[ant6n]

The solution with fade out / fade in is pretty clever. Short layovers will cross-fade automatically, but you don’t need complicated internal information about which train continues from one run to the next.

Stopping would be neat, but may also be visually messy.

[rob74]

It doesn't have to be complicated though, and it also doesn't need additional information. The trains could simply be "parked" at terminus stations, and when a train is scheduled to depart in the other direction, check if a train is available at the station - if yes, use it, if no, create a new one.