<P> The two - second rule tells a defensive driver the minimum distance needed to reduce the risk of collision under ideal driving conditions . The allotted two - seconds is a safety buffer, to allow the following driver time to respond . </P> <P> To estimate the time, a driver can wait until the rear end of the vehicle in front passes any distinct and fixed point on the roadway--e.g. a road sign, mailbox, line / crack / patch in the road . After the car ahead passes a given fixed point, the front of one's car should pass the same point no less than two seconds later . If the elapsed time is less than this, one should increase the distance, then repeat the method again until the time is at least two seconds . </P> <P> One can count the duration of time simply by saying "zero...one...two" but for greater accuracy, it is suggested that drivers say "only a fool breaks the two - second rule". At a normal speaking rate, this sentence takes approximately two seconds to say, and serves as a reminder to the driver of the importance of the rule itself . </P> <P> The TailGuardian distance advisory decals recently adopted by Stagecoach Buses in the UK use the two - second rule in their calibration . Advisory Decals for 30, 50 and 70 mph are calibrated to be invisible outside those safe distance, only rendering themselves visible once the car following has entered the safety zone for the speed that they are travelling . </P>

The 3-second rule is a simple way to