Following Distance and Stopping

Key points

1. Leave at least 1 car length for every 10 mph of speed.

   Source: Handbook p. 32

   “allow at least one car length between you for every ten miles per hour of speed.”
   Mississippi Driver's Manual, Handbook p. 32

2. At 40 mph leave at least 4 car lengths.

   Source: Handbook p. 32

   “@ 40 MPH leave at least FOUR (4) car lengths”
   Mississippi Driver's Manual, Handbook p. 32

3. Leave even more room behind a large truck or bus.

   Source: Handbook p. 32

   “When you are following a large truck or bus, allow yourself even more room.”
   Mississippi Driver's Manual, Handbook p. 32

4. At 20 mph it takes 68 feet to stop.

   Source: Handbook p. 33

   “@ 20 MPH - 68 feet to stop”
   Mississippi Driver's Manual, Handbook p. 33

5. At 50 mph, total stopping distance is 245 feet.

   Source: Handbook p. 33

   “@ 50 MPH - 245 feet to stop”
   Mississippi Driver's Manual, Handbook p. 33

6. At 70 mph, total stopping distance is 415 feet.

   Source: Handbook p. 33

   “@ 70 MPH - 415 feet to stop”
   Mississippi Driver's Manual, Handbook p. 33

7. Bad weather, slick roads, fatigue or alcohol make stopping distances drastically different.

   Source: Handbook p. 33

   “If the weather is bad, the road is slick, or if you are tired or intoxicated, then the distances will be drastically different”
   Mississippi Driver's Manual, Handbook p. 33

8. On the interstate, stay at least 7 car lengths back at 70 mph.

   Source: Handbook p. 57

   “If you are driving at seventy (70) mph, stay at least seven car lengths from the vehicle ahead.”
   Mississippi Driver's Manual, Handbook p. 57

Numbers to know

3 questions from the Mississippi practice test

1. 1. What following-distance guideline does the Mississippi manual give for a vehicle traveling 40 miles per hour?

   1. At least two car lengths
   2. At least three car lengths
   3. At least six car lengths
   4. At least four car lengths
   Show answer

   At least four car lengths. The following guideline assigns at least one car length for every ten miles per hour. At forty miles per hour, that produces at least four car lengths. Two or three lengths leave less room than the stated relationship, while six is not the figure shown for that speed. The purpose is to create time and space when the vehicle ahead changes speed suddenly and to improve the view around it. Increase the gap further behind a large truck or bus, where visibility is reduced.

2. 2. What assumption should be made about the braking distances shown in the manual's chart?

   1. They assume worn tires and a loaded vehicle
   2. They apply unchanged on wet or icy roads
   3. They assume good tires, good brakes, and dry pavement
   4. They measure only the distance after braking begins
   Show answer

   They assume good tires, good brakes, and dry pavement. The chart is a baseline for ideal conditions: good tires, good brakes, and dry pavement. Wet or slick roads, tiredness, intoxication, and other changes can make the actual stopping distance drastically different. The chart also includes thinking and reaction distance, so it is not limited to the period after the brake pedal is pressed. Use the figures as a best-case reference, then leave extra room whenever the road, vehicle, or driver is less than ideal.

3. 3. If you are stopped behind a large truck on an uphill grade, why should you leave additional space?

   1. Its stopping distance increases while it is stationary
   2. It must swing sideways before driving uphill
   3. It needs space behind it to complete a wide forward turn
   4. It may drift backward slightly when starting
   Show answer

   It may drift backward slightly when starting. A large vehicle stopped on an upgrade may drift slightly backward as it starts moving. Leave extra room behind it for that possibility. A wide forward turn is a different maneuver, and stopping distance is not the reason for this precaution while both vehicles are stationary. The manual also advises keeping left within your lane so the truck driver can see you stopped behind. Account for the slope when deciding where to stop.

Source: the Mississippi Driver's Manual, Rules of the Road: Following and Braking. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.