At 35 mph, how many feet are required to come to a complete stop?

• A. 210
• B. 180
• C. 260
• D. 320

Answer: (A)

Stopping distance is the sum of two parts: the distance you travel while you perceive a hazard and decide to brake (thinking or perception-reaction distance), and the distance you travel while braking to a stop (braking distance). As speed increases, both parts get larger, and braking distance grows roughly with the square of speed. At 35 mph, a typical perception-reaction time of about one second puts you around 50 feet from the hazard before braking begins. The braking distance from 35 mph on dry pavement is commonly about 160 feet, so the total is near 210 feet. That’s why 210 feet is a standard stopping distance at this speed. In worse conditions, like wet or icy roads, the braking distance increases, making the total stopping distance longer; under unusually favorable conditions, it could be a bit shorter but still on the order of a couple hundred feet.