Skid Control, Jackknifing, and Emergency Handling
This domain tests skid control, jackknifing, and emergency handling. The exam wants the immediate corrective action, not a long recovery plan: release the brakes, restore rolling, and steer deliberately.
Core rules
- Skids usually begin with overbraking, oversteering, or too much speed for conditions. ABS helps prevent wheel lock; keep firm, steady pressure and do not pump the brake.
- If wheels lock, release the brakes to regain rolling traction, then steer in the direction the vehicle needs to go. Avoid overcorrecting.
- A drive-wheel skid can lead to a jackknife: locked tractor drive wheels lose side grip, and the trailer pushes the tractor out of line. Release the brakes and steer to straighten.
- For a trailer skid, release the brakes and steer to keep the tractor aligned with the trailer; do not steer sharply against the swing.
- In a blowout, hold the steering wheel firmly, avoid hard braking, slow gradually, and pull off. If brakes fail, downshift, use the parking/emergency brake gradually, and look for an escape ramp.
Worked example
On wet pavement, a driver brakes hard and the tractor drive wheels lock. The trailer swings the tractor toward a jackknife. Correct response: release the brake pedal at once, steer in the direction of the skid to restore alignment, and once rolling, brake gently. Reasoning: locked drive wheels have little lateral grip; releasing them lets the tires roll and steer again. Holding the brake or steering harder deepens the jackknife.
Traps that cost marks
Steering against the skid; pumping ABS; keeping full brake pressure on locked wheels; overcorrecting; and using a hard stop instead of gradual slowdown after a blowout.