Following distance, night driving and weather

Key points

1. When the vehicle ahead passes a fixed object, count. If you reach the object before one-thousand-three, you are following too closely.

   Source: Handbook p. 83

   “When the vehicle in front of you passes the object, count “one-thousand-one, one-thousand-two, etc.” Your vehicle should not reach the object before the count of one-thousand-three. If this occurs, you are following too closely.”
   Illinois Rules of the Road, Handbook p. 83

2. The three-second rule applies on a good road in good weather. If road or weather conditions are not good, increase your following distance even more.

   Source: Handbook p. 83

   “The three-second rule also applies to your vehicle speed when you are on a good road and during good weather conditions. If the road and/or weather conditions are not good, increase your following distance even more.”
   Illinois Rules of the Road, Handbook p. 83

3. If you are being tailgated, change lanes or slowly pull off and let the vehicle pass.

   Source: Handbook p. 83

   “If you are being tailgated, move to another lane or slowly pull off the road and allow the vehicle to pass.”
   Illinois Rules of the Road, Handbook p. 83

4. Dim bright lights 500 feet before meeting an oncoming vehicle and 300 feet before passing one.

   Source: Handbook p. 87

   “Bright lights must be dimmed 500 feet before meeting an oncoming vehicle or 300 feet before passing a vehicle.”
   Illinois Rules of the Road, Handbook p. 87

5. Illinois law requires headlights whenever you use your windshield wipers.

   Source: Handbook p. 85

   “Illinois law requires you to use your headlights when operating your windshield wipers.”
   Illinois Rules of the Road, Handbook p. 85

6. In fog, turn off cruise control, increase your following distance and slow down.

   Source: Handbook p. 84

   “Turn off the cruise control and increase your following distance. • Slow down.”
   Illinois Rules of the Road, Handbook p. 84

7. If the fog is too dense, pull off and stop. Do not creep along at 5 to 10 mph.

   Source: Handbook p. 84

   “If the fog is too dense, pull off the roadway and stop. Do not drive at 5-10 mph.”
   Illinois Rules of the Road, Handbook p. 84

8. Backing up on an expressway is against the law.

   Source: Handbook p. 86

   “Backing up on an expressway is against the law.”
   Illinois Rules of the Road, Handbook p. 86

9. If you must jump clear of a car touched by fallen power lines, land on both feet and hop or shuffle 50 feet away.

   Source: Handbook p. 88

   “When jumping from the vehicle, land on both feet and hop or shuffle while keeping your arms close to your body for a distance of 50 feet away from the vehicle.”
   Illinois Rules of the Road, Handbook p. 88

Numbers to know

3 questions from the Illinois practice test

1. 1. Which following-distance rule should a driver use in good road and weather conditions?

   1. The three-second rule
   2. A one-car-length rule
   3. A one-second rule at every speed
   4. The distance shown by the vehicle behind
   Show answer

   The three-second rule. Illinois uses the three-second rule to judge a safe gap in good conditions. The driver selects a fixed object, watches the vehicle ahead pass it, and counts until the driver reaches that object. A one-car-length estimate changes with speed and does not provide the manual’s method. Poor weather or roadway conditions require even more space, so three seconds is a starting point rather than a license to follow closely.

2. 2. When must bright lights be dimmed in Illinois?

   1. 500 feet before meeting an oncoming vehicle and 300 feet before passing a vehicle
   2. 1,000 feet in both cases
   3. Only when the other driver flashes
   4. 100 feet in both cases
   Show answer

   500 feet before meeting an oncoming vehicle and 300 feet before passing a vehicle. Bright lights must be dimmed 500 feet before meeting an oncoming vehicle and 300 feet before passing a vehicle. Night driving is difficult because things may appear differently than in daylight, and glare from lights may interfere with vision. Never overdrive your headlights, keep them clean and aimed properly, dim the dashboard lights, and use the edge lines and center lines of the roadway as guides.

3. 3. When does Illinois law require a driver to use headlights because of weather?

   1. When operating the windshield wipers
   2. Only during heavy snow
   3. Only when visibility is reduced by fog
   4. Whenever the temperature is below 50 degrees
   Show answer

   When operating the windshield wipers. Illinois requires headlights when the driver is operating the windshield wipers. The rule is not limited to heavy snow or fog, and it does not depend on a particular temperature. The wipers themselves are the trigger, so the requirement applies in daylight as well as at night. Separately, the manual says lights should be used from sunset to sunrise. When the wipers are on for weather, turn on the headlights as well, and remember that the manual also calls for turning off cruise control and increasing following distance in rain.

Source: the Illinois Rules of the Road, Chapter 11: Safe Driving Tips. 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.