You are driving at 35 mph in a 40-foot vehicle. The visibility is good and the road is dry. What is the minimum spacing in front of your vehicle that you should maintain for safety?

How much space should you keep in front of you? One good rule says you need at least 1 second for each 10 feet of vehicle length at speeds below 40 mph. At greater speeds, you must add 1 second for safety. For example, if you are driving a 40-foot vehicle, you should leave 4 seconds between you and the vehicle ahead. [California Commercial Driver Handbook]