For a 40-foot vehicle at 35 mph in good conditions, what is the minimum following distance in seconds?

• A. 2 seconds
• B. 3 seconds
• C. 4 seconds
• D. 6 seconds

Answer: (C)

A larger vehicle needs more space to stop safely, because its stopping distance is longer and you have more momentum to overcome. For a 40-foot vehicle traveling at 35 mph in good conditions, the minimum you should maintain is four seconds. That four-second cushion gives enough time for you to perceive a hazard, react, and bring the vehicle to a stop without hitting the vehicle in front.

If you tried to follow more closely, like two or three seconds, you’d have roughly 100 to 150 feet of space at 35 mph—usually not enough for a 40-foot vehicle to stop in time. Six seconds would be extra protection, but the minimum required is four seconds. Remember to increase the distance in rain, snow, or other adverse conditions.