Antilock Braking Systems and Braking
Air brakes and antilock braking systems appear on most North Carolina school buses, and the exam tests both theory and technique. ABS keeps wheels from locking so you can steer while braking hard; it does not always shorten stopping distance.
ABS rules
- Press the brake pedal firmly and hold it. Do not pump the pedal; pumping can turn ABS off.
- You may feel pulsing and hear noise; that is normal. Keep steering.
- The yellow ABS light should come on at startup and go out. If it stays on, ABS is disabled but normal brakes remain. Report it and drive cautiously, especially on slippery roads.
- Check the trailer ABS light if you pull a trailer.
Braking technique
- Use controlled braking: firm, steady pressure without locking the wheels.
- On non-ABS vehicles, use stab braking or threshold braking.
- Downshift before a long downgrade; do not ride the brakes and cause fade.
- Keep at least a four-second following distance for a loaded bus.
Worked example
A car stops suddenly on a wet road. With ABS, you press hard and hold, keep both hands on the wheel, and steer around the car if there is room. You do not pump or release because the pedal pulses.
Traps
- Pumping an ABS pedal.
- Releasing the brake when you feel pulsing.
- Ignoring a steady ABS light.
- Believing ABS guarantees a shorter stop on ice or gravel.