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Illinois driving lesson · Safe Driving Tips

Defensive driving, following distance and speed

A 3-minute lesson from the Illinois 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 Tips
Checkpoint questions
6
Source pages
86, 87

Defensive driving means expecting mistakes from others and leaving yourself time and space to react. Following too closely causes most rear-end crashes. The three-second rule is Illinois' tool for measuring a safe gap.

Know the rule

Always be prepared to react to other drivers, and don't assume you know what they will do. If you can't avoid a crash, stay calm and choose the least dangerous option.

Handbook p. 86 ↗

Know the rule

Following too closely (tailgating) is the cause of most rear-end crashes.

Handbook p. 86 ↗

Using the three-second rule:

  • Pick a fixed object ahead, such as a sign, tree or overpass
  • When the vehicle ahead passes it, count "one-thousand-one, one-thousand-two..."
  • If you reach the object before "one-thousand-three," you're following too closely
Handbook p. 86 ↗

Know the rule

Three seconds is for a good road in good weather. If road or weather conditions are poor, increase your following distance even more.

Handbook p. 86 ↗

Three-second rule distances

Three-second rule distances
SpeedFeet traveled per secondThree-second distance
25 mph37 feet111 feet back
35 mph52 feet156 feet back
45 mph66 feet198 feet back
55 mph81 feet243 feet back
65 mph96 feet288 feet back
70 mph103 feet309 feet back
Handbook p. 86 ↗

Know the rule

If you're being tailgated, move to another lane or slowly pull off the road and let the vehicle pass.

Handbook p. 86 ↗

Know the rule

Driving too fast or too slowly can be dangerous. Adjust your speed to conditions and match the flow of traffic, without going over the posted maximum.

Handbook p. 87 ↗
4x

Doubling your speed quadruples your stopping distance

Handbook p. 87 ↗

How quickly you can stop depends on:

  • How fast you react, physically and mentally
  • The type and condition of the road
  • Tires: large, wide tires with good tread stop faster than small, narrow, worn ones
  • Brakes: newer brakes stop more quickly than older, worn brakes
  • Wind: a strong tailwind can make it very difficult to stop
  • Vehicle type: design, weight distribution, suspension and shock absorbers
Handbook p. 87 ↗

Know the rule

Drowsy driving impairs you even if you don't fall asleep. You may not react in time to brake or steer. Be well rested, stop often on long trips, and keep your eyes active by reading signs and shifting focus.

Handbook p. 87 ↗

Put it into practice

The car ahead passes an overpass and you count. You reach the overpass at "one-thousand-two." You're too close. Ease off and let the gap grow to at least three seconds, more if the road is wet.

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.

What technique helps you judge a safe following distance?
  1. The five-car-length rule
  2. The three-second rule
  3. The two-second minimum only above 55 mph
  4. Matching your speed to the car ahead exactly

Answer: The three-second rule

The three-second rule is the standard method for judging following distance.

Handbook p. 86 ↗
You count only 'one-thousand-two' before reaching the fixed object the car ahead passed. What does this mean?
  1. You are following too closely
  2. This only matters in bad weather
  3. You are too far back
  4. You are following at a safe distance

Answer: You are following too closely

Reaching the object before a count of three means you're too close.

Handbook p. 86 ↗
Doubling your speed doubles your vehicle's stopping distance.
  1. True
  2. False

Answer: False

False. The handbook states that doubling your speed quadruples your vehicle's stopping distance.

Handbook p. 87 ↗
What is the main cause of most rear-end crashes?
  1. Sudden lane changes
  2. Following too closely (tailgating)
  3. Poor headlight aim
  4. Worn tires

Answer: Following too closely (tailgating)

Tailgating is identified as the cause of most rear-end crashes.

Handbook p. 86 ↗
If another driver is tailgating you, what should you do?
  1. Change lanes or slowly pull off to let them pass
  2. Brake suddenly to warn them off
  3. Flash your brake lights repeatedly
  4. Speed up to increase the gap

Answer: Change lanes or slowly pull off to let them pass

Let a tailgater pass by changing lanes or pulling off slowly.

Handbook p. 86 ↗
According to the handbook, which tires will stop a vehicle faster?
  1. Large, wide tires with good tread
  2. Small, narrow tires with good tread
  3. Large, wide tires with little tread
  4. Narrow tires inflated above normal

Answer: Large, wide tires with good tread

Large, wide tires with good tread stop a vehicle faster than small, narrow tires with little tread.

Handbook p. 87 ↗
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