I'm sure you've heard the cliche, that just cuz your paranoid doesn't mean they aren't out to get you! Carrying pepper spray probably wouldn't be a bad idea, make sure you know how to use it tho, maybe get two and discharge one to make sure you know how it works, how far it sprays, etc. And don't spray it against the wind of course. I think tasers are legal to carry in some areas for self defense also.

Keeping a cell phone handy to call the cops with is a good idea also, if somebody stops a car and gets out, just putting a cell phone to your ear and telling the potential assailants you are telling 911 their car's license plate number might make a diff.

Odds are against this sort thing happening tho, more likely to get injured by somebody driving recklessly out of ignorance then willful malevolence. But its best to be prepared.