfectly) to the substation 0V terminal every hundred metres or so, leakage current is not so much of an issue.

Plus, my understanding is that touch potentials on the running rails is normally the limitng factor on third rail distances to substations rather than voltage drop in the conductor rail.

 

[Sun Chariot]

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.

My post isn't seeking to give a technical comparison. I've no technical knowledge.
My post relates to my questions in posts 6 and 10 - yet to be answered - driven from the freight services two prior posters had cited as a justification for the Rough Order of Magnitude investment needed.

 

[Helvellyn]

The electric spine (who remembers that) was going to overhead wire the route from the Midlands to Southampton via Oxford, Reading and Basingstoke, with third rail removed Basingstoke to Southampton. The view was the 444s/450s were suitable for dual-voltage conversion and it'd get the Freightliner traffic from Southapton electrically hauled.

Add in the diversionary route via Laverstock and it'd have been easy to get to Salisbury. Then in-fill electrification would have been back on the agenda...

It's almost like there could have been a plan for a rolling electrification programme if poor industry cost controls hadn't kyboshed things.

 

[Class73Electro]

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 ==


+1 to this

Ouch! Though surely the high price of the 92s is more down to the Tunnel requirements then just third rail?

Do you not just need a AC-DC converter / transformer? or is it more complicated then that (I suspect probably!)

 

[stevieinselby]

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.
...
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.

The reason that SouthEastern are able to plan to remove the most problematic sections of live rail and use batteries instead is because most of the live rail will remain in place and so the trains can easily recharge their batteries on the move. I see no reason to believe they are planning widespread or large-scale removal of the live rail – removing the rail and adding lots of fast charge points would have a significant capital cost, and would give very little benefit beyond the most problematic and high-risk areas.

Removing electrification in favour of batteries is a very different scenario from not installing electrification in favour of batteries.

 

[D365]

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.

In other words… discontinuous electrification.

 

[Class15]

I understand discontinuous electrification on currently unelectrified routes, but why on currently electrified routes?

 

[zwk500]

I understand discontinuous electrification on currently unelectrified routes, but why on currently electrified routes?

Third rail is a major safety hazard to anybody on track, and in complicated junctions can impost limits on what pieces of equipment can be effectively used as it blocks access to one side of the tracks.

If the entire fleet is battery-equipped, third rail could be removed from a problem section without risk of gapping the trains but with almost no noticeable change in performance or power demand. Consider also areas such as level crossings or depots.

 

[AndrewE]

If the entire fleet is battery-equipped, third rail could be removed from a problem section without risk of gapping the trains but with almost no noticeable change in performance or power demand. Consider also areas such as level crossings or depots.

... just as long as they can switch between power sources on the move with no delays!

 

[zwk500]

... just as long as they can switch between power sources on the move with no delays!

Indeed! I expect BEMUs operating in the third rail area will be using blended power most of the time anyway to ease peak load on the traction supply system, but it is still a very valid concern.

 

[HSTEd]

Personally I'd envisage a future battery freight locomotive to either be a Bo-Bo-Bo or a Bo-Bo+Bo-Bo (articulated but still a normal length overall). That would allow it to carry the heavy batteries with minimum track damage and such, which is likely to be a concern given costs of labour etc in the future.

25kV, retractable third rail pickup and fast charger capability. Honestly I'd enquire about the cost of a 750V or 1500V overhead line capability, but I doubt it would be economic.
A battery freight train can probably even make use of tram wiring without undue current draws if it just draws continuously.

 

[renegademaster]

I can't see the long distance aggregate freight ever going third rail, it runs mostly under AC and the current rating will be too weak for heavy trains. GBRF will use their 99s for that kind of work and just run the relatively short third rail sections on diesel.

The 73s are getting very old now , all though a reckon a lot of the RHTT trains will soon be run with cascaded sheds, eventually they'll need replacing and maybe a new battery or third rail loco will come out then

 

[BerkshireRails]

I can't see the long distance aggregate freight ever going third rail, it runs mostly under AC and the current rating will be too weak for heavy trains. GBRF will use their 99s for that kind of work and just run the relatively short third rail sections on diesel.

The 73s are getting very old now , all though a reckon a lot of the RHTT trains will soon be run with cascaded sheds, eventually they'll need replacing and maybe a new battery or third rail loco will come out then

The replacement will need to fit in the Northern City Line tunnels with ETCS for the test train workings.

