Why are there gangway doors in BR DMUs

[akmatov]

^ British DMUs seem designed for one engine/passenger unit front and one rear with perhaps several purely passenger cars between. So why do they have gangway door in the front of the engine/passenger units? Afaik, they always have the rear unit with the driver's cab facing to the rear to facilitate flipping the lead unit as desired. What purpose does this ugly door serve?

[CrazyGecko]

To allow passengers to move from one unit to another when it's being operated in multiple.

[Rocket Witch]

Some station platforms in the UK are especially short, so passengers need to be able to travel the entire length of the train when (dis)embarking.

So why are certain stations too small? Specifically I can't say, but Britain has both the oldest railway network and a particularly colourful history to go with it. The infrastructure is bound to be more than a bit dated in places.

[Goblin949]

This is an requirement to allow people to leave the unit in an emergency in narrow British tunnels.

[MindTheGapHD]

It's to do with flexibility of the rolling stock. Most DMUs (and EMUs for that matter) come in semi-permanent units of a specified length (for DMUs this tends to be 2 or 3 cars long). When there is a higher number of passengers, like during rush hour, a single unit may not have the capacity to carry enough passengers. The end gangways allow for multiple units to be joined up to create effectively one longer train, enabling it to carry more passengers, who are able to move through the length of the train as they please. Also, in certain situations, a train split partway along the journey, with different parts going to different destinations, and the end gangways allow passengers to ensure they are in the correct part of the train for where they want to go. You'll note that not all DMU/EMUs have end gangways, and so it really depends on where they are being used. The points above about short platforms and emergency access are also reasons, and I'm sure there are others too

[akmatov]

CrazyGecko - I have never seen a DMU or EMU configured with an engine/passenger unit connected with the driver's cab end facing into the rear of a passenger unit, ie they appear to always be connected with the driver's cab end of both engine/passenger units facing out - so there would not be a car in front of the driver's cab end for a passenger to step into. Or as in the OP "Afaik, they always have the rear unit with the driver's cab facing to the rear to facilitate flipping the lead unit as desired."

[akmatov]

Millhiore F. Biscotti - If a passenger at any station were to exit via the Driver's Cab gangway door, they would exit falling to the ground between the rails as the exit it out the front of the train, not to the side where the platform is.

[CrazyGecko]

Our DMU's are mix of units with a cab at one end only and others with a cab at both ends. When used in multiple the door directly to the cab on the left will be closed but the door to the front can still be accessed by passengers. But each country has it's own preference on how their DMU and EMU are designed

[akmatov]

My current theory is that many of these units were designed on the cheap. The Pacer DMUs were basically a bus body mounted on a railway car. Suspect many later DMUs were lightly modified subway units which might have doubled up with the rear unit facing forward for some reason. This might explain the similarity between the later Sprinters and subway units, with the driver's cab the size of a broom closet with a front view through a key hole and a gangway exit useful in a subway tunnel in an emergency.

[CrazyGecko]

In the UK trains would often split or join on some journeys so this way passengers can move between them without having to wait for station stops.

Pacers were built on the cheap and based on a bus otherwise the branch and rural lines they travelled on would've closed as the profits werent high. DMU's like sprinters are more purpose built and ideal for longer runs.

[akmatov]

I have the idea the MUs usually operated either in sets or added passenger cars between the engine/passenger units. Neither living in the UK or living in the UK when some of these trains were running, I have to go with images which may well be giving me a wrong idea that driver's cab were always connected facing out so as to facilitate changing direction of the train set. Certainly have seen lots of images of steamers double heading nose to tail..

New to train sims and quite a learning experience. The post-war period seems to have been quite a mess with BR wanting to close routes and communities dependent on them for contact with the rest of the world. Haven't yet read it, but I'm guessing pulling branch rail service destroyed some of the communites along those lines. So much to learn. The idea for the Pacers was excellent, my only grumble is as a hobbiest trying to get them up the hills of Wales. Like driving an old VW bus in the hills. :)

[Rocket Witch]

Originally posted by akmatov:

Millhiore F. Biscotti - If a passenger at any station were to exit via the Driver's Cab gangway door, they would exit falling to the ground between the rails as the exit it out the front of the train, not to the side where the platform is.

That's not what I meant.

Say you're onboard a 12-car train made up of three 4-car sets. You entered close to the rear end of the train. You're approaching a station platform that is shorter than the length of the train, so the guard says over the PA that anyone getting off at this station must do so from the front half of the train. Because of the gangways bisecting the driver cabs at the ends of each 4-car set, you can travel all the way from the rear car to the front one in order to alight at the short-platformed station.

