Safe and correct following distances can be difficult to establish. For this reason the two second rule is used to create a safe following distance at any speed. This rule applies to dry weather conditions and should be doubled to four seconds in the wet.
How it works: Suppose you are driving on a straight road at 30mph, to estimate your minimum safe following distance allow the car in front to pass a fixed object such as a road sign or lamp post. As the rear of the car in front lines up with your reference marker, count two seconds by saying to yourself ‘Only a fool breaks the two second rule’, which takes two seconds to say. If your vehicle passes the same marker before you have finished counting, you will need to increase your following distance and try again.
The two second rule isn’t just for the car in front. If a car is driving too close behind you, you must take their thinking distance into account by leaving a sufficient and safe distance between yourself and the car in front. So if the car in front brakes sharply, you will be able to slow down in good time and also allow plenty of time for the car behind to slow down. Using this rule helps to significantly reduce accidents and reduce collision damage if one occurs.