Why were most multiple units 4 cars or less ?

[norbitonflyer]

Is tghere actually a difference between the inter-car gangways on a 15x and the end gangways at the driving ends, or can they be coupled connected without any modification?

The Edinburgh-Glasgow Inter city sets (Class 126) 3-car sets were gangwayed at one end only, so when two units were coupled together by their gangwayed ends they could run as a six car through-gangwayed unit. However, in most photgraphs I have seen they were formed with the gangwayed driving cars as cars 2 and 5, not 3 and 4, meaning the driving end gangways were each coupled to the inner gangway of the adjacent driving motor car.

See here (note the yellow end of the second car in the train)

 

[Taunton]

Cracking photo of the Gloucester leading the MetCamm unit through Princes Street Gardens, by the way.

That's actually how many were in Central Scotland at that time, long term; when the dmu requirement was reduced, particularly when the 1974 WCML electrification came along to outer Glasgow services, the Gloucester and Cravens 2-car units were split up, the driving trailers withdrawn, and the power cars added to the more serviceable Met-Can 2-car units to make them 3 cars. Part of this was 2-car dmus were then banned from Glasgow Queen Street, due to their poor performance on the steep climb outwards to Cowlairs, and complete disruption caused if one of their two engines was out of action. Apart from these, there were all sorts of other mixed formations around.

 

[61653 HTAFC]

The most prominent case to come to mind was the Calder valley fire unit. The middle vehicle was heavily fire damaged around 2010ish (not sure on the exact year), for a good year or so, that unit was running around as a 2 car.

IIRC that was the only example of the casualty vehicle being conveniently the one without a cab. The only other times that the 3-car sets ran as 2-cars, were (a) when brand new, the MS vehicles were delivered a few weeks later; and (b) when the units were refurbished and had the bus seats replaced by high-backed ones, the funding for the MS vehicles were from a different source as they were owned by WYPTE at the time. For a brief period the units ran with refurbished end cars and an unrefurbished middle car. Once the contracts were signed to refurbish the middle cars, each unit ran as a 2-car set while its MS went through the works.

 

[Taunton]

The Edinburgh-Glasgow Inter city sets (Class 126) 3-car sets were gangwayed at one end only, so when two units were coupled together by their gangwayed ends they could run as a six car through-gangwayed unit. However, in most photgraphs I have seen they were formed with the gangwayed driving cars as cars 2 and 5, not 3 and 4, meaning the driving end gangways were each coupled to the inner gangway of the adjacent driving motor car.

See here (note the yellow end of the second car in the train)

This is actually how they were officially formed, as effectively fixed formation 6-car units, although their dedicated depot at Leith treated them as individual vehicles to be shunted around; a small number also ran as 3-car sets, with either power car type leading, on lesser services. It was the inspiration for the Trans Pennine 6-car units, same formation arrangement from same builder, which followed a few years later. It allowed the refreshment car to be in the centre of the train, and the first class accommodation in the trailers to be formed together.

 

[43096]

Is tghere actually a difference between the inter-car gangways on a 15x and the end gangways at the driving ends, or can they be coupled connected without any modification?

On Class 150-156 the outer and inner end gangways are compatible, but on a 158/159 the inner end gangways are wider than the cab end gangways, so adapter plates are used where hybrid formations have been made up.

 

[Sun Chariot]

On Class 150-156 the outer and inner end gangways are compatible, but on a 158/159 the inner end gangways are wider than the cab end gangways, so adapter plates are used where hybrid formations have been made up.

I never knew that, that's intriguing. In which case the adaptor plates must've been used during the short period early in the 1990s when temporary formed with one 158 vehicle plus one 156 vehicle. Or, were the inner 158 gangways the same width as the 156 inner gangways?

 

[YorksLad12]

As per the next post. Under serco/abellio I can remember a 158 3 car (formed of 1.5x perking enginged 158 vehicles) and 2 occasions of a 150 3 car unit. All lasted a few months whilst the other half of one unit was sorted. I can't remember any numbers but it would have been circa 2014-2015.

Further back still, arriva trains northern would often sub a 153 for half of a 156, there's quite a few pictures of this formation floating around.



The most prominent case to come to mind was the Calder valley fire unit. The middle vehicle was heavily fire damaged around 2010ish (not sure on the exact year), for a good year or so, that unit was running around as a 2 car.

