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District of Columbia driving lesson · Safe Driving Fundamentals

Following & stopping distance

A 3-minute lesson from the District of Columbia course. Read the rules and examples, follow the handbook page references, and check your understanding before you move on.

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Read time
3 minutes
Course unit
Safe Driving Fundamentals
Checkpoint questions
4
Source pages
24, 25

Most rear-end collisions are caused by following too closely. The space in front of you is your time to react if the car ahead stops suddenly, so leave as much as you possibly can.

Know the rule

Leave as much space as possible between you and the vehicle ahead to allow for a sudden stop.

Handbook p. 24 ↗

The counting method:

  • Watch the car ahead pass a reference point, such as a sign or overpass
  • Count "one thousand one, one thousand two, one thousand three, one thousand four"
  • If you reach the same spot before you finish counting, you are following too closely
Handbook p. 24 ↗
4 seconds

Minimum following gap by the counting method

Handbook p. 24 ↗
4 to 5 seconds

Following distance in bad weather

Handbook p. 24 ↗

Know the rule

Allow more following distance than usual behind vehicles that stop often, such as buses and post office vans.

Handbook p. 24 ↗

Know the rule

Don't cut trucks off. It takes much more time and distance for a truck to stop.

Handbook p. 24 ↗

Your actual stopping distance depends on:

  • Time to see and recognize that there is danger
  • Time from perceiving danger to starting to brake (3-4 seconds)
  • Type and condition of the pavement
  • Percentage of grade of the roadway
  • Kind and condition of tire treads
  • Vehicle design and condition of shock absorbers
  • Type and condition of brakes
  • Direction and speed of the wind
Handbook p. 25 ↗
3-4 seconds

Driver reaction time used for stopping distances (U.S. DOT tests)

Handbook p. 25 ↗

Put it into practice

The car ahead passes an overpass and you count. You pass under it at "one thousand three." You're too close. Ease off until you can count to four, and in rain open it up to four or five seconds.

Check your understanding

Read the question, decide on an answer, then open it to check the explanation. These are Roadwise study questions based on the source handbook.

How long, per the counting method in the handbook, should you be able to count after the vehicle ahead passes a fixed point to confirm a safe following distance?
  1. 1 second
  2. 2 seconds
  3. 10 seconds
  4. At least 4 seconds

Answer: At least 4 seconds

Count 'one thousand one' through 'one thousand four'; if you reach the same spot before finishing, you're following too closely.

Handbook p. 24 ↗
In bad weather, how many seconds of following distance does the handbook recommend?
  1. 4 to 5 seconds
  2. 1 to 2 seconds
  3. 2 to 3 seconds
  4. 8 to 10 seconds

Answer: 4 to 5 seconds

In bad weather, increase your following distance to four or five seconds.

Handbook p. 24 ↗
What type of vehicles should you allow extra following distance behind, according to the handbook?
  1. Sports cars
  2. Vehicles that stop often, like buses
  3. Small economy cars
  4. Motorcycles only

Answer: Vehicles that stop often, like buses

Vehicles that make frequent stops, like buses or postal vans, deserve more following distance than usual.

Handbook p. 24 ↗
Roughly how long does it take a driver to perceive danger and begin braking, per the handbook's stopping distance guide?
  1. Less than 1 second
  2. 1-2 seconds
  3. 3-4 seconds
  4. 6-8 seconds

Answer: 3-4 seconds

The handbook estimates perception-to-braking reaction time at 3-4 seconds.

Handbook p. 25 ↗
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