Decent little game with no real prep or cost. I would suggest sticking to three "static" vehicles to make it easier for everyone to remember. At times some had a hard time remembering what their car was, so perhaps some kind of marker for them to "wear" would help with that.
Definitely want to do this with a larger group than the 10 I did this with. It was still fun but the groups got small real fast.
Other then that, good game.