Why are there no single or two-car EMUs?

Christmas

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Just as the title says, we have single and two-car diesels in the UK for quieter lines and off peak services but why not shorter electric trains? There must be countless electric services that operate around main lines that don't justify three-cars. Perhaps there are design limitations or maybe they'd be too expensive to design and build.
I'm referring specifically to 25kv pantograph trains.
 
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simple simon

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Such have existed - eg: in third rail days on the Tyneside Electrics, and also nowadays there were (still are?) some two coach EMU's on the Southern Electric - these are called Class 456.

I feel sure that one of the services these trains worked on was West Croydon - Wimbledon, which has now been replaced by single carriage rolling stock, albeit of a street-compatible format known as trams.

I suspect though that your question was really about heavy rail rolling stock - not light rail.
 
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43096

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Just as the title says, we have single and two-car diesels in the UK for quieter lines and off peak services but why not shorter electric trains? There must be countless electric services that operate around main lines that don't justify three-cars. Perhaps there are design limitations or maybe they'd be too expensive to design and build. Thoughts?
There’s two car units of Class 456 and 466.

Electrification has tended to be of the busiest lines, so shorter EMUs aren’t generally sufficient.
 

James James

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They exist in other countries, so there's certainly no technical reason you can't build them. In some countries, it was even common to have a powered single carriage, onto which further unpowered carriages would be attached (e.g. the RBE 540 in Switzerland, often operated as a pair sandwiching some conventional carriages, or even the NPZ although that one only has one cab and must operate together with a D[SF]O equivalent). They do certainly offer a bit more flexibility if you can rearrange trains as needed, but as we know that approach isn't in fashion (for good reason IMHO).
 

61653 HTAFC

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There were 2-car 309s in the past, which used to form 10-car sets on Clacton Express services formed of 1x 4-car, 1x 4-car with Griddle, 1x 2-car.

The two car units were later extended by inserting two former loco-hauled trailers in the middle. The former 2-cars were easily identifiable as they had the pantograph above one of the cabs.

Edit to add- the reason for the initial setup was to split to various Essex coast destinations. The two-cars usually went to Walton I think. When this mode of operation was shelved the 2-car units were extended to create a more uniform fleet.
 
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hwl

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Cabs cost a huge amount so a 2 car only costs 60-70% more than a theoretical 1 car just on the cab cost.

As MUs get longer you can have more shared equipment across vehicle (e.g. transformers compressors TCMS computers) so the cost per vehicle comes down.

e.g. LO Aventras (710 4/5 car) are effectively 30-35% more expensive than 9 car Crossrail Aventra
 

apk55

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What about class 399 Sheffield tram/train units? 37M long so similar to a 2 car unit and can work on 25KVac. However requires special low level platforms.
 

Bringback309s

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They exist in other countries, so there's certainly no technical reason you can't build them. In some countries, it was even common to have a powered single carriage, onto which further unpowered carriages would be attached (e.g. the RBE 540 in Switzerland, often operated as a pair sandwiching some conventional carriages, or even the NPZ although that one only has one cab and must operate together with a D[SF]O equivalent). They do certainly offer a bit more flexibility if you can rearrange trains as needed, but as we know that approach isn't in fashion (for good reason IMHO).
Other countries have been far more devoted to electrification with more investment in the infrastructure, environmental benefit and less concern over usage, unlike the good old UK that lets the infrastructure crumble and keeps re-upholstering seats, replacing perfectly acceptable rolling stock due to ridiculous legislation that benefits London and disadvantages the North, painting lampposts and filling the traveling publics heads with corporate clap-trap and propaganda about future investment and how great its "going to be" - but never actually is!
 

Harpers Tate

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Because you wouldn't electrify a line that only had demand sufficient for a single carriage train?
Doesn't always follow. Example: Doncaster <> Leeds = electrified as a "main line" but is also served by local stoppers that are 4 cars. Yet the equivalent (and partly shared) route to Sheffield, which has diesels because there are no wires after the routes diverge, yet has a similar demand profile, gets 2 or maybe occasionally 3 cars.
 

Grannyjoans

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Other countries have been far more devoted to electrification with more investment in the infrastructure, environmental benefit and less concern over usage, unlike the good old UK that lets the infrastructure crumble and keeps re-upholstering seats, replacing perfectly acceptable rolling stock due to ridiculous legislation that benefits London and disadvantages the North
Like 142's ?
 

edwin_m

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Because you wouldn't electrify a line that only had demand sufficient for a single carriage train?
Doesn't always follow. Example: Doncaster <> Leeds = electrified as a "main line" but is also served by local stoppers that are 4 cars. Yet the equivalent (and partly shared) route to Sheffield, which has diesels because there are no wires after the routes diverge, yet has a similar demand profile, gets 2 or maybe occasionally 3 cars.
But if the demand profile is similar then the train length should be similar as well. It's only getting shorter trains because DMUs are generally shorter and also scarce. So if it was electrified it would use EMUs of "normal" length, not short ones.

If the Felixstowe branch was electrified it might be an exception, as it would be done mainly for freight and until recently the passenger service was a single 153. However it is now a 755 unit, which would simply use electric power instead of diesel. Any shorter EMU would be a micro-fleet because no other electrified Anglia route has such low demand. Incidentally with three shortish passenger cars and a power car with no seating, is this variant of the 755 the shortest and/or the lowest capacity AC EMU?
 

Christmas

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Because you wouldn't electrify a line that only had demand sufficient for a single carriage train?
I'm not referring to lines that have been electrified to convert from diesels to electric. I'm referring to quieter services on existing lines that carry other services. But now that you mention it, outside of the peak the Paisley Canal line for example could be run with the electric equivalent of the Parry People Mover.
 

