Dude, you obviously haven't studied crash safety.
Let's look look at a famous crash test from the 1970's: http://www.youtube.com/watch?v=lgOxWPGsJNY&feature=endscreen&NR=1
I don't mean to single out the Pinto. It was, in fact , typical of many 1970's cars which had fuel tanks mounted behind the rear axle. Cars today are much safer.