Ok, it's a hard problem, but there's gotta be a way. Maybe the coupling mechanism could be something long that extends from the back of the train. The cars can

Ok, it's a hard problem, but there's gotta be a way. Maybe the coupling mechanism could be something long that extends from the back of the train. The cars can connect can over a wide range of distance, kind of like a runway. The connection is made with a friction clutch that can be applied gradually and eased off if something goes wrong. The coupling also has a drive to pull the cars together after they are securely linked. They could always slow down to make the link too.