Three-Car Length Rule

Rear-End Collisions and the Three-Car Length Rule

You have probably heard people talk about the “three-car length rule” in driving.  If you haven’t, the supposed rule goes like this: you should always be at least three car lengths behind the vehicle in front of you in order to avoid rear-ending them if they stop short.  I am here to tell you that the three-car length rule is simply not a good or safe metric by which to judge the distance you should travel behind another vehicle.

For example, let us assume you are traveling on the highway on a clear dry day at a rate of speed of 60 mph.  You are three-car lengths behind another vehicle also traveling 60 mph.   The car in front of you suddenly slams on its brakes intending to come to a complete stop due to a hazard in the road.  It takes a person roughly 1 second to see and react to a vehicle stopping ahead of them.   That means at a rate of 60 mph before even applying your brakes you will have traveled 88 feet.  The average car length in the U.S. is approximately 15 feet.  That means you will have traveled almost 6 car lengths before you even have opportunity to apply your brakes.  By the time you come to a complete stop you will have traveled 18 car lengths.

In short, while the three-car length “rule” may be a good rule of thumb for slow, city driving, it simply does not provide a safe, across the board approach to following another vehicle.

If you have been involved in a motor vehicle accident, contact the attorneys at Mobilio Wood today for a free no obligation case evaluation.


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