IIRC that was the only example of the casualty vehicle being conveniently the one without a cab. The only other times that the 3-car sets ran as 2-cars, were (a) when brand new, the MS vehicles were delivered a few weeks later; and (b) when the units were refurbished and had the bus seats replaced by high-backed ones, the funding for the MS vehicles were from a different source as they were owned by WYPTE at the time. For a brief period the units ran with refurbished end cars and an unrefurbished middle car. Once the contracts were signed to refurbish the middle cars, each unit ran as a 2-car set while its MS went through the works.

All new/news to me. The closest I've come to is 3x153 (of which I have a photo, somewhere).

 

[43096]

I never knew that, that's intriguing. In which case the adaptor plates must've been used during the short period early in the 1990s when temporary formed with one 158 vehicle plus one 156 vehicle. Or, were the inner 158 gangways the same width as the 156 inner gangways?

AIUI that was when the adapter plates were first (hastily) designed and manufactured.

 

[Pigeon]

What you're describing is the effect; the policy on replacement of first generation dmus was Treasury driven and basically said 3 old cars should be replaced by 2 new ones. This was justified on the grounds that BR as a whole lost money and Other Provincial Services, which relied very much on dmus, lost more than any other part of the railway. Since dmus longer than 3-cars were nearly all on metro suburban routes it was inevitable that the new regional fleet would be dominated by 2-car units.

It was extremely unfortunate that this thinking prevailed at the point at which BR had just about stopped the decline in passenger numbers meaning it was ready to start expanding timetables on key inter-urban routes. Given the higher profile of these services it was no surprise that the new Sprinters were put on them regardless of whether they were really suitable. No wonder that overcrowding soon became commonplace, the overall passenger fleet simply wasn't big enough.

It was worse than that, it was rotten from the start. Very many DMU routes around Birmingham were operated with 3-car sets and they could get pretty full at times. So when those 3-car sets, especially those with high-density seating, were replaced with 2-car 150s with their ruddy awful seating layout and huge seatless gaps for doors, the 150s had too many people on them right from the start with the same passenger numbers as before.

 

[Shaw S Hunter]

It was worse than that, it was rotten from the start. Very many DMU routes around Birmingham were operated with 3-car sets and they could get pretty full at times. So when those 3-car sets, especially those with high-density seating, were replaced with 2-car 150s with their ruddy awful seating layout and huge seatless gaps for doors, the 150s had too many people on them right from the start with the same passenger numbers as before.

It's notable that WMPTE was the only English PTE that didn't help finance some Pacers to top up the local fleet. On the one hand that meant "West Midlanders" were spared the Pacer Experience, on the other a lack of Pacers in the other PTE areas hardly bears thinking about in terms of over-crowding.

 

[driverd]

It was worse than that, it was rotten from the start. Very many DMU routes around Birmingham were operated with 3-car sets and they could get pretty full at times. So when those 3-car sets, especially those with high-density seating, were replaced with 2-car 150s with their ruddy awful seating layout and huge seatless gaps for doors, the 150s had too many people on them right from the start with the same passenger numbers as before.

Out of interest, given these were clearly routes carrying lots of people and, I presume, not financial basket cases, why did BR dampen demand with tiny trains?

 

[norbitonflyer]

Out of interest, given these were clearly routes carrying lots of people and, I presume, not financial basket cases, why did BR dampen demand with tiny trains?

They were,'t intereted in inctreasing revenue, just reducing costs. And like most suburban routes, the peak hour commuter traffic, which determines the fleet size, is a captive market, so demand won't be dampened by making the journey less pleasant.

 

[Bill57p9]

There's also the 7-car trains that run on the Ayrshire Coast (mainly to Ayr, 7 coaches are about as much as can fit into Ayr's bay platforms both from a physical and signalling standpoint).

Splitting hairs slightly, Ayr bay platforms can only accommodate 4 cars. 7 coach trains use one of the two through platforms. I have been told by a planner that the signalling sections on the through platforms can accommodate 7 car trains but not 8 and this is why 7 rather than 8 car formations are used on the Ayrshire coast.

 

[Fleetwood Boy]

Splitting hairs slightly, Ayr bay platforms can only accommodate 4 cars. 7 coach trains use one of the two through platforms. I have been told by a planner that the signalling sections on the through platforms can accommodate 7 car trains but not 8 and this is why 7 rather than 8 car formations are used on the Ayrshire coast.

