Yes, with a DMU you will need to change the direction of the train at the relevant terminal before the return journey, with a steam, diesel and electric loco you will need to run the loco round the train before the return journey. You will also need to provide the path at the terminals for locos to run round a train if required and to change track for any return journey. On a single track system you will need a passing place somewhere towards the middle of the route. If it is necessary to sync the trains you could use either triggers or the clock i.e. departure times. Peter
Just read 'pware' comments, I am assuming TM means Terminal.