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## Four-second rule 

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NOTE:  While this chart recommends the use of the 4 second rule, 13 AAC 02.090 requires at a minimum the 2 second rule. 

## SPEED, IMPACT AND BRAKING DISTANCE 

It is a well-known fact that the faster you drive the greater the impact or striking power of your vehicle. A fact not generally understood is how much greater the striking power of a vehicle is when you double the speed from 20 to 40 miles per hour. It is commonly believed that the striking power of a vehicle would likewise be doubled. This is not true. The impact is 4 times greater at 40 mph than at 20 mph. The braking distance is also 4 times longer. Triple the speed from 20 to 60 mph and the impact and braking distance are 9 times greater. Increase the speed to 80 mph and the impact and braking distance are 16 times greater than at 20 miles per hour. 

Respect the potential destructive power of your vehicle when you increase speed. Speed properly related to traffic, road, and weather conditions, and skillfully controlled by a thoughtful driver need not be hazardous. In the hands of a thoughtless, uninformed driver it is deadly. 

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