In nearly all cases, rear-end collisions are the fault of the driver of the vehicle in the back. The legal term "duty of care" applies when determining negligence by motor vehicle drivers, who are expected to exercise the duty of car when on the road. Examples of this are driving at a reasonable speed, adjusting speed for adverse road conditions, using the proper turn signals, and following at a safe distance. The general rule of thumb is to allow at least one car's length per 10 mph travelling speed between you and the next car in front of you. So, if you are driving at 50 mph, you will want 5 car lengths between you. This will allow you more reaction time in case the car in front of you stops suddenly, as is the case in our example.