There is another way, but it requires that the start time on the session stays the same.
Schedule Rule (built-in from TRS2004/6 onwards (I cannot confirm whether it does work with TRS2004, but I can confirm it works with 2006 and above)) will allow you to set times for a train to arrive/leave stations etc (make sure you select the track number and command correctly)
You will probably need 3 schedule rule items (one for each train - make sure you select the right train at the top of the rule) then you can add Drive Schedule as the only command (unless you want him to go to a portal or remove after) for each train in Driver Setup.
Shane