How many feet does it take to stop car at 25 mph?

Answer 1

A vehicle travels approximately 1.5 ft per second for each mile per hour. 25 x 1.5 = 37.5. Add to that the average human response time to react to stimuli and apply the brake (1.5 sec again) = 56.25 ft before the vehicle begins to stop. Braking on most decent surfaces with good tires slows you 15 feet per second, per second of braking.

37.5 fps to 0 fps = 2.5 sec to stop

(37.5 fps/2) x 2.5 sec = 46.875 ft braking distance + 56.25 reaction distance

= 103.125 ft between recognition of a danger and your vehicle stopping.

Add to that the braking efficiency of the vehicle. You can also account for the drag coefficient of the pavement and grade (.7 to .8) but that is usually a negligible amount unless you are doing serious traffic crash reconstructions.