[cuavas]

Originally posted by CrazyGecko:

To allow passengers to move from one unit to another when it's being operated in multiple.

This is the answer, just expanding on it. DMUs and EMUs are typically formed into semi-permanently coupled sets. Adding or removing cars from a semi-permanently coupled set requires a trip to the workshop, and is time-consuming and labour-intensive, so you want to avoid it if possible. A semi-permanently coupled set will usually have a driving car at each end for bidirectional running and zero or more intermediate non-driving cars. If we call a driving car “D” and a non-driving car “N”, common configurations are D-D, D-N-D, D-N-N-D, D-N-N-N-D, and so on.

Now you can make all your semi-permanently coupled sets one length and just run them individually, but that’s relatively inflexible. To allow running different length trains, the semi-permanently coupled sets usually have fully automatic couplers at each end (often SchaKu type) so they can be quickly joined together or split.

This allows services that diverge, with part of the train going one way and part going the other way. For example in Australia, VLocity services from Melbourne run to Ballarat as a six-car set composed of two semi-permanently coupled 3-car sets (D-N-D-D-N-D), then split into two three-car sets (D-N-D), one going to Ararat and the other going to Maryborough.

It also allows running smaller sets at times of lower demand for efficiency. For example you might want to three-car sets during off-peak periods and leave the other cars stabled.

If you have end gangways on the driving cars, it’s possible for passengers (and crew) to move through the entire length of a train when multiple semi-permanently coupled sets are joined together. There are various convenience and safety motivations for this. It comes at a trade-off of not allowing a full-width cab. If end gangways are required, the cab is usually more cramped, and has poorer visibility.

[JJTimothy]

Originally posted by akmatov:

My current theory is that many of these units were designed on the cheap.

In spite its reputation, largely fostered by political hostility, BR ran one of the more efficient and frugal railway networks. Case in point the APT which is largely presented as a white elephant costing hundreds of millions of pounds and achieving nothing. In fact the whole project cost around £30m and the research revolutionised high speed rail travel all over the world. So yeah- BR did everything as inexpensively as it could but not necessarily on the cheap.

Originally posted by akmatov:

The Pacer DMUs were basically a bus body mounted on a railway car.

Indeed but it still had to meet standards such as resisting a 200 ton crushing force which just plonking a 'bus body on a rail chassis would not achieve.

Originally posted by akmatov:

Suspect many later DMUs were lightly modified subway units which might have doubled up with the rear unit facing forward for some reason.

The Sprinters body shells were based on Mk.3 coaches. The cab end doors, by no means a new feature, are indeed there to allow passengers to move throughout the train when working in multiple.

Originally posted by akmatov:

I have the idea the MUs usually operated either in sets or added passenger cars between the engine/passenger units.

Typically D/EMUs are kept as sets that can be coupled together to make a longer train when required- somethings joining and splitting in service as noted above. I remember going in to Birmingham from Stourbridge to see my dad at work on what would typically be a three car DMU but if we went with him in the morning the train would be three or four units and ten or twelve coaches. (Most of those DMUs were strictly cattle class though with compartments- you couldn't even walk from one end of a coach to the other.)

Originally posted by akmatov:

The post-war period seems to have been quite a mess with BR wanting to close routes and communities dependent on them for contact with the rest of the world.

It might well be argued that Britain's railways have never recovered from the War.

[akmatov]

* 'on the cheap' while a bit negitive, also reflects that in order to maintain the branch lines against some degree of opposition by ppl who didn't rely on them, the costs had to be kept to a bare minimum. A Class 142 with all it's faults was vastly better than no train.
* 'The cab end doors, by no means a new feature, are indeed there to allow passengers to move throughout the train when working in multiple.' Maybe one day I'll see a D/EMU connected with an engine unit connected snout to rear of passenger unit, so far never have, but new to this.
* The railroads in the US were also run into the ground during WW2 and I've read it was one of the reasons for the development of the Interstate Highway system.

[Jack.Grave]

Well british Rail Class 142 is not the only example of Bus on rails, here in Czech Republic we have CD Class 809/810 + 010 coach and its slightly modernized variant CD Class 814 (in permanetly coupled configuration 814+014+914, where 914 is "DVT" or 814+914). Those are even today backbone of secondary lines transport even they are more than 40 years old.
For me as an continetal fellow British DMU/EMUs with ganway door on its nose looks quite odd, also I doubt that someone will travel trough drivers cabin unless its emergency. Jack