Is there any way to do this in service mode successfully, without being held up at Red signals due to one of the sets you're coupled to having a different roster or schedule? I've tried and managed to get a 6 or a 9 car formation, but I get held up at signals or get denied a path. I just find 3 car trains quite boring! Cheers in advance!
I believe this confuses the dispatcher because it doesn't recognise your service and therefore blocks you.
In short NO, this is not currently possible due to each 3 car unit having assigned services throughout the timetable. There is talk of 6 car units being added in the future, as they are in scenarios but this may come in a patch later in the year.