That’s interesting. I’ve definitely seen an 8-car train for Ayr, I assumed as a one-off due to failure of a 380/0, wonder how they dealt with that.

Is that why 385s don’t go to Ayr?

 

[Bill57p9]

That’s interesting. I’ve definitely seen an 8-car train for Ayr, I assumed as a one-off due to failure of a 380/0, wonder how they dealt with that.

Is that why 385s don’t go to Ayr?

What I was told was that taking an 8 car into Ayr isn't impossible but blocks multiple track circuits, hence the very strong preference for 7 car.

No inside info on the 385s, however they were procured for the central belt rather than Ayrshire Coast. TBH I prefer the 380 seats over 385 so am quite happy with this distribution!

 

[Strathclyder]

Splitting hairs slightly, Ayr bay platforms can only accommodate 4 cars. 7 coach trains use one of the two through platforms. I have been told by a planner that the signalling sections on the through platforms can accommodate 7 car trains but not 8 and this is why 7 rather than 8 car formations are used on the Ayrshire coast.

How I got the bay and through platforms confused I'll never know. Major brain fart there lol

But yes, you're entirely correct.

 

[Sun Chariot]

Post #52 includes an image of a Gloucester class 100 DMBS vehicle attached to the rear of a Metro Camm class 101 unit. Thereby isolating the 100 DMBS passengers from accessing the 101's toilet facilities...

I found a similar scenario on the excellent Railcar site: here's a Pressed Steel class 121 DTS vehicle, attached to the front of a Swindon class 120 unit (running as a power-twin).

Class 121 DMU at Church Stretton

The history of Diesel Multiple Units (DMUs / railcars) in Britain.

railcar.co.uk

I only ever saw one class 121 DTS in service; I always thought them a bit of an oddity, as their operation was reliant on being attached to powered DMU vehicle(s) - and, lacking a gangway, their passengers would need tight bladders...

 

[Mat17]

For a brief period the units ran with refurbished end cars and an unrefurbished middle car. Once the contracts were signed to refurbish the middle cars, each unit ran as a 2-car set while its MS went through the works.

I remember this, some of the three cars were definitely reduced to two car trains for a spell. I even travelled on one.

 

[Taunton]

Post #52 includes an image of a Gloucester class 100 DMBS vehicle attached to the rear of a Metro Camm class 101 unit. Thereby isolating the 100 DMBS passengers from accessing the 101's toilet facilities...

I found a similar scenario on the excellent Railcar site: here's a Pressed Steel class 121 DTS vehicle, attached to the front of a Swindon class 120 unit (running as a power-twin).

Class 121 DMU at Church Stretton

The history of Diesel Multiple Units (DMUs / railcars) in Britain.

railcar.co.uk

I only ever saw one class 121 DTS in service; I always thought them a bit of an oddity, as their operation was reliant on being attached to powered DMU vehicle(s) - and, lacking a gangway, their passengers would need tight bladders...

There weren't toilets in any of the WR "Suburban" units, so no change there. Nor were there any gangways between any of such cars. And every driving trailer on BR needed a power car attached. Having said that, I never, ever, saw one of the WR independent driving trailers in use.

There was a considerable upset when the WR took over the Southern west of Salisbury, previously fully steam with main line hauled stock. This was dieselised with a motley group of spare stock from elsewhere, in particular Suburban units from South Wales. No toilets, and they were used on some lengthy runs, such as Salisbury to Ilfracombe. After articles in the local press, the complaints went up from the area MPs to the Minister of Transport, to the BR Chairman, and thence to Paddington, with an instruction to "do something".

There were nine Suburban 3-car units, and also nine of the last batch of Cross-Country units, which had two of their three cars with toilets. So one weekend the trailers of all were exchanged, giving one toilet per set. As the Suburban units had no gangways there was now no communication anywhere within the sets, but at least if you needed the facility it was there. The sets now all looked ridiculous, as the body profiles were different and the wasted gangways just hung loose. Furthermore it was just at the transition from green livery to blue, or in the case of Cross-country units to blue/grey. Several of the sets had all three cars in different colours. One got the impression the whole thing had been done grumpily and under duress by the staff. Lasted for a few years (there are various photos around) until services were further reduced or closed, and the sets were put back as they were.

