How long can a train be before it's too long?

[KingDaveRa]

Driving home the other day, I saw a Chiltern train go whizzing by (on the Chiltern Mainline), and observed it was made up of three three-car 168s - a total of 9 vehicles. I was amazed just how long it was, and I don't recall ever seeing one of Chiltern's trains being this long - not a DMU at least.

But it made me wonder, is there a limit to how long a train can be? Obviously there's the ludicrously long freight trains in other countries, but surely there's limits to passenger trains? Or aren't there, and it's just limited by available stock?

 

[Clip]

I guess you can make a train as long as you want it - Just look at the Aussie ore trains - but with longer trains you need longer platforms and we simply cant have many of them in our cities which makes longer ones no good as even with SDO the dwell time would probably be longer as folk moved down inside the carriage

 

[Dr Hoo]

The Indian Pacific train across Australia typically loads at 25 coaches plus two car-carrying wagons.

 

[big all]

dozens off limiting factors really
you could run a say 30 coach train on most main lines but only between say 8 to 12 coaches in the main platforms but reduced by say 2 locos within the starter signals further locking up the whole points and crossing at the rear
it used to be 14-16 coach length at major stations to allow a say 12-13 coach train and turnover engine at the other end

 

[tbtc]

The Caledonian Sleeper is about as long as it gets nowadays (sixteen coaches, or is it fifteen plus loco, I can't remember - the Sleeper is designed for comfort rather than speed though - no need for breakneck pace to get to London/ Scotland at four in the morning - the idea is to arrive at an appropriate time for waking up, so it doesn't have to go at Pendolino speeds, and is free to drain plenty of juice as there aren't many other services around at that time of day).

But a lot of the problems with train length come down to:

• Platform length (not just the termini but also intermediate stations - I can maybe accept an SDO situation where there's one carriage hanging off the edge of the platform but if you are expecting passengers to walk more than one carriage length to get off at an intermediate station then you may need some hefty dwell times to be on the safe side)
• Fouling junctions (or taking longer to clear junctions)
• Electricity issues (for AC/ DC services, there may be a limit to the power that one train can drain from the juice)
• Locomotive issues (fine on a nine coach DMU, where each carriage has an engine but if the rule of thumb is that longer trains justify loco hauled then there's limits to just how much one loco can haul... you could add a second loco of course but then that lengthens the train even further

As an example, look at the old Southern Region, where they could certainly do with longer trains on a number of services but have maxed out at 12x20m trains (or 10x23m) - to go any longer would mean redesigning several stations/ junctions etc and beefing up power supplies

 

[PeterC]

Are there limits on the number of multiple units that can be coupled together? I have a, possibly faulty, recollection that some classes back in the 60s and 70s were restricted to three.

 

[AndrewE]

To answer the original question: If you can't get to the front (or to your reserved seat, or a to relatively quiet coach) between the barrier being opened at Euston and the train's departure! However that's more to do with the departure board and too-tight turn-rounds than the length of the trains.

 

[big all]

Are there limits on the number of multiple units that can be coupled together? I have a, possibly faulty, recollection that some classes back in the 60s and 70s were restricted to three.

dmmus where 6 motor coaches as in lh/rh engines and axle[dogs engaged ] lights on the cab panel so up to 12 [3x4]coaches but more normal 3x3 or a 9 car
blue star used to be 3 locos as above that the mcbs could trip out
southern used to be 14or may have been 16 power units on 12car lines above that motors had[may have ] to be isolated but no restriction on the control side

 

[hexagon789]

Are there limits on the number of multiple units that can be coupled together? I have a, possibly faulty, recollection that some classes back in the 60s and 70s were restricted to three.

With second generation units, up to 12-cars, six 2-car units, was possible.

 

[hexagon789]

Most of the BR carriage working books I've seen set out a limit of 17 coaches before permission is required to run, with a limit of 13 for trains of air-conditioned Mk2s and 3s, the longest booked formations are generally 12-13 coaches as late as the 1980s.

 

[yorksrob]

London - Dover/Folkestone boat trains could be up to 14 20m long carriages - i.e. a standard 12 carriage EMU, plus Trailer Luggage Van and Motor Luggage Van.

 

[randyrippley]

The later WCML motorail sets used a standard class 90 + mk3 set including DVT (12? 13?) Plus four or five car carriers
must have been the longest passenger sets in use for a long time

but back in the 1970s I was sitting on the sea wall at Dawlish watching Peaks + 16 taking midlanders on holiday

 

[Bletchleyite]

I have the impression that in the UK today that 266m (2 x 25m + 9 x 24m), i.e. an 11-car Pendolino, is the practical limit in most cases (with end-on termini people won't walk too far - 12-car LNR services being full and standing at the back and nearly empty at the front are evidence enough). There are the Sleepers but this is a special case.

 

[hexagon789]

The later WCML motorail sets used a standard class 90 + mk3 set including DVT (12? 13?) Plus four or five car carriers

I thought they were max 9+DVT, with only the Pullman sets being longer which didn't get Motorail's tacked on?

 

[6Gman]

Are there limits on the number of multiple units that can be coupled together? I have a, possibly faulty, recollection that some classes back in the 60s and 70s were restricted to three.

