I wanted to add for vehicles I always carry the "4 pack" of powerbars. 2 chocolate and 2 peanut butter. I just grab them when I'm at WallyWorld or the like.
I recently had one after I'd worked all day and had no time for lunch and was getting very hungry, I new I was 1hr away with traffic so I figured it was time to jump into the stash <img src="/images/graemlins/smile.gif" alt="" />
(Note about power bars: WHen it's cold they NEED to be warmed up to chew/eat)