Stopping distance, following distance and signaling

Key points

1. Average perception time for an alert driver is three quarters of a second to 1 second.

   Source: Handbook p. 8-5

   “The average perception time for an alert driver is ¾ second to 1 second.”
   South Carolina Driver's Manual, Handbook p. 8-5

2. Average reaction time, moving your foot to the brake, is also three quarters of a second to 1 second.

   Source: Handbook p. 8-5

   “The average driver has a reaction time of ¾ second to 1 second.”
   South Carolina Driver's Manual, Handbook p. 8-5

3. At 50 mph on dry pavement with good brakes, braking takes about 158 feet.

   Source: Handbook p. 8-5

   “At 50 mph on dry pavement with good brakes, it can take about 158 feet.”
   South Carolina Driver's Manual, Handbook p. 8-5

4. Always try to keep a minimum following distance of 4 seconds.

   Source: Handbook p. 8-6

   “keep a minimum following distance of 4 seconds between your vehicle and the vehicle in front.”
   South Carolina Driver's Manual, Handbook p. 8-6

5. Increase your following distance on slippery roads.

   Source: Handbook p. 8-6

   “Increase your following distance: On slippery roads”
   South Carolina Driver's Manual, Handbook p. 8-6

6. Avoid driving next to other vehicles for long periods. You may be in their blind spot.

   Source: Handbook p. 8-7

   “Avoid driving next to other vehicles for long periods of time. You may be in their blind spot”
   South Carolina Driver's Manual, Handbook p. 8-7

7. State law requires a turn signal 100 feet or more before changing lanes, turning or merging.

   Source: Handbook p. 8-9

   “It is state law that you must use a turn signal 100 feet or more before changing lanes, turning left or right, or when merging into traffic.”
   South Carolina Driver's Manual, Handbook p. 8-9

8. Use low beams on rainy, snowy or foggy days so others can see you, and slow down.

   Source: Handbook p. 8-8

   “On rainy, snowy, or foggy days; use your low-beam lights and slow down”
   South Carolina Driver's Manual, Handbook p. 8-8

Numbers to know

3 questions from the South Carolina practice test

1. 1. What minimum following distance should a driver try to maintain behind the vehicle ahead?

   1. One second
   2. Four seconds
   3. Two car lengths at every speed
   4. Ten seconds in all conditions
   Show answer

   Four seconds. The manual recommends keeping a minimum following distance of four seconds. Use a fixed object such as a sign or pole, watch the vehicle ahead pass it, and count until your vehicle reaches the same point. If you arrive before saying the fourth count, reduce speed and repeat the check. One second is too little for normal reaction and braking, while a fixed number of car lengths changes meaning with speed. Bad weather, darkness, and slippery roads call for even more space, so four seconds is a floor rather than a ceiling.

2. 2. What is the average perception time for an alert driver, according to the South Carolina manual?

   1. One tenth of a second
   2. 5 seconds
   3. Three quarters of a second to 1 second
   4. 10 seconds
   Show answer

   Three quarters of a second to 1 second. Perception time is the time and distance it takes to recognize you must stop, and the average for an alert driver is three quarters of a second to 1 second. Reaction time, moving your foot from the gas to the brake, takes about the same. Braking distance is added on top; at 50 mph on dry pavement with good brakes it can take about 158 feet.

3. 3. What braking distance does the South Carolina manual give at 50 mph on dry pavement with good brakes?

   1. About 30 feet
   2. About 158 feet
   3. About 400 feet
   4. About 1,000 feet
   Show answer

   About 158 feet. At 50 mph on dry pavement with good brakes, braking distance alone can take about 158 feet, and that comes after perception and reaction time of roughly three quarters of a second to 1 second each. Total stopping distance is therefore well over 200 feet, which is why following distance and speed management matter so much, and why wet pavement adds even more distance.

Source: the South Carolina Driver's Manual, Section 8: 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.