This was somewhere on /r/askscience awhile back. I think that consensus was that small animals like cats or rabbits basically have a fleeing response when encountering big, smelly, loud and dangerous things like lions, tigers, hippos or cars. Now, the best tactic to run away from a usual large, running animal is actually bolting in its direction - the big animal can't change its direction that quick and by the time it stops, turns and checks where the little bugger went, the critter will be far, far away.

This tactic worked soundly for millions of years, but appears quite lethal once predators became balls of metal running at tens of kilometers per hour.