Why were most multiple units 4 cars or less ?

[mike57]

The Brighton Belle units had 5 cars

I thought it did run as a ten car in regular service, I am sure I remember it seeing as 10 car growing up and I am sure there are pictures out there

 

[75A]

Yes, 2 five car units together with the other set at the Pullman shed in Brighton.
2 units togrther at busy times and one on it's own when it was quieter.

 

[cool110]

A train out of service for a straightforward defect, say one broken window which is out of stock, means, if it is a 2-car unit, you are 2 cars down. If it is a Thaneslink unit you are 12 cars down.

4 car (in 20m coach land) is a pretty sweet spot for London commuter EMUs. It's long enough to be a useful length on its own at quiet times, and gives three options for length on most routes, 8 for average loadings and 12 for particularly busy trains.

As very well demonstrated yesterday with LNW Crewe - Euston, first service booked as 12 but ran as 8 due to a fault on one of the units.

 

[norbitonflyer]

Sometimes it's for manoevring in depots as well - I understand the 701/0s are capable of being split in the middle as the wheel lathe at Wimbledon can't take a full ten-car train

 

[Southsider]

When it comes to the Strathclyde/former SPT electric network, the part of the network I'm most familar with, flexibilty, operational requirements, platform/carriage lengths and passenger demand varying dramatically throughout the day all factor into why it's been predominantly a 3-car EMU fleet - the 380s & 385s are the only permanent exceptions as far as EMUs go - since the introduction of the 303s, which directly replaced steam haulage on the North Clyde routes; DMUs (mostly 101s I think) had been running on the Cathcart Circle for a few years prior to electrification.

A mix of 3 & 6 car trains are the norm throughout the day on most of the network and has been for as long as I can personally remember, though single 3 car units can get pretty cosy during the peaks (speaking from extensive experience of a single 318 or 320 turning up on a evening peak Airdrie - Balloch service). Whether or not this norm will change when the 318s/320s come up for replacement remains to be seen.

There are/were exceptions to the 3/6-car rule, like 9-car trains on the Cathcart Circle on match days at Hampden (made up of three 303s/311s) and the 305s/322s (the former never worked a regularly scheduled passenger train in Strathclyde as far as I know, the latter had a token presence on Glasgow - Carstairs - Edinburgh - North Berwick services plus a one-off appearence on the Ayrshire Coast Line in 2010). 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).

Carriage length also comes into it, the headshunt at Neilston can’t cope with 6 car 380s.

 

[GatwickDepress]

4 car (in 20m coach land) is a pretty sweet spot for London commuter EMUs. It's long enough to be a useful length on its own at quiet times, and gives three options for length on most routes, 8 for average loadings and 12 for particularly busy trains.

Great sweet spot for portion working too The classic example being a 12 coach train from London Victoria splitting at Haywards Heath, 4 to Bognor and 8 to Eastbourne. 4 detach at Eastbourne and strengthen an up train whilst 4 continue on to Hastings. Very efficient, just as the Southern managers liked it.

 

[JonathanH]

Great sweet spot for portion working too The classic example being a 12 coach train from London Victoria splitting at Haywards Heath, 4 to Bognor and 8 to Eastbourne. 4 detach at Eastbourne and strengthen an up train whilst 4 continue on to Hastings. Very efficient, just as the Southern managers liked it.

Until the four coach trains became too short on the relevant portions. 8 from each side has brought many benefits while still retaining 4 for the journey east of Eastbourne.

 

[GatwickDepress]

Until the four coach trains became too short on the relevant portions. 8 from each side has brought many benefits while still retaining 4 for the journey east of Eastbourne.

True for now, but certainly not in the 80s and 90s. Loadings off-peak could be absolutely dismal.

 

[yorksrob]

True for now, but certainly not in the 80s and 90s. Loadings off-peak could be absolutely dismal.

I remember in NSE days when the London trains split at Eastbourne with the front four carriages continuing to Hastings. These were often quite busy at the time and I can remember thinking they ought to send eight carriages.

 

[Snow1964]

Quite so. Not sure what I was thinking there. Put it down to a senior moment!

