Reaction distance is the measurement of how far a vehicle travels between the time a driver realizes the brakes must be applied and when the driver actually starts pushing on the brakes. If the driver is capable and paying attention, the reaction distance lasts about three-quarters of a second.
Therefore, when traveling about 40 miles per hour, the reaction time is over 13 yards. As speed increases, the reaction time increases. It also increases when drivers are distracted or tired. Reaction time is reduced when drivers keep a sharp eye on the road and anticipate problems such as erratic drivers, road hazards and increasing traffic.