That looks pretty cool, but what happens if I start wandering around the train and the car detatches to go to Whothefuckknowswhere?
I originally was going to say “Well, you don’t allow movement throughout the pieces of the train going to different destinations”.
On the other hand, it might be interesting to have two-car trains where the back car stops at every station. Just keep walking to the front car until your stop is next and you get a non-stop ride.
You get on the (single) car at a stop. The car leaves the station. The front car of the train after yours catches up and couples. People move between the cars depending if they want to get off at the next stop or not. The cars decouple, the front car (yours) breezes through, the back car stops. The front car catches up with the back car of the train ahead of it. People transfer between cars as desired. At the next station your car, now the back car, is the one that stops. Repeat from beginning.
I would think there is about as much chance of that happening as there is of filling the air with 21st-century Hindenburgs.
The first non-stop train model was basically a large bus that carries a smaller bus stop along with it, trading out the bus stop at each destination for a new one. You would have to move through the different peices of the train onto and out of the ‘bus stop’ car for that to work, just like you have to get on and off a bus.
As for your proposed two-car plan, anybody going on a long trip would have to constantly move to the front car as it passed intermediate stops. That sounds really annoying, particularly if you have luggage or children.
And both plans have problems if more than one car/‘bus stop’-ful of people want to get on/off the car at a given single destination. Or do you not sell tickets to people if the destination they want is already full? At times you’ll effectively constrain your passenger load to a few times the capacity of the loader/unloader car.
Sure, you could make it out of metal. You just reduce eddy currents the same way transformer and inductor cores do: laminations. Make the tunnel sections out of rolled-up tubes of sheet metal.
Well, not literally Concordes, but their 21st-century supersonic, possibly scramjet, equivalent.
I was thinking in terms of subways or intracity light rail. These usually stop at every station anyway. If you don’t change cars, you’d stop at every other station… so your trip time would still probably be cut down. You might still have to change cars once to make sure you weren’t in the front car when your stop finally came up.
It doesn’t really have to be two cars. It can be the front part of the train and the back part of the train. Work out the normal volume of a given station at a given time of day and only the necessary cars stop. It could vary from station to station.
If the train length is significantly longer than the proportion of cars the stop at any given time, you also don’t have to move to the front as often to avoid stops… you may have to move towards the back to make sure you don’t miss your station, though.
Right, you’d be adjusting the length of train to try to balance the opposing issues of people who want to go far having to move forward, and the people who only want to go a stop or two having to move back - using the same aisle, mind you. 
And yeah you could vary the number of cars dropped and added to adjust for capacities coming and going, but you still have to make darn sure that it’s clear which car is going to end up where.
Sounds like something between a logistics challenge and a logistics nightmare, I don’t know which. In any case I’d predict a not-insignificant number of people being dumped off too early or carried onward too far ('cause lots of people are kind of dumb). Add in the fact that every car pretty much has to be an engine, or at the very least all the engine cars will have passengers running back and forth through it, and I’m not seeing how this setup would be practical.
During the day, everyone comes from the suburbs into the city. So half the train disengages and stops at Grand Central or Wall Street, or wherever; and only a few people want to board the train at those stations. Where do you put those extra, empty cars? Do you just park them all day until the stock brokers go back to the 'burbs? That’s not a very efficient use of your trains, making only two trips per day.
Well, with all this walking you might as well just forgo seating altogether. :dubious:
Certainly all aspects of having passengers moving between cars during transitory coupling would be a significant factor in the design of the cars. I personally imagined having two aisles, one for each direction of foot traffic.
Most subways I’ve ridden on would benefit from making it clearer where the cars are going to stop. Granted that’s as a tourist, with daily use the quirks of the systems would probably have become clear.
You don’t have to keep moving around unless you want the non-stop ride. Basically, all you’d have to do is verify that the car you’re in will stop at the station you want, and move to the other half of the train if it doesn’t. Then you can treat the system the same as any other subway system (e.g. sit down and wait for your stop). It’s faster, though, because the car skips half the stops.
About “engine cars”… I’m under the impression that on many systems each car has electric motors that propel each car. I can’t recall seeing any system that has identifiable “engine cars”. I have seen cars modified to have a conductor’s box… but this looks like a superficial modification with no clear benefit (I assume it’s because of a train worker’s union/lobby keeping laws that say the trains can’t be fully automated).
In the highly optimized variable length system with the number of cars in the train changing through-out the day to accommodate the shape of traffic, it would probably be preferable to have a highly automated set-up.
Mostly-empty cars pulling out of mostly-one-way-passenger-flow stations to go back into circulation would be no different in this system than in regular whole-train-at-every-stop system… so I’m not sure what prompted your question.
Actually, parking unneeded cars would be very efficient use of the trains compared to the alternative of having (mostly) empty cars circulating around the system during off-peak times. Traditional systems don’t seem to have the capability to change system capacity at a car-level resolution.i. a least not throughout the course of the day.
How wide are these cars again? With two aisles, presumably a row of standing people between them (for other people to shove through), and did you still want seating along the side walls?
Admittedly maybe subway cars/tunnels are that wide; I’m in Boise and the closest we get to a subway system is that some of us have basements. Regardless, I’m just pointing out the small problems with the system along with the large.
You didn’t have to run along the train hoping against hope to get to your car before the doors closed and it (or you) dropped off the back of the train, though, I bet. 
How many cars does a subway train usually have? How many cars are we loading/unloading per stop, again? And remember, you have to wait until your exit car is picked up before you can move forward onto it. If it’s going to be added before your entry car is dropped, you could theoretically wait until it was added on, and then race along the train to get there before the train gets to that stop - but in reality you’d see your cars filled with people shuffling forward constantly as cars were picked up, to avoid being dumped off early - until they got to their car, that is, at which point they’d likely stop in the aisle and block the progress of people who need to keep moving forward, knowing people and the likely amount of seating.
I predict a lot of fistfights on this train.
Illusion of saftey. Cows on the (subway) track and all that; you need a human watching out the front so that you know he can slam on the brakes and reduce the speed by seven miles per hour before you plow into whatever obstructions you come across.
I concede that it should be fully automated, of for no other reason that the driver would have to keep moving forward too.. That’s clearly a comedy sketch gone wrong, so I agree that if this system were done it would have to be automated - though you’d probably still want to station a man on each car to keep people moving and break up fights.