I had a car and to get to Hollywood Studios which is the closest park from the apartments, I left an hour early. If I was driving to MK I'd probably leave at least 2-1.5 hours earlier due to parking and the fact that you take the bus at West Clock to get to your location.
If you're taking the bus, people generally take the 1 bus earlier than they need to to get to work on time. I believe that you don't get points if you made an effort to take an earlier bus and it does happen to break down on the way and you're late to work.