Controlling Speed
Controlling Speed tests how you choose and hold a safe speed for traffic, road, load, and weather. The exam covers stopping distance, curves, downgrades, work zones, and the use of brakes and gears. Speed is the variable that most often turns a recoverable situation into a crash.
Core rules
- Obey the basic speed law: never drive faster than conditions allow, regardless of the posted limit.
- Stopping distance grows with speed. Braking distance increases roughly with the square of speed; reaction distance grows linearly.
- Slow before a curve, enter at a safe speed, and accelerate gently after the curve. Braking hard in a curve can cause a skid or rollover.
- On a downgrade, select a low gear before the crest and use snub braking: brake firmly to reduce speed about 5–10 mph, release, and repeat.
- Do not ride the brakes continuously; heat causes brake fade.
- In work zones, slow at the first warning sign and follow flagger instructions.
- Use escape ramps if brakes fail on a downgrade; do not attempt to turn around.
Worked example
A driver traveling 30 mph doubles speed to 60 mph. Reaction distance doubles, but braking distance becomes about four times longer. The total stopping distance is far more than double. That is why a speed that felt safe at 30 mph can be too fast at 60 mph when a light changes or traffic stops. The correct response is to reduce speed before the hazard, not to rely on brakes.
Traps
- Treating the posted speed as a target in rain or traffic.
- Braking continuously down a long grade.
- Entering a curve too fast and braking hard in it.
- Coasting in neutral to control speed.