Handling Skids, Jackknifes, and Emergency Situations
What this domain tests
This domain tests recognition and correction of skids, jackknifes and emergency situations in a combination vehicle. The exam expects quick, correct actions: release the brake that caused the lock-up, steer deliberately and avoid compounding the skid.
Core rules
- Skids usually start with too much speed, hard braking, abrupt steering or a slippery surface. An empty combination can lock drive wheels easily because there is little weight on them.
- For a rear-wheel or drive-wheel skid, stop braking and turn the steering wheel in the direction of the skid, toward the side the rear is sliding. Do not steer away from the skid.
- For a front-wheel skid, release the brakes, steer straight ahead and let the front wheels roll until traction returns.
- A jackknife is a severe fold between tractor and trailer. If the drive wheels lock, the tractor can swing; if trailer wheels lock, the trailer can swing. Release the brakes and steer to pull the combination straight. Do not add hard acceleration on ice.
- If you must leave the road, slow gradually, avoid hard braking and return to the pavement only when you can steer gently. A sudden return can roll the vehicle.
- Use ABS as designed: firm steady pressure, steer, do not pump. Keep enough following distance so you do not need emergency braking.
Worked example
A loaded tractor-trailer enters a wet curve too fast. The trailer wheels lock under hard braking and the trailer swings to the left. The driver should release the brake pedal, steer left to follow the trailer's direction and straighten the combination, then brake gently once the wheels roll. Holding the brake or steering right would increase the jackknife angle.
Traps
Steering away from a rear skid, pumping ABS brakes, braking hard after running off the shoulder, and using cruise control on slippery roads are common errors. Also do not assume a light load is safer in a skid; it can lock wheels more easily.