Commercial Driver's License

Answer: C - To calculate the space you should keep in front of you, use the following formula: If you are going under 40 MPH, use 1 second for each 10 feet of your vehicle length. If you going over 40 MPH, you can use the same formula but add 1 second to the total. In this particular case, if you are driving a 40 foot long vehicle, you should be behind the vehicle in front of you by 4 seconds. This rule applies because you are driving slower than 40 miles per hour.