The BEPs replaced the BIG's on the Pompey Fasts (81's) AFAIR, but it was a long time ago now, and can't remember the detail of why/when exactly.

I think there was something about the BIGs buffet cars, don't think it was asbestos related, but was the age of the kitchen equipment which wasn't repairable or didn't meet updated safety rules

Fairly sure those BEP units had a modification that was more field weakening on their motors, because they couldn't sustain line speed on the 1 in 80 gradients on Portsmouth direct, having been specified for flatter Kent lines.

But all rather a downgrade from 1937 sets, where 4RES sets 3054-3072 (19 units) had a kitchen car with a pantry, had 36 third class dining seats, and 12 first class dining seats in adjacent vehicle (the RES sets also had 5 first class compartments). But back then the Navy would expect it officers to eat properly at lunchtime when visiting London.

 

[Sun Chariot]

I think there was something about the BIGs buffet cars, don't think it was asbestos related, but was the age of the kitchen equipment which wasn't repairable or didn't meet updated safety rules

Interesting. I wonder what the Hastings DEMU preservation group has done within their former 4-BIG buffet second, to use it regularly on the tours. It was part of the 9 car (6 + 3) consist, on last Saturday's East West DEMU railtour.

 

[yorksrob]

I'm pretty sure the BIG buffet cars soldiered on on the central division long after the Portsmouth line got BEP's.

 

[The exile]

I'm pretty sure the BIG buffet cars soldiered on on the central division long after the Portsmouth line got BEP's.

Still operating on the Central division well into the 90s - though no doubt with a much reduced offering not requiring as much of the equipment.

 

[yorksrob]

Still operating on the Central division well into the 90s - though no doubt with a much reduced offering not requiring as much of the equipment.

I remember the local news showing some passengers organising a party in one of them in the 1990's !

 

[61653 HTAFC]

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.

Sprinters are a bit more efficient space-wise though- with the lack of a large guards van area found on the heritage units. Not to the extent that it completely negated the reduction in overall vehicles, but they were an improvement from that standpoint.
The "2 for 3" thing was applied to the fleet as a whole, not individual services. In many cases a service that previously used a 2-car first gen unit was still operated with a 2-car Sprinter or Pacer, so those services suffered no reduction in capacity and may have even gained capacity depending on the specifics of the vehicles used.
As an example, the Huddersfield to Sheffield service was solidly 2-car DMUs (c.18m cars but with a good ⅓ of one car taken up by the guard's van) until the second gen units started to come in. Initially 141s (with c.14m cars, no guard's van but narrow saloons with 2+2 bus benches) which may have been a slight reduction... but the later Pacers which were longer and wider quickly became the norm- although the 3-car 144s only became commonplace on the route after the Airedale and Wharfedale electrification freed them up.

 

[43096]

Fairly sure those BEP units had a modification that was more field weakening on their motors, because they couldn't sustain line speed on the 1 in 80 gradients on Portsmouth direct, having been specified for flatter Kent lines.

I would assume they had the same “greyhound” modifications that the CIGs in the 13xx series had (and which the BEPs worked with).

 

[Sun Chariot]

Sprinters are a bit more efficient space-wise though- with the lack of a large guards van area found on the heritage units.

When the 150/1 and 150/2 were introduced, I remember they had a lockable sliding door, into the saloon next to one cab; it was the area marked with a light blue cantrail stripe.
I only once saw the lockable area actually used - for a secure stowage of parcels.

 

[Helvellyn]

Shouldn't forget that some services went over to loco-haulage due to a shortage of DMUs. Something like Crewe-Derby operated with a Class 31 and four Mark 2s might have looked like a big loss of capacity when subsequently replaced by a 150/1 - but many of those loco hauled services were with declassified Mark 2 First Class coaches so it might have only provided seating for 157 people versus 140-150 in a two-car Sprinter.

