Handling Skids, Sway, and Emergency Situations
Handling Skids, Sway, and Emergency Situations
This domain tests your response when a multi-trailer combination loses grip or begins to oscillate. Expect questions on skid correction, sway control, jackknife prevention, and trailer breakaway.
Skids
- Causes include too much speed, hard braking, hard steering, and poor traction.
- Correct a skid by releasing the brakes so the wheels roll again, then steering in the direction of the skid. Do not overcorrect; a second swing follows a hard correction.
- If a rear trailer skids, ease off the accelerator, hold the steering steady, and let the combination straighten.
Sway
- Sway is side-to-side oscillation, caused by speed, an unbalanced load, crosswinds, a sudden steering input, or bad suspension.
- Correct it by easing off the accelerator and holding the wheel steady so speed drops gradually. Brake gently only if you must.
- Never use the trailer hand valve to fight sway.
Emergencies
- To avoid a jackknife, brake smoothly, keep a long following distance, and steer gently.
- If a trailer breaks away, its emergency line parts and its spring brakes lock. Keep the tractor straight, slow gradually, get off the road, and set out warning devices.
- After a tire blowout, hold the wheel firmly, keep the combination straight, ease off the accelerator, and slow gradually without hard braking.
Worked example
An empty rear trailer begins to sway at highway speed in a crosswind. The driver brakes hard; the sway worsens and the trailer swings into the next lane. Reasoning: hard braking transfers weight and amplifies the oscillation. The correct response is to release the accelerator, keep both hands on the wheel, steer straight ahead, let the combination slow, then pull off and check the load and tires.
Traps
- Steering away from the skid instead of into it.
- Using the hand valve to stop sway.
- Hard braking or sharp countersteering when a trailer starts to swing.