lets put this into perspective for you: The average car is about 10-15ft in length. So you are driving behind someone on a dark road with about a car length in front of you? Why? And to answer your question, when I drive I try not have any less than 2 car lengths in front of me. Yes there have been times when I have been that close to the vehicle in front of me, but that's as I'm preparing to pass someone. at 30or so mph, 1 car length is about half a second to react. I don't think you can react that quick even if you're paying 100% attention to the car infront of you. But sorry about your accident, hopefully the truck owners insurance will pay for it.