I think you've either got to pad the meeting time or setup a seperate
appointment for the travel.

When I set up my boss's meetings, I put a 30-minute appointment in he
calendar called "Travel Time" at each end of the offsite meeting.
change the color to purple indicating "out of office." On the "Trave
Time" appointment, I set the reminder for 5 minutes beforehand so tha
she can close down her computer, etc., before departing. I find tha
this works better than simply padding the meeting time, because i
eliminates ambiguity. Otherwise people aren't sure if the meetin
actually STARTS at 2:30 and you really need to leave at 2:00, or i
the meeting starts at 3:00 and you've already built in the trave
time