 

[zwk500]

The replacement will need to fit in the Northern City Line tunnels with ETCS for the test train workings.

Or DRS could take over with Class 88s, which are cleared without restriction

or fit monitoring gear to the passenger service fleet of 717s and avoid the need to run dedicated test paths, or have a bespoke monitoring regime by operatives instead of vehicles, or a combination of the above.

 

[D365]

Or DRS could take over with Class 88s, which are cleared without restriction
View attachment 187799

And, would you believe, were next in line for Freight ETCS fitment after the Class 66 and Class 67!

 

[HSTEd]

I can't see the long distance aggregate freight ever going third rail, it runs mostly under AC and the current rating will be too weak for heavy trains. GBRF will use their 99s for that kind of work and just run the relatively short third rail sections on diesel.

The 73s are getting very old now , all though a reckon a lot of the RHTT trains will soon be run with cascaded sheds, eventually they'll need replacing and maybe a new battery or third rail loco will come out then

Although it might appear distant at the moment, the end of the fossil fuel era in ground transport is coming rapidly.

When the road is decarbonised, burning diesel for routine freight operations is going to be expensive (as the bulk of the liquid fuel distribution apparatus will have ceased to exist) and politically..... problematic.

As noted, once a battery locomotive is in use, peak current draw is not going to be a huge problem on third rail because the train will be able to draw only the power that is available, independently of the output power at any moment.

 

[zwk500]

And, would you believe, were next in line for Freight ETCS fitment after the Class 66 and Class 67!

Is there a plan/list/timescale for freight ETCS Fitment publicly available anywhere? I'm not overly shocked more modern locos are jumping up in the queue but am slightly surprised, do DRS have much south of Peterborough that often?

 

[Trainbike46]

Is there a plan/list/timescale for freight ETCS Fitment publicly available anywhere? I'm not overly shocked more modern locos are jumping up in the queue but am slightly surprised, do DRS have much south of Peterborough that often?

Would it be needed for Nuclear Flask trains from Sizewell, or from the now-closed Dungeness and Bradwell plants (assuming there is any nuclear flask traffic left?)

Although it might appear distant at the moment, the end of the fossil fuel era in ground transport is coming rapidly.

When the road is decarbonised, burning diesel for routine freight operations is going to be expensive (as the bulk of the liquid fuel distribution apparatus will have ceased to exist) and politically..... problematic.

Absolutely agreed. The era of cheap diesel for the railway is going to end.

As noted, once a battery locomotive is in use, peak current draw is not going to be a huge problem on third rail because the train will be able to draw only the power that is available, independently of the output power at any moment.

A battery locomotive that can use OHLE, third rail, and a shore supply would be very useful. If you only provide batteries (no diesel), you could put a very significant amount of batteries in to bridge gaps, deal with terminals, and as you say, supplement the third rail supply as needed.

 

[HSTEd]

Would it be needed for Nuclear Flask trains from Sizewell, or from the now-closed Dungeness and Bradwell plants (assuming there is any nuclear flask traffic left?)

I'd be surprised if Sizewell is generating any significant flask traffic right now. Sizewell A closed a long time ago and Sizewell B is not exporting spent fuel - its being stored on site.

Dungeness B will soon complete defueling, if it hasn't already, and Bradwell closed a veerry long time ago.

 

[D365]

Is there a plan/list/timescale for freight ETCS Fitment publicly available anywhere? I'm not overly shocked more modern locos are jumping up in the queue but am slightly surprised, do DRS have much south of Peterborough that often?

Not in the public domain, and in any case it’s all in a state of flux (Network Rail CP7 among other factors).

 

[renegademaster]

(as the bulk of the liquid fuel distribution apparatus will have ceased to exist)

Considering that still, 99% of new HGVs are diesel, I think diesel at least has a few decades of being easily accessible and this is frankly bad hyperbole. I don't think any environmentalists have took aim at diesel freight in the Southeast which is a drop in the ocean of emissions reallt. In 20 years when 66s will be on their way out, batteries will probably be much better than they are now, and they'll probably be plenty of off the shelf battery locos from Europe rather than an expensive bespoke system that will only work in two corners of England.

 

[BerkshireRails]

Or DRS could take over with Class 88s, which are cleared without restriction
View attachment 187799
or fit monitoring gear to the passenger service fleet of 717s and avoid the need to run dedicated test paths, or have a bespoke monitoring regime by operatives instead of vehicles, or a combination of the above.

