You are driving a 40-foot vehicle at 50 mph. Driving conditions are ideal (dry pavement, good visibility). What is the least amount of space that you should keep in front of your vehicle to be safe?
The formula for following distance is one second per ten feet of vehicle, plus an extra second if you are traveling over 40 mph. Therefore, for a 40-foot vehicle traveling at 50 mph, you should leave a following distance of 5 seconds.