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This would not work as well for shorter journeys (but if you're on a short hop, you'd take the 'stops at each station' train instead). BUT ... it possibly could for longer trips, and on overground trains as well.
Each station has a siding. You board the (single) carriage that is sitting there.
Shortly before the arrival of the non-stop train, the carriage leaves the siding and speeds up as it pulls out onto the mainline. It *almost* attains the speed of the non-stop main train, which catches it up and attaches onto the back. The interconnecting doors then open.
Passengers can then walk quickly through the train, stopping when they get to the carriage indicated as the one for their desired destination (the next upcoming station is the car at the back of the train, the station after that is the penultimate car, etc).
As the non-stop train nears the next station, the last car is dropped off the back, and declerates its way down into the station siding so people can get off.
The car then awaits the new crowd getting on prior to the next non-stop passing by (e.g. every 10 minutes)
With regenerative braking a fair proportion [OK - potentially not much, if earlier comments are to be believed!] of the energy required to accelerate the carriage could be recovered and re-used. In any case:
- the forces required would be relatively small because only one car needs to accelerate/decelerate each time.
- the non-stop train portion itself would be extremely energy efficient (esp if maglev) as it can cruise at constant speed forever
Just need to be careful (if you're a ticket collector, sandwich trolley operator, or have had to use the bathroom in the next carriage) that you don't get separated prematurely by mistake!
Rotating platforms version ... [kindachewy, Jul 07 2009]
Up and over version ... [kindachewy, Jul 07 2009]
Oops ... there appear to be more of these already.
Moving sidewalk/platform version ... [kindachewy, Jul 07 2009]
||Why not attach the new carriage to the front? Admittedly, only usable in driverless or drive by wire systems, but that way there would be no need for a separate tunnel/track to accelerate the departing carriage. The carriage can accelerate to the required speed as the main train approaches, and drop the rear carriage as it passes.
||In computing terms, this is a LIFO stack (last in, first out), while yours is a FIFO stack (first in, first out). In fact, I'm left wondering how your system, as proposed, allows for both arriving and departing carriages at the same station. Completely separate platforms and tracks/tunnels for each?
||Which gives me an idea...
I get your point that there is no need for the 'sidings' I mentioned (the carriages are already on the track, so speed up along it and are caught up, or drop off and slow down). This would make for a conceptually simpler system.
||However, practically I would still include them:
a) to avoid highspeed maglev going past the platform with lots of passengers standing close to the edge
||b) to allow places for carriages to be taken out of the way if required.
||Otherwise, I think we are both saying the same thing. In my idea, each carriage leaves its particular station as if up a pit lane on a race track. It joins the main track ahead of the main train, but at almost the same speed.
(It is now the 'last in' car... but has attached to the front, as you also suggested, which puts it in 'first position')
||Meanwhile, the 'first in' carriage (which has made its way gradually to the back of the train) was dropped off and declerated down to arrive in the same station just after the new carriage left.