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CDL · Emergencies

If your drive wheels (tractor) begin to skid and the tractor starts to jackknife, what should you do?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

Stop braking (release the brakes) to let the drive wheels regain traction and roll, then steer to maintain control

  1. A Brake harder
  2. B Stop braking (release the brakes) to let the drive wheels regain traction and roll, then steer to maintain control
  3. C Accelerate hard
  4. D Turn the wheel sharply

Why this is the answer

If the tractor DRIVE WHEELS skid and the tractor begins to JACKKNIFE (the tractor swings relative to the trailer), you should STOP BRAKING (release the brakes) to let the drive wheels regain traction and roll again — rolling wheels can grip and steer, allowing you to regain control; then steer to keep the vehicle straight. CDL combination.

The cause: locked/skidding drive wheels lose traction and the tractor can swing. RELEASING the brakes lets the wheels roll and regain traction (the counterintuitive but correct action). SAME PRINCIPLE applies to trailer skids (release brakes to let the trailer wheels roll and come back in line).

Prevention: smooth, gradual braking; slow down for curves and conditions; don't over-brake. Knowing to release the brakes to recover from a drive-wheel skid/jackknife is commonly tested and safety-critical.

Source: FMCSA CDL Manual — Combination, Tractor Jackknife Recovery

Practice more questions

This question is from our CDL Practice Tests practice test. Take the full practice test to test your knowledge across all Emergencies and other topics.

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About this topic: Emergencies

Emergencies in a combination vehicle escalate faster than in a straight truck: a trailer can jackknife, roll, or lose air to its brakes. These questions cover trailer skids, emergency braking with a trailer, air-line failures and how the tractor protection valve behaves when the trailer loses pressure. This is one of 3 Combination Vehicles questions on emergencies, each with a full explanation on a single study page.

New to this exam? Our CDL exam guide explains the format, scoring, and how to prepare.

Related questions

Emergencies

If the trailer wheels begin to skid and the trailer starts to swing out (trailer jackknife), what should the driver do?

 Emergencies

To prevent a trailer skid (and possible jackknife), what is the most important driving practice?

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