I've been using rest stops for years, almost entirely in passenger 
cars, from '73 Beetle and up. 90% of the time I was alone in the car... 
and about 30% I was alone at the rest stop. Most of these have been 
stops in CO, NM, and UT, but with some in CA, AZ, and all along the 
I-81 corridor. Not all of them were on Interstates, but most were. I've 
only done it in the camper 2 or 3 times, and I would never pop the top- 
I ALWAYS lock myself in, with a clear path to the driver's seat and 
keys handy to the ignition.
I've never, ever, had a bit of trouble. Not even solicitation for 
intimate company, even when I was young and reasonably attractive!
Your mileage may vary- I'm a big, heavy honkey, so maybe that has 
something to do with it.

-Simon

�It�s ridiculous claiming that video games influence children. For 
instance, if Pac-man affected kids born in the 80s, we should by now 
have a bunch of teenagers who run around in darkened rooms and eat 
pills while listening to monotonous electronic music.�
-PC World NZ, 2001