Stopping at 55 mph using a 5-second safety cushion

• A. 5's safety cushion, 400ft traveled, 340ft distance to stop
• B. 4's safety cushion, 320ft traveled, 340ft distance to stop
• C. 5's safety cushion, 320ft traveled, 360ft distance to stop
• D. 5's safety cushion, 420ft traveled, 360ft distance to stop

Answer: (A)

The key idea is to split stopping distance into two parts: the distance you cover while you react (the safety cushion) and the distance you travel after you start braking (the braking distance). At 55 mph, you’re moving about 80.7 feet each second. A five-second safety cushion means about 5 × 80.7 ≈ 400 feet of travel before you begin braking. After braking starts, you’d need roughly 340 feet to come to a stop under the given conditions. So the option that lists a five-second cushion with about 400 feet traveled and about 340 feet to stop matches these calculations. The other choices either imply a shorter cushion (like four seconds) or a different braking distance, which don’t align with the five-second cushion concept.