SWR Class 159 short formations

[ABDeltic]

In the last week there has been a huge increase in short formations on the West of England line. Today nearly all Exeter trains have been 3 cars West of Salisbury. The morning and evening peak has had a number of 3 and even 2 car trains to and from Waterloo. The reason has variously been given as 'a problem in the depot' or the generic 'more trains needing repairs at the same time', although today the SWR journey check doesn't seem to be giving any reason, just that train will be formed of 3 coaches. Does anyone know what is happening?

 

[weeklycommuter]

In the last week there has been a huge increase in short formations on the West of England line. Today nearly all Exeter trains have been 3 cars West of Salisbury. The morning and evening peak has had a number of 3 and even 2 car trains to and from Waterloo. The reason has variously been given as 'a problem in the depot' or the generic 'more trains needing repairs at the same time', although today the SWR journey check doesn't seem to be giving any reason, just that train will be formed of 3 coaches. Does anyone know what is happening?

The following is in Notes from South Western Railway on page 7 of the Salisbury to Exeter Rail User Group Newsletter No 23 24th July 2025 at the following link. Looks like SWR are often only able to provide one three car Class 159 set for the train services instead of the usual two sets to make a six car train.

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We have had issues with the reliability of the 15x fleet, though mainly the 159’s, over the last few weeks. This has been due, primarily with the engines, which has also affected other TOC’s eg GWR,. The engines are failing, sometimes catastrophically, earlier than they should. Whilst we would normally have a rolling supply of engines, ”off the shelf”, the rate of failure has often exceeded the supply form the manufacturers. There is now only one supplier in the UK which refurbishes these engines of this type for all TOC’s. We are working closely with them to urgently improve the engine reliability and supply of replacements.

 

[ABDeltic]

The following is in Notes from South Western Railway on page 7 of the Salisbury to Exeter Rail User Group Newsletter No 23 24th July 2025 at the following link. Looks like SWR are often only available to provide one three car Class 159 set for the train services instead of the usual two sets to make a six car train.

Thanks, that's very helpful. What with the Crewkerne stops and now the announcement of a reduced service west of Yeovil from August 11th, the line is in a bad way at the moment.

 

[Nimbus020]

Thanks, that's very helpful. What with the Crewkerne stops and now the announcement of a reduced service west of Yeovil from August 11th, the line is in a bad way at the moment.

Hi all - very timely - I witnessed the 10:27 departure from Clapham Jct (going to Exeter) on Fri 1 Aug formed of only a single 3-car unit. To say the train was ‘rammed’ would be a serious understatement! - I felt especially sorry for families with suitcases who had to somehow squeeze on (standing room only). I mentioned it to the guard standing on the platform & she seemed pretty embarrassed about the whole situation. New ‘boss’ Laurence Bowman has a lot to sort out on SWR - can only wish him luck!

 

[gabrielhj07]

Looks like I've been rather lucky that my somewhat regular 1L60 trips have been 6/8 carriages. Most up trains are busy throughout the day, even with 6 carriages, and it can sometimes be a struggle to board at stations East of Yeovil Junction.

 

[Kite159]

Guards can only do so much in requesting the likes of Woking & Basingstoke are made pick up only calls by not advertising the stops (Woking has plenty of services, the only downside is the Weymouth train at XX;35 skipping Clapham & Basingstoke which puts extra pressure on the diesels.

Frees up space for those heading further west

 

[Towers]

Interesting. I wonder is this a case of certain batches of engines being specifically affected and therefore grounding particular units?

 

[Big Jumby 74]

Woking has plenty of services

Between Waterloo and Woking perhaps, but no more than any other station (on WoE services) in the Down direction. No one at Woking or Basingstoke with their luggage in many cases and heading to Andover or West of, wants to be changing trains any more than I would.

 

[gabrielhj07]

Certain peak down WoE trains are pick up only at Woking, it could be an idea to extend this to all of them?

 

[pompeyfan]

There’s been quite a few occasions of Woking and Basingstoke being made pick up only on down WoE services with the extra stops being put on the 1Wxx

 

[Clarence Yard]

Interesting. I wonder is this a case of certain batches of engines being specifically affected and therefore grounding particular units?

You usually monitor these kind of problems by regular oil sampling and analysis. No need to ground a unit until it is in danger of catastrophic failure.

 

[Towers]

You usually monitor these kind of problems by regular oil sampling and analysis. No need to ground a unit until it is in danger of catastrophic failure.

