transportation that is local in nature ( to/from the hotel for example) is considered part of your rest time.

even though we all know that means that 8 hours free from duty equates to maybe 6 hours of sleep time.

the catch all is that every pilot has to determine whether the "rest" is sufficient to go flying. In other words, are you fit for duty or not. If the answer is no, or the story to the NTSB is I was soooo tired and guess I shouldn't have flown....then don't.