Meanwhile, Suburban 3-car sets with no toilets or gangways turned out most days on Bristol to Weymouth and back throughout the whole lifetime of these sets.

 

[Sun Chariot]

Indeed @Taunton hence my surprise at the linked example being used on a Cardiff - Shrewsbury service.
That's why I thought the 121 DTS a bit of an oddity: at best, it's paired with a Driving Motor, or a power twin. At worst, it gets put on a power-trailer pair - creating an underpowered consist.

NSE's class 121 DTS examples were generally for Thames Valley services. I took one from Bicester Town to Reading. L210, L211 and L283 seemed to roam around that sphere, plus the Marlow / Windsor shuttles.
I didn't see any DTS examples attached on class 117s into Paddington; only the DMBS bubble cars. However, Railcar's site comes up trumps, a 117 set plus 121 DTS:

Class 121 DMU at Iver

The history of Diesel Multiple Units (DMUs / railcars) in Britain.

railcar.co.uk

 

[Peter Mugridge]

There weren't toilets in any of the WR "Suburban" units, so no change there.

The centre carriages on the 117s had toilets didn't they?

Albeit yes, no gangways so the passengers in the driving carriages couldn't use them.

 

[Sun Chariot]

The centre carriages on the 117s had toilets didn't they?

Yes, they did @Peter Mugridge . A photo's linked in post #80.
Ditto class 118s which I saw around Exeter in the 1980s.
The class 116s used in South Wales were completely lavless though.

 

[norbitonflyer]

Yes, they did @Peter Mugridge . A photo's linked in post #80.
Ditto class 118s which I saw around Exeter in the 1980s.
The class 116s used in South Wales were completely lavless though.

Checking Longworth - of the suburban DMUs
115s and 127s had one trailer with a lav and one without
116s and 125s had no lavs. Nor did the single units.
117s and 118s had a lav in the trailer

== Doublepost prevention - post automatically merged: 20 Apr 2025 ==

I didn't see any DTS examples attached on class 117s into Paddington; only the DMBS bubble cars. However, Railcar's site comes up trumps, a 117 set plus 121 DTS:

Class 121 DMU at Iver

The history of Diesel Multiple Units (DMUs / railcars) in Britain.

railcar.co.uk

That formation (DMBS/TC/DMBS/DTS) is of course no worse underpowered than a DMBS/DTS pair

I think I recall a 3-car set made up of a class 117 DMS coupled to a 121 DMBS/DTS pair.

I can also claim haulage by a 128, coupled to a class 117 3-car set

 

[Sun Chariot]

That formation (DMBS/TC/DMBS/DTS) is of course no worse underpowered than a DMBS/DTS pair

I think I recall a 3-car set made up of a class 117 DMS coupled to a 121 DMBS/DTS pair.

I can also claim haulage by a 128, coupled to a class 117 3-car set

In reverse order....

You get bonus points if you snuck into the 128 DPU instead of the 117's passenger saloons.

Yes, I have a shot of (IIRC) L404 which substituted the 117's DMBS with a 121 DMBS. And a photo of the wonderful L408: a 104+101+117 set. The 104 DMBS drowned out everything in its vicinity.

Yes, NSE Thames Trains and Chiltern Trains pools- typically - ran with 50% power cars (Thames' L2xx sets, Chiltern's 115 quads and 115+108 power-trailer pairs); or with 67% power cars (Thames 101 L8xx, 117 L4xx 3-car sets).
The Gospel Oak Barking 104 power twins, I recall, were not part of the Thames Trains pool.

 

[MarlowDonkey]

I didn't see any DTS examples attached on class 117s into Paddington; only the DMBS bubble cars. However, Railcar's site comes up trumps, a 117 set plus 121 DTS:

In the 1970s the through morning trains from Bourne End to Paddington were regularly 7 cars, being 2 normal 117 sets plus the unpowered trailer. Four coach formations were a rarity though. They were allowed to run non-stop from Maidenhead or Burnham to Paddington despite their 70 mph top speed potentially getting in the way of HSTs.

London area 117 sets had gangways inside the set from the early 1970s. This gave access to the toilets in the middle trailer as well as allowing a conductor to inspect or sell tickets without leaving the train.

The other use of the unpowered trailers was with a bubble car on branch lines.