In the same doc it says Diesel is prohibited between Moorgate and Drayton Park, so I am not convinced that the 88s are permitted in the Northern City Line between Drayton Park and Moorgate.
I think it is a typo like with the 450s which according to the sectional appendix can't get to Reading as they can't travel between Reading Spur and Reading Southern Junctions which are required to access Reading from London via Wokingham.


A Class 450 at the Reading platforms only accessible from Reading Southern to Reading Spur Junction.

Section appendix map for approach into Reading Southern.

 

[zwk500]

In the same doc it says Diesel is prohibited between Moorgate and Drayton Park, so I am not convinced that the 88s are permitted in the Northern City Line between Drayton Park and Moorgate.

The clearance is stated in the Sectional Appendix, therefore it is permitted to be run.

I think it is a typo like with the 450s which according to the sectional appendix can't get to Reading as they can't travel between Reading Spur and Reading Southern Junctions which are required to access Reading from London via Wokingham.

It is possible to give additional clearance on a certificate that is not logged in the Sectional Appendix.

Having said both of those points, there are plenty of other clear mistakes in the Sectional Appendix so I wouldn't at all be surprised if somebody had accidentally put 'Y' down for the 88s between Drayton Park and Moorgate when it should be 'N'.

 

[Harlequinuk]

Why not have 3rd rail, just to charge batteries and not direct power requirements?

 

[HSTEd]

I'd posit a battery electric locomotive would be something resembling the JR Freight EH-800 [link is a picture]

~25m long with four two-axle bogies in a Bo-Bo+Bo-Bo layout. Say a 3.2MVA 25KV transformer (about 3 tonnes), four bogies with eight AGV-grade traction motors for about 6MW of continuous max power. You'd have a shore power hookup of some kind and a third rail pickup too.

If you went for a weight comparable to a Class 66, the eight evenly spread axles should allow a fairly low RA rating for the tractive effort. Could probably manage something like 50 tonnes of batteries without making it too heavy.
50 tonnes of last generation BYD blade batteries would be around 9MWh, more with more modern batteries.

The articulation would allow it to get close to a "go anywhere" loading gauge, and the two axle bogies would reduce track damage compared to three axle bogies.

Just a thought.

 

[zwk500]

The articulation would allow it to get close to a "go anywhere" loading gauge, and the two axle bogies would reduce track damage compared to three axle bogies.

Is there a need for a new third-rail loco to be go-anywhere? What would this capability cost over just being able to cover the existing freight routes, and what would the business justification for that cost be?

 

[HSTEd]

Is there a need for a new third-rail loco to be go-anywhere? What would this capability cost over just being able to cover the existing freight routes, and what would the business justification for that cost be?

There is a significant training and maintenance burden associated with multiple locomotive classes. A go-anywhere locomotive would allow the same pool of locomotives and drivers to cover all duties on the railway. The zoo of random locomotives hired in from spot hire companies etc would be jettisoned.

Given current trends, there are likely three duties 'pools' on the future railway: aggregates, containers and engineering/departmental trains. The latter is obviously not constrained to existing freight routes and a compact loading gauge is obviously an advantage there.
There probably isn't enough work on the railway to justify large (a la Class 66) production runs for multiple locomotive classes. Especially as more capable locomotives are able to move more freight with fewer units thanks to higher speeds and higher train weights (especially in aggregate)

The rising costs of labour and desire for ever higher availability also suggests we will want a low track damage potential, which militates against three axle bogies.

 

[zwk500]

There is a significant training burden associated with multiple locomotive classes. A go-anywhere locomotive would allow the same pool of locomotives and drivers to cover all duties on the railway. The zoo of random locomotives hired in from spot hire companies etc would be jettisoned.
Given current trends, there are likely three duties 'pools' on the future railway: aggregates, containers and engineering/departmental trains. The latter is obviously not constrained to existing freight routes and a compact loading gauge is obviously an advantage there.

Engineering/Departmental trains are not regular traffic though, and a lot of the more regular jobs (RHTT/Monitoring trains) could be done by things like the MPV or mounting equipment on the regular passenger fleet, if the locos were a problem. That would then leave aggregates haulage for possession work, which could be done simply at lower speed in areas of concern about clearances or bridge loadings (as Class 66s do already).

Aggregates and containers meanwhile will be on routes that can already take heavy loads because the cargo requires it.

Class 66s are Loco-Gauge compliant and RA7, and they don't seem to have a problem getting to 99% of the network.