That makes it odd then to be short forming so many services, no? Surely just keep them running, with an engine isolated if need be, unless they’re critical?

I wonder if we might see the Romsey rounders being reduced or bustituted to free up a couple of sets if things get desperate?

 

[Clarence Yard]

Some units have got to the stage where they can’t safely be run. The supply chain has also been severely disrupted because of this issue so there is a real shortage for 158/9 operators.

 

[ABDeltic]

Some units have got to the stage where they can’t safely be run. The supply chain has also been severely disrupted because of this issue so there is a real shortage for 158/9 operators.

Not got any inside information but there are 7 or 8 159/0 that haven't been out for about 10 days. Not sure abou the 159/1. I wonder if formations will improve next week with the reduced service west of Salisbury, though schedules are longer.

 

[Towers]

Surprisingly (or not!) high number of 15x sat on Salisbury depot this lunchtime; presumably some of them are dead?

Any evidence of disruption at GWR or elsewhere as a result of this?

 

[computerSaysNo]

I live near a depot for another TOC and it seems to be common for 158s and 170s to be parked up overnight and their engines left running the whole night. I wonder if these additional hours and long unbroken durations at idle has an especially detrimental effect on the engines?

 

[Towers]

I live near a depot for another TOC and it seems to be common for 158s and 170s to be parked up overnight and their engines left running the whole night. I wonder if these additional hours and long unbroken durations at idle has an especially detrimental effect on the engines?

I thought those practices disappeared with BR in the 90s! There should be no need for that, unless the trains are being shunted around all night etc.

 

[Deepgreen]

I live near a depot for another TOC and it seems to be common for 158s and 170s to be parked up overnight and their engines left running the whole night. I wonder if these additional hours and long unbroken durations at idle has an especially detrimental effect on the engines?

I can't think of any reason to run engines continuously like that - waste of fuel, with needless pollution, noise and wear and tear. If there IS an engineering reason for this otherwise terrible practice, I'd be fascinated to hear it.

 

[Towers]

I can't think of any reason to run engines continuously like that - waste of fuel, with needless pollution, noise and wear and tear. If there IS an engineering reason for this otherwise terrible practice, I'd be fascinated to hear it.

Traditionally it’s always been the fear that if you switch them off they won’t start again! Perhaps the TOC in question are short of decent batteries!

 

[Nimbus020]

One interesting topic is that I understand that Stagecoach’s aborted 2017 franchise re-bid included Stadler ‘Flirt’-based bi-mode units to replace the 159s/158s - have to confirm this though

 

[Deepgreen]

Traditionally it’s always been the fear that if you switch them off they won’t start again! Perhaps the TOC in question are short of decent batteries!

Yes, I considered that 'reason' too - in 2025 that is a pathetic excuse!

 

[computerSaysNo]

I thought those practices disappeared with BR in the 90s! There should be no need for that, unless the trains are being shunted around all night etc.

I did wonder if that was the reason, if they were going to be shunting them around all night. But then I'd expect a modern business to be shutting down all but one engine per consist as they won't need the full power for shunting around at 5mph.

I can't think of any reason to run engines continuously like that - waste of fuel, with needless pollution, noise and wear and tear. If there IS an engineering reason for this otherwise terrible practice, I'd be fascinated to hear it.

I did make an initial enquiry to the TOC (or Network Rail, it was a while ago so I can't quite remember) going down the noise and pollution route, but they wanted my name and address before anything else and I didn't want to risk making my landlord angry if anything went back to them, so I didn't take it any further.

Traditionally it’s always been the fear that if you switch them off they won’t start again! Perhaps the TOC in question are short of decent batteries!

Maybe. I'd have thought installing shore power to keep the batteries topped up would be cheaper long term than running the engines, but this is a TOC we're talking about so they'd never do anything sensible like that!
I also had the idea that they could install shore compressed air too, as a fixed mains-powered air compressor can't be that expensive, and it would let them fully shut down the trains but still be able to move them at short notice. But again, when do TOCs do anything sensible like that.

 

[Ianigsy]

This seems to have been going on for a while now - at the beginning of July I caught the 1550 Waterloo-Yeovil Junction as far as Salisbury as one leg of a journey to Bristol, to find that it was short formed (158 as against 158+ 3 car 159). Snug, and I don’t think everybody was seated until Andover, but as has been noted, there seemed to be a fair few units on shed at Salisbury. Not really being familiar with the amount of unit shuffling that goes on at Salisbury I don't know how normal that is.

