I'm a bit surprised to see that nobody has mentioned that this is a very common configuration in the real world, cars linked this way ("coupled, from now until eternity") are called married pairs, or twin units:
http://en.wikipedia.org/wiki/Married_pair
They're falling out of favor on New York's MTA system, but Chicago's newest 5000-series cars are still configured in married pairs.
Hypothetically, with married pairs you never need to turn cars around, each unit is independently functional, and the number of many expensive components is reduced by half. Quite elegant, if you ask me.
Romantically(?) divorce among married pairs is rare, and in the case of Chicago, fan-sites document the handful of mis-matched cars.
On at least one part of the MTA system, the Long Island Rail Road, all the cars are in permanently coupled pairs and have toilets in the odd-numbered cars only. And indeed, they're never turned around: the odd numbered car is always at the west end of the pair.
They're falling out of favor on New York's MTA system, but Chicago's newest 5000-series cars are still configured in married pairs.
Hypothetically, with married pairs you never need to turn cars around, each unit is independently functional, and the number of many expensive components is reduced by half. Quite elegant, if you ask me.
Romantically(?) divorce among married pairs is rare, and in the case of Chicago, fan-sites document the handful of mis-matched cars.