CDL General Knowledge TestCombination Vehicles (if applicable)Hard
You are driving a combination vehicle and experience a 'trailer jackknife' during emergency braking on a slippery road. What is the most effective immediate action to recover from this situation?
- ASteer sharply into the skid to align the trailer.
- BRelease the service brakes and steer gently in the direction of the skid.
- CRelease the service brakes and gently apply the trailer hand valve.
- DApply more power to the drive wheels to pull the trailer straight.
Show answer & explanationAnswer & explanation
Correct answer: B. Release the service brakes and steer gently in the direction of the skid.
If the trailer begins to jackknife, the most crucial action is to release the service brakes immediately. This allows the trailer wheels to roll freely again, reducing the over-braking that caused the skid. Then, steer gently in the direction the trailer is skidding to help straighten out the combination. Applying the trailer hand valve or more power would worsen the situation.
Why the other options are wrong
- A. Steering sharply can worsen the jackknife or lead to loss of control of the tractor.
- C. Applying the trailer hand valve (trolley valve) would apply the trailer brakes even harder, worsening the jackknife.
- D. Applying power to drive wheels might spin them on a slippery surface and complicate recovery, not straighten the trailer.
Trailer Jackknife Recovery
To recover from a trailer jackknife, release the service brakes to allow the trailer wheels to roll freely, then steer gently to straighten the vehicle.
- Caused by trailer wheels locking up.
- Release brakes to regain traction.
- Gentle steering is key to control.
Memory trick: Release and ease, then steer to please.