 

[AM9]

There is another issue with EMU lengths on the busiest commuter lines, Where there are integrated fast and slow services, it has been common practice to lengthen the major stops served by all trains but leave the local train only stops at their previous length, e.g. on the GEML before the Lizzie opened, the major stations, Stratford, Shenfield and all of the stops to Southend Victoria the platforms are 240m, allowing 3x4 20m car trains, whereas the the 'metro' stations on the Electric line are shorter because they only had to accommodate the 3 x 306, 2 x 315 and 2 x 4-car outer suburbans on the Southend slows, all of which could manage with a 160m platform. By this measure, fast and slow outer suburban services coule be delivered by a single type of 4-car units (305/7 & 8 from the '60s and 321 from the late '80s).
A similar situation existed on the MML where Thameslink trains would be either a single or pair of 4-car class 319s. This allowed the use of the existing 'eight cer'length platforms. When the 'Thameslink Project' started, to cope with the much higher demand for capacity, some class 377 & 387 Electrostars were brought in allowing the longer distance fasts to be extended so one of the first tasks in the project was to lengthen the key stations on the line to cater for the 12-car fasts, West Hampstead, St Albans and beyond. Some of the metro stations were also extended to allow for flexibility during engineering possessions.

 

[driverd]

A train out of service for a straightforward defect, say one broken window which is out of stock, means, if it is a 2-car unit, you are 2 cars down. If it is a Thaneslink unit you are 12 cars down. Likewise if you want to reinforce a unit for extra demand, if 2-cars you can add another 2-car. For anything more than about 6 cars, you can't - you would need to run another train. So it doesn't happen.

I think, from a maintenance perspective atleast, fixed formation trains must be the biggest retrograde step in specifying modern MU trains.

The 700 example above really does demonstrate the major drawback of very fixed formations. Even with sprinters/pacers, a simple fault would result in the train being reduced by 1 vehicle (depending on the vehicle), a loss of capacity but no loss of a train. For example, it has been known for northern to form 1x 3 car 158 out of 2x 2 car units should 1 vehicle be out of traffic, or reduce a 3 car 144 to 2 if the middle vehicle is lost. Go further back and the hodge-podge mix of DMMU vehicles that could form a hybrid unit was almost endless.

I suspect the modern railway simply responds to cost - DfT stipulate bids to be bare minimum, TOCs bids to a price.

 

[YorksLad12]

For example, it has been known for northern to form 1x 3 car 158 out of 2x 2 car units should 1 vehicle be out of traffic, or reduce a 3 car 144 to 2 if the middle vehicle is lost. Go further back and the hodge-podge mix of DMMU vehicles that could form a hybrid unit was almost endless.

How do you connect your single 158 vehicle to the 2-car set? If you use the coupler on the cab end, how do you stop people walking out of the other end?

Am also moderately confident that the ten 3-car 144s never lost a centre car, even temporarily - unless you can cite otherwise?

 

[norbitonflyer]

How do you connect your single 158 vehicle to the 2-car set? If you use the coupler on the cab end, how do you stop people walking out of the other end?

You would always couple the extra vehicle to the two car set by its non-cab end (or, in some cases, in the middle of the unit), so that the resulting 3-car unit still has a cab at each end. If the cab in the middle of the unit has a gangway (as class 158s do), you open it up (isolating the driver's controls) as you would if you were coupling to another unit, and connect it to the (gangwayed) non-driving end of the adjacent carriage. Many 3-car 150s were created that way, by disbanding a 150/2 (with end gangways) and coupling each car in the middle of a 150/1, thus making two 3-car sets out of three two-car ones. (An adapter may have been needed to connect the driving end gangway to the intermediate one). Here is an example (note the driving cab at the near end of the middle car)

Note the yellow cab end on the middle car

If there was no gangway in the middle cab, (as in this 100/101 formation) the gangway from the adjacent carriage would be closed and locked.

This was also done on the Paddington suburban routes when a single unit (class 122) was deputising for a class 117 power car, as happened from time to time, the gangway from the trailer car in the middle of the unit being closed, thereby isolating it from the single unit's full width cab.

 

[Sun Chariot]

This was also done on the Paddington suburban routes when a single unit (class 122) was deputising for a class 117 power car, as happened from time to time

Indeed, I've a couple of 35mm shots of that formation. NSE's Thames Valley ones were 121s, rather than 122s.
Cracking photo of the Gloucester leading the MetCamm unit through Princes Street Gardens, by the way.