Mind you, to my Northern eyes, I think the 9-car 159 formation I saw at Salisbury looked like sheer luxury!

 

[moley]

I'm really surprised that we're not seeing the WOE service restricted to south of Basingstoke. I acknowledge that it requires a change of train for WOE travellers however it is a same platform change.

With unit issues and line issues, this would seem sensible to maintain reliability of timetable.

 

[Big Jumby 74]

With unit issues and line issues, this would seem sensible to maintain reliability of timetable.

Understandable thinking indeed. Would likely mean TT changes (to 1Wxx) at Basingstoke and Woking to provide connections, which perhaps in itself does not amount to a great deal, but then one has to consider capacity (bums on seats - or not - as in having to stand!) East of Basingstoke etc.
Schedule wise it would take some risk out of the overall TT East of Basingstoke (Up trains mainly) if Up WoE services were regularly presenting across Worting Jn late, but as those services are very largely self contained (unit and crew wise), return down services would normally recover any lost time on the previous Up journey during the layover at Waterloo.
The one potential benefit (to the WoE itself) might be that terminating/restarting at Basingstoke, this should throw up (off top of my head) in theory 3 sets of stock, allowing for a robust (40 ish mins) turn round at Basingstoke, thus helping out any stock shortage and allowing for late running on the UP to some degree.

 

[LowLevel]

If they're anything like anywhere else they're probably short of round wheels.

 

[Taunton]

Traditionally it’s always been the fear that if you switch them off they won’t start again! Perhaps the TOC in question are short of decent batteries!

That's how it long used to be in places with cold climates (Canada, Russia etc) in winter. Batteries deteriorating are part of it, along with engine injectors, fuel spec changes (for supposed green-ness), and even a fitter economised and no longer on shift at 5am to deal with non-starters.

Can you bump-start modern diesels by other cars in the formation getting them rolling? You could certainly do that with Modernisation Plan 'Blue Square' units, sometimes needed at every stop where one of the engines shut down.

 

[Craig1122]

Sad to see the slow decline of this line compared to how the service was continually enhanced during the earlier SWT days. The west country really does deserve better.

 

[Clarence Yard]

Maybe. I'd have thought installing shore power to keep the batteries topped up would be cheaper long term than running the engines, but this is a TOC we're talking about so they'd never do anything sensible like that!
I also had the idea that they could install shore compressed air too, as a fixed mains-powered air compressor can't be that expensive, and it would let them fully shut down the trains but still be able to move them at short notice. But again, when do TOCs do anything sensible like that.

Shore supply of any description is hideously expensive to put in (it always has been, even in BR days) and, in any case, useless for 15x and 16x stock as they are not bus wired to support shore supply. Each power car is effectively its own system. What you usually do is connect each car up to battery chargers which are usually fed by charging points down each walkway, if the sidings are so fitted.

When you have a fleet that wanders, you do need to pay particular attention to battery maintenance at home depot because the starting load on the batteries is onerous and they won’t last unless you keep them in good condition. Jump starting a 15x or 16x like a mechanical DMU is not possible.

I know, in some places, units at outstations are left running for cleaning purposes but in this day and age there isn’t any other good reason, once the necessary overnight shunting has taken place.

 

[computerSaysNo]

Shore supply of any description is hideously expensive to put in (it always has been, even in BR days)

Why?

and, in any case, useless for 15x and 16x stock as they are not bus wired to support shore supply. Each power car is effectively its own system. What you usually do is connect each car up to battery chargers which are usually fed by charging points down each walkway, if the sidings are so fitted.

Ah. So you couldn't even shut down all but one engine then as the remaining engine wouldn't charge the batteries in the other carriages?

When you have a fleet that wanders, you do need to pay particular attention to battery maintenance at home depot because the starting load on the batteries is onerous and they won’t last unless you keep them in good condition. Jump starting a 15x or 16x like a mechanical DMU is not possible.

Jump as in connecting the low/dead battery to a healthy/live one? Why isn't this possible?
I can see that what I'd call bump starting wouldn't work as the fluid clutch would automatically be engaged while the train speed is higher than the engine speed so the engine would never actually turn. Would this not have been the case for mechanical DMUs too? Bump starting relies on the engine being able to provide a braking force to the train and I thought even mechanical DMU gearboxes had a sort of clutch which automatically cut the engine/wheel connection at throttle notch 0? Otherwise if you accelerate in gear 1 then cut the power and switch to gear 4 to coast as per the operating instructions, the engine would stall?
Maybe I'm overcomplicating it?