I believe the Blue Square units of the late 1950s (which made up the majority of the Modernisation Plan units) were allowed to operate up to 6 motor cars (there was a set of engine operation lights on a panel which showed up to 6 pairs). So 2car units (motor + trailer) could operate up to 12car formations, but 3car un its (motor+trailer+motor) were limited to 9 cars.

In the 1960s summer Saturday trains along the North Wales coast were sometimes 12car formations.

 

[AndrewE]

I believe the Blue Square units of the late 1950s (which made up the majority of the Modernisation Plan units) were allowed to operate up to 6 motor cars (there was a set of engine operation lights on a panel which showed up to 6 pairs). So 2 car units (motor + trailer) could operate up to 12car formations, but 3car units (motor+trailer+motor) were limited to 9 cars.

In the 1960s summer Saturday trains along the North Wales coast were sometimes 12car formations.

That's exactly as I understand it too (having diagrammed the men for those very trains in the 1970s!) We agree with Big Al.

 

[RPM]

In terms of Chiltern DMUs, 12 is the maximum number of cars that can operate together (in line with most modern DMU classes). However platform lengths dictate that 9 cars is the maximum length of train that can actually be in passenger service on Chiltern, and even then there is only a fairly limited number of stations that accommodate 9 cars. There's one daily 9 car class 168 formation that works from Oxford to Marylebone in the morning peak. I thinks that's the only regular one.

 

[TRAX]

Signal blocks are also a major limiting factor.

 

[class 9]

15x units max 12 vehicles.
14X units max 8 vehicles.

 

[Struner]

I suppose the number of carriages depends on the length of those carriages as well?
Rather short in the UK, I’m afraid.

 

[Ken H]

The Caledonian Sleeper is about as long as it gets nowadays (sixteen coaches, or is it fifteen plus loco, I can't remember - the Sleeper is designed for comfort rather than speed though - no need for breakneck pace to get to London/ Scotland at four in the morning - the idea is to arrive at an appropriate time for waking up, so it doesn't have to go at Pendolino speeds, and is free to drain plenty of juice as there aren't many other services around at that time of day).

But a lot of the problems with train length come down to:

• Platform length (not just the termini but also intermediate stations - I can maybe accept an SDO situation where there's one carriage hanging off the edge of the platform but if you are expecting passengers to walk more than one carriage length to get off at an intermediate station then you may need some hefty dwell times to be on the safe side)
• Fouling junctions (or taking longer to clear junctions)
• Electricity issues (for AC/ DC services, there may be a limit to the power that one train can drain from the juice)
• Locomotive issues (fine on a nine coach DMU, where each carriage has an engine but if the rule of thumb is that longer trains justify loco hauled then there's limits to just how much one loco can haul... you could add a second loco of course but then that lengthens the train even further

As an example, look at the old Southern Region, where they could certainly do with longer trains on a number of services but have maxed out at 12x20m trains (or 10x23m) - to go any longer would mean redesigning several stations/ junctions etc and beefing up power supplies

wont a train with 2 AC locos be restricted in speed because the 2nd panto will hit disturbed wide making current collection difficult and causing sparking.

 

[HSTEd]

15x units max 12 vehicles.
14X units max 8 vehicles.

AIUI it is 12 control systems for Sprinter/Turbostar only formations, which drops to 8 if there is a Pacer is the formation.
Normally that would mean 12-cars, but Class 153s count as two because they have a second set of control gear in the other cab.

 

[Bevan Price]

wont a train with 2 AC locos be restricted in speed because the 2nd panto will hit disturbed wide making current collection difficult and causing sparking.

As far as I know, only freight trains have used 2 AC locos on WCML. Except in case of failure, WCML passenger services were normally worked by single AC locos.

 

[Tomnick]

Signal blocks are also a major limiting factor.

Not really - a long train can happily occupy more than one signal section without drama. A long train standing at a signal and blocking a junction in rear might be a problem, but the signalman should account for it and regulate accord

 

[Indigo Soup]

I have the impression that in the UK today that 266m (2 x 25m + 9 x 24m), i.e. an 11-car Pendolino, is the practical limit in most cases (with end-on termini people won't walk too far - 12-car LNR services being full and standing at the back and nearly empty at the front are evidence enough). There are the Sleepers but this is a special case.

It'll be interesting to see how people cope with 400m HS2 trains.

 

[EM2]

It'll be interesting to see how people cope with 400m HS2 trains.

They happily cope with 400m Eurostars.

 

[AndrewE]

They happily cope with 400m Eurostars.

which have separate signed access stairways and loading areas dedicated for the different parts of the train (at the 2 London termini anyway. Is it the same at Ashford?)

 

[whhistle]

With second generation units, up to 12-cars, six 2-car units, was possible.

Indeed.
There's a picture of a 13 (?) coach Class 156 floating around the internet but can't find it at the moment.

 

[hexagon789]

Indeed.
There's a picture of a 13 (?) coach Class 156 floating around the internet but can't find it at the moment.

12-car I think. All the south of bridge Inverness sets in a lash-up on Culloden Viaduct.

 

[Struner]

http://metcam.co.uk.nstempintl.com/1980s.htm