You are driving a 40-foot vehicle at 35 mph. The road is dry, and visibility is good. What is the least amount of space you should keep in front of your vehicle to be safe?
How much space should you keep in front of you? One good rule says you need at least one 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.