 

[norbitonflyer]

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

Judging by the position of the tail light, I think the train is actually travelling away from the photographer

 

[Sun Chariot]

Judging by the position of the tail light, I think the train is actually travelling away from the photographer

Oh yes - and it would be wrong line if it was leading!

 

[yorksrob]

I think, from a maintenance perspective atleast, fixed formation trains must be the biggest retrograde step in specifying modern MU trains.

The 700 example above really does demonstrate the major drawback of very fixed formations. Even with sprinters/pacers, a simple fault would result in the train being reduced by 1 vehicle (depending on the vehicle), a loss of capacity but no loss of a train. For example, it has been known for northern to form 1x 3 car 158 out of 2x 2 car units should 1 vehicle be out of traffic, or reduce a 3 car 144 to 2 if the middle vehicle is lost. Go further back and the hodge-podge mix of DMMU vehicles that could form a hybrid unit was almost endless.

I suspect the modern railway simply responds to cost - DfT stipulate bids to be bare minimum, TOCs bids to a price.

On the other hand, it does stop unscrupulous train operators squeezing everyone into four carriages to save costs !

Those long Thameslink ones are good people shifters.

 

[AM9]

I think, from a maintenance perspective atleast, fixed formation trains must be the biggest retrograde step in specifying modern MU trains.

The 700 example above really does demonstrate the major drawback of very fixed formations. Even with sprinters/pacers, a simple fault would result in the train being reduced by 1 vehicle (depending on the vehicle), a loss of capacity but no loss of a train. For example, it has been known for northern to form 1x 3 car 158 out of 2x 2 car units should 1 vehicle be out of traffic, or reduce a 3 car 144 to 2 if the middle vehicle is lost. Go further back and the hodge-podge mix of DMMU vehicles that could form a hybrid unit was almost endless.

I suspect the modern railway simply responds to cost - DfT stipulate bids to be bare minimum, TOCs bids to a price.

The 700s operate through what is probably the most intensively used pair of tracks on the mainline railway, that has the steepest gradients to boot. Consequently, they were specified with robust recovery features as blocking the core is operationally a critical.failire. The trains are traction-wise configured as two four-car or six-car units, and are rated such that each half-train unit has sufficient tractive effort to drag it's failed 'partner' up the 1:27 gradients out of the core to clear the core.
They also have safety doors to close off part of the train in the event of a fire or fumes.
In practice, as others have commented, they are amongst the most reliable units on the railway, although they may not be at the top of the list which treats a two-car unit the same as a 12-car one.

 

[Sad Sprinter]

DfT.
1. For example, Trans Pennine wanted some trains longer than 3 coach 185s, and more than were actually built. DfT cut back the proposed number ordered and blocked anything longer than 3 coaches. The depots such as Ardwick were then built to service 3 coach 185s, making it impractical for any future attempts to extend the number of coaches per unit.

2. When the 2nd generation dmus (Sprinters, Pacers) were built, it is understood that spending was authorised often on the basis of 2 new coaches to replace 3 old coaches. Sometimes the effect was even worse - Loco + 5 or 6 coach formation on Trans Pennine routes were replaced by 2 or 3 coach 158s...totally.insuffient to cater for passenger number growth created by more frequent services.

Re. Your first comment, it’s information like this that’s caused me to stay away from this forum these days but it makes me so angry. The malpractice in this country is genuinely disgusting.

 

[driverd]

How do you connect your single 158 vehicle to the 2-car set? If you use the coupler on the cab end, how do you stop people walking out of the other end?

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.

Am also moderately confident that the ten 3-car 144s never lost a centre car, even temporarily - unless you can cite otherwise?

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.

 

[61653 HTAFC]

When the 150/1 and 150/2 were introduced, I remember they had a lockable sliding door, into the saloon next to one cab; it was the area marked with a light blue cantrail stripe.
I only once saw the lockable area actually used - for a secure stowage of parcels.

I too remember those doors, never actually saw that section closed off to passengers though. I do recall seeing the shutters down on the parcel lockers on 156s, presumably because they were actually being used to carry parcels. The fact that the parcels provision on Sprinters could be used as regular seating (or luggage space in the case of the 156s) when not required for parcels was definitely an improvement on the older units- unless the service was really crowded and people were happy to cram themselves into the guards van!