Skid Control, Rollover Prevention, and Hazard Response
This domain tests how you prevent and respond to loss of traction, rollover risk, and sudden hazards in a combination vehicle. The tractor-trailer's high center of gravity and articulation make recovery different from a car.
Core rules
- Rollover prevention: keep the center of gravity low, distribute cargo evenly, secure loads, and slow down before curves or ramps. Rollover occurs when lateral force exceeds stability, often from too much speed or a sudden steer.
- In a curve, brake before the curve, not during it. Sudden braking or steering while the trailer is leaning can trigger a rollover.
- Drive-wheel skid: release the brake or accelerator, steer in the direction you want the front of the vehicle to go, and avoid overcorrecting.
- Front-wheel skid: release the brake or accelerator and steer straight until traction returns.
- Trailer skid: ease off the brake or accelerator, steer to keep the tractor aligned with the trailer, and avoid abrupt corrections.
- With ABS, brake firmly and steer; do not pump the brakes.
- For hazards, maintain space cushion, identify an escape route, communicate with lights or horn, and slow down smoothly.
Worked example
A tractor-trailer enters a loop ramp above the advisory speed. The trailer leans, the driver brakes hard and steers sharply, and the combination rolls over. The safer response is to slow before the ramp, enter at or below the advisory speed, and make smooth steering inputs.
Traps
Overcorrecting a skid, braking hard while turning, loading heavy cargo high, and waiting until the hazard is close to choose an escape path.