Double length tube train stopping in random location - thoughts re: capacity?

[Egg Centric]

Thought just entered my head entirely randomly.

Consider a new tube stock which you can walk through (like the NTfL is going to be aiui).

What happens if...

1. You are resignalling the tube line anyway
2. You make it twice the length of any existing platform
3. You give it foolproof selective door opening
4. You do a cunning thing - stop it randomly (with exceptions to e.g. clear junctions) at each stop such that the central 50% is always guaranteed to be at a station (so commuters can position themselves to get off easily ergo no increase in dwell times) but the 25% at either end may or may not be in a platform (so that it loads fairly evenly).

This seems a not bad idea to me but I've been drinking and haven't thought about it for more than a couple of minutes. So there's probably something very wrong with it. What?

Only things I can think of is either some safety rules or perhaps that it couldn't fit in some current infrastructure. These don't feel particularly large issues though.

 

[plugwash]

The problem I see is if the train gets too busy then there is a real risk of getting "trapped" in the end cars and being unable to move to the center section to exit.

 

[Ken H]

Before WW2 the did a 10 car scheme on the northern line. The surface level platforms were extended and the train stopped with different coaches on the platform at the central stations. This from memory so i may have details wrong.
Think the OP is suggesting the revival of an old idea!

 

[edwin_m]

Sometimes it's hard enough to get to the nearest door on a crowded Tube. Trying to get through several coaches doesn't bear thinking about.

 

[zwk500]

The ends that are always off the platform won't be used while the doors that are will be rammed to the gunnels. There's also the capacity impact of occupying twice as much track and the impact on the power network of having to move such a long and heavy beast. There are some tight and twisty sections of the tube network where a very long train may suffer noticeable resistance.
Finally, can you evacuate that volume of passengers from the trains *and stations* in the event of a fire or other emergency?

Its a nice thought, but enough people struggle with stations where the last doors only are locked out, can't imagine what half a train would do.

 

[Snow1964]

Before WW2 the did a 10 car scheme on the northern line. The surface level platforms were extended and the train stopped with different coaches on the platform at the central stations. This from memory so i may have details wrong.
Think the OP is suggesting the revival of an old idea!

It was 9 car (not 10 car) and all the new Northern line stations (basically everywhere north of Hampstead and Golders Green) gained 9 car platforms, guard travelled in car 7, and there were some sort of signs (manually set) on the 2 outer cars about which stations couldn’t alight from. I think the morning Southbound trains then stopped at Tottenham Court Road 2 cars forward (so doors of car 3-9 were in platform).

I think it was a quick fix, late 1930s, abandoned at start of war when only about 10 trains had been formed up. Years later when the 1920s tube stock was replaced passengers were able to use whole train (the older stock had raised frames over the much large motor bogies, so this part was just an equipment compartment. The newer stock had everything under the floor, or under the seats.)

 

[Ken H]

It was 9 car (not 10 car) and all the new Northern line stations (basically everywhere north of Hampstead and Golders Green) gained 9 car platforms, guard travelled in car 7, and there were some sort of signs (manually set) on the 2 outer cars about which stations couldn’t alight from. I think the morning Southbound trains then stopped at Tottenham Court Road 2 cars forward (so doors of car 3-9 were in platform).

I think it was a quick fix, late 1930s, abandoned at start of war when only about 10 trains had been formed up. Years later when the 1920s tube stock was replaced passengers were able to use whole train (the older stock had raised frames over the much large motor bogies, so this part was just an equipment compartment. The newer stock had everything under the floor, or under the seats.)

Thanks for that. Of course it was feltham built 'Standard stock' now you remind me. One of the reasons this wasnt taken forward was 1938 stock had no equipment compartment so passenger carrying capacity was increased without cumbersome solutions like this.
Remember, a 7 car standard stock train would have 4 equipment compartments per train.

 

[Mikey C]

The problem with doing it on the Tube, especially in Central London, is the large number of visitors using the service, who would be completely baffled and miss their stop!

The Circle isn't very frequent or fast, so I assume it doesn't impact timetables, but the S7 trains being a carriage too long for Baker Street must slow boarding down a bit.

 

[TSG]

Putting more people on a train that doesn't stop very often is an effective way of increasing capacity e.g double deck TGVs.

On a metro, capacity is not just about how many people you can get on each train. AIUI dwell times and, related, how quickly you can reoccupy the platform with another train, as well as how quickly you can get people in and out of the stations are big factors. I suspect what you propose is likely to result in increased dwell times at each platform as people struggle to get to the doors. The additional length would combine with the increased dwell time to worsen the headway. This would reduce capacity of the train service. It would probably also result in passengers milling around stations trying to double back to a missed stop, which would reduce the capacity of the stations.