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The delay before responding
Reaction time is the time between detecting a stimulus and beginning a response. Human reaction times are typically about 0.2 s to 0.9 s, depending on the person and situation. Tiredness, alcohol, certain drugs and distractions can increase a driver’s reaction time. The car continues moving during this delay. At a fixed speed, a longer reaction time means a greater thinking distance: thinking distance = speed × reaction time. For example, 20 m/s × 0.25 s = 5 m.