Harpers Tate

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...and conversely, where there is electrification (for, possibly, an unrelated operator, route pattern, reason, legacy, etc.) then "mysteriously" there are 4 cars rather than 2 or 3. Northern's brand new fleet comprises 3- and 4-car EMUs; and 2- and 3-car DMUs. Not necessarily because of some predicted demand profile; just because.....(what? - cheaper to build and run?) From the perspective of the user (who doesn't really care about the power source, but does care about overcrowding etc.) it doesn't seem rational.
 

big all

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MLV single vehicle 500hp should be faster than a 1000hp 4 car vep Brighton to London fast? Nope; a miserable 75-80mph at a push, compared to a VEP where 90+mph at 2 or 3 points

Why? Because the MLV has a cam shaft, so every time you lose power it takes 10-15 seconds to get back to full power. There are many gapes in the power supply, as many as 40 between London and Brighton, with every set of points, foot crossings, badger crossings etc, giving a great opportunity to save energy:frown:
 
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edwin_m

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I think the other person's point is that demand requires 2 cars but in places there is over-provision because there are no 2 car EMUs.
...and conversely, where there is electrification (for, possibly, an unrelated operator, route pattern, reason, legacy, etc.) then "mysteriously" there are 4 cars rather than 2 or 3. Northern's brand new fleet comprises 3- and 4-car EMUs; and 2- and 3-car DMUs. Not necessarily because of some predicted demand profile; just because.....(what? - cheaper to build and run?) From the perspective of the user (who doesn't really care about the power source, but does care about overcrowding etc.) it doesn't seem rational.
Are there many places where EMUs run largely empty even during peak hours (in "normal" times like we're not experiencing currently) so a shorter unit would be a better match to demand? I don't think that's the case on more than a handful of routes, which are rare enough and scattered enough that it wouldn't be worth building a microfleet of shorter units to operate them. Equally the routes electrified primarily for intercity operations tend to either carry well-patronized local/regional trains (Manchester southwards, ECML and WCML out of London) or not have them at all (Peterborough-Doncaster, Newcastle-Edinburgh). Most lightly-used stopping services on a main line were removed during the Beeching era to make room for the long-distance traffic.
 

Nick_C

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There were plenty of 2-car suburban third-rail EMUs - e.g. 2-BIL, 2-HAL and 2-EPB.

There still are some - the Isle of Wight class 483 units are 2-car.
 

mmh

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Are there many places where EMUs run largely empty even during peak hours (in "normal" times like we're not experiencing currently) so a shorter unit would be a better match to demand? I don't think that's the case on more than a handful of routes, which are rare enough and scattered enough that it wouldn't be worth building a microfleet of shorter units to operate them.
There are. Possibly the biggest example is Thameslink. Off peak there is massive over capacity on the south of London routes (I have no experience of north of St Pancras, so that may not be the case there!)

The argument for fixed formation, long trains was capacity and the operational inconvenience and inefficiency of splitting, so yes that was the view taken. Conversely though, short DMU fleets are ordered with the reasoning that they can be coupled for peak times, or to serve multiple destinations after splitting. Experience shows this rarely comes to fruition. One man's efficiency is another man's waste of resources, it seems.
 

pdeaves

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There were some single car third rail EMUs, the Gatwick luggage vans and things for taking boat trains to Folkestone(?). They were, however, not passenger carrying in their own right.
 

Alfie1014

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There were 2-car 309s in the past, which used to form 10-car sets on Clacton Express services formed of 1x 4-car, 1x 4-car with Griddle, 1x 2-car.

The two car units were later extended by inserting two former loco-hauled trailers in the middle. The former 2-cars were easily identifiable as they had the pantograph above one of the cabs.

Edit to add- the reason for the initial setup was to split to various Essex coast destinations. The two-cars usually went to Walton I think. When this mode of operation was shelved the 2-car units were extended to create a more uniform fleet.
Originally they worked 6 car to Clacton (griddle and 2car) and 4 to Walton.
2 cars operating on the own or multiple I believe were very rare, I only once saw a 2 car running as ECS up to Ilford. It might have been due to fact that the pantograph on these were at the leading end near the cab rather than contained within the set. Even until fairly recently paired 86s (or 90s) weren’t supposed to run in multiple on the GEML with the pans close together.
 

hexagon789

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There were 2-car 309s in the past, which used to form 10-car sets on Clacton Express services formed of 1x 4-car, 1x 4-car with Griddle, 1x 2-car.

The two car units were later extended by inserting two former loco-hauled trailers in the middle. The former 2-cars were easily identifiable as they had the pantograph above one of the cabs.

Edit to add- the reason for the initial setup was to split to various Essex coast destinations. The two-cars usually went to Walton I think. When this mode of operation was shelved the 2-car units were extended to create a more uniform fleet.
I think the units ran as buffet unit to Clacton, non-buffet unit to Walton and the two-car were meant to add capacity and boost performance in the peaks, hence being only two-car.
 

43096

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As above: Classes 456, 466, 483. And also the future Class 484 and former Class 482 (Waterloo and City LU stock).
The 482s may have nominally been 2-car units, but they don’t have a cab at one end so only ever operate as a 4-car pair of units.
 

rebmcr

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The lack of short EMUs is an additional barrier to electrification of the Marlow branch near Maidenhead. The pointwork at Bourne End's intermediate turnaround can't accommodate 3- or 4-carriages.
 

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