Two options:
The quickdrive rule, as suggested by Captainkman, allows you to change freely.
The second option is a rule which can be added into the session commands. When triggered by something (Example, locomotive running over a piece of track) then the rule activates, changing the controls to what you assigned. I can't remember the name of this rule off the top of my head - I'll check later as I am downloading the UMR route right now...