You should know your surroundings at all times when driving. This is what prevents accidents, not knowing what you are going to do at any given moment, but what the idiot next to you on his cell while eating breakfast and shaving is going to be doing at an given moment. If I see that idiot behind me and he isn't stopping, I can potentially avoid the accident by moving over a lane and letting him rear end another car. I've actually had this work in my favor. I was watching the cars around me during a traffic jam and the dump truck 4 cars behind me either had a brake malfunction or just didn't decide to hit them. I moved over two lanes to the right and the dump truck took out the 3 cars behind me and the 2 that were in front of me. I know this is a rare incident, but it worked for me on that day.