Following Distance and Stopping

Key points

1. Stopping distance equals reaction distance plus braking distance, and it takes longer at higher speed.

   Source: Handbook p. 40

   “REACTION DISTANCE + BRAKING DISTANCE = STOPPING DISTANCE”
   Iowa Driver's Manual, Handbook p. 40

2. Use the 3 to 4 second rule to keep a safe following distance in normal traffic and good weather.

   Source: Handbook p. 41

   “using the 3- to 4-second rule will help you establish and maintain a safe following distance”
   Iowa Driver's Manual, Handbook p. 41

3. Beginning drivers should keep at least three seconds under normal conditions.

   Source: Handbook p. 41

   “An inexperienced or beginning driver should maintain at least a three-second following distance under normal driving conditions.”
   Iowa Driver's Manual, Handbook p. 41

4. At 40 mph use 4 to 5 seconds, and 6 or more on slippery roads or when your view is blocked.

   Source: Handbook p. 41

   “At speeds of 40 mph, a four- to five-second following distance is recommended. When road conditions are slippery or the vehicle in front of you blocks your view, a following distance of six or more seconds is recommended.”
   Iowa Driver's Manual, Handbook p. 41

5. Count from when the car ahead passes a landmark; your bumper should not pass it before you count to three.

   Source: Handbook p. 41

   “your front bumper should not pass the landmark before you’ve counted to three.”
   Iowa Driver's Manual, Handbook p. 41

6. To warn drivers behind you of an unexpected stop, tap your brake pedal 3 or 4 times quickly.

   Source: Handbook p. 41

   “tap your brake pedal three or four times quickly. This will let those behind you know you are about to slow down.”
   Iowa Driver's Manual, Handbook p. 41

7. With ABS, press the brake as hard as you can and keep pressing.

   Source: Handbook p. 41

   “Press on the brake pedal as hard as you can and keep pressing.”
   Iowa Driver's Manual, Handbook p. 41

8. You must stop when a visually impaired person with a cane or guide dog is walking in front of or near you.

   Source: Handbook p. 41

   “When a visually impaired person with a cane (often white or red-tipped) or guide dog is walking in front of you”
   Iowa Driver's Manual, Handbook p. 41

Numbers to know

3 questions from the Iowa practice test

1. 1. For a beginning driver in normal conditions, what following gap does the Iowa manual recommend at minimum?

   1. One second, regardless of speed
   2. At least three seconds
   3. Exactly two seconds for every driver
   4. A fixed distance of one car length
   Show answer

   At least three seconds. The three-second minimum applies to an inexperienced or beginning driver under normal driving conditions. It is a time gap, so the physical distance grows as speed increases. An experienced driver may sometimes use two seconds in normal conditions, but that does not replace the beginning-driver recommendation. Slippery roads or blocked visibility call for six or more seconds, making a fixed car-length rule unreliable. Pick a roadside object, count the seconds after the vehicle ahead passes it, and increase the gap whenever weather, speed, or sight distance worsens.

2. 2. Which following-distance rule is the safest and easiest way to judge space behind another vehicle?

   1. Keep one car length for every five mph
   2. Use the Three-Four Second Rule
   3. Stay exactly two seconds behind in all conditions
   4. Follow close enough to read the vehicle's plate
   Show answer

   Use the Three-Four Second Rule. The Iowa manual identifies the Three-Four Second Rule as the safest and easiest way to judge a following gap. It helps preserve enough room to stop if the vehicle ahead slows suddenly. A fixed car-length formula ignores speed, and exactly two seconds is not suitable for every driver or condition. Reading a plate is a visual task, not a safety measure. Choose a stationary landmark, start counting when the lead vehicle passes it, and adjust farther back when weather or visibility reduces the margin.

3. 3. What happens to stopping distance as vehicle speed increases?

   1. It disappears when the brakes are applied
   2. It becomes shorter on every road surface
   3. It stays exactly the same
   4. It takes longer to stop
   Show answer

   It takes longer to stop. Higher speed increases the distance needed to bring a vehicle to a stop. The shorter-distance choice ignores the extra travel that occurs before and during braking, while the unchanged option treats speed as irrelevant. Stopping distance cannot disappear when the brakes are used; braking is the process that reduces motion over distance. Scan farther ahead as speed rises, leave a larger cushion, and begin slowing early rather than waiting for a hazard to be close. A useful cue is to connect more speed with more space required, even when the road and vehicle are in good condition.

Source: the Iowa Driver's Manual, Chapter 4: Braking and Stopping. 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.