The stopping distance of a car traveling at 50 mph under ideal driving conditions is approximately

When you're driving at 50 mph under ideal driving conditions, your perception distance is about 37 feet, your reaction distance is about 55 feet, and your vehicle's braking distance is about 146 feet. Hence your total stopping distance equals 37 + 55 + 146 = 238 feet. This means that if a hazard occurs less than 238 feet ahead, you won't be able to stop in time to avoid it.