As you are driving along, some part of your mind is probably constantly estimating how much space you would need to brake if the car in front of you suddenly stopped. All too often, however, drivers don’t realize the difference between stopping time and stopping distance. Let’s figure it out. First, let’s assume the road is a uniform surface.Let’s also assume the stopping car is skidding to a halt, so its speed decreases uniformly. Now suppose–just as a guess–a car going thirty takes four seconds to skid to a halt. How long will it take at sixty? Did you say eight seconds? Correct. As you would expect, twice the speed equals twice the stopping time.