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Question

Difficulty: MediumSkid Control and Recovery

A tractor-trailer is descending a slippery downgrade with the engine retarder active when the drive wheels suddenly lose traction and begin to slide sideways. Which action should the driver take immediately to regain directional control?

  1. A
    Steer firmly in the opposite direction of the rear slide while applying the trailer hand valve to pull the combination straight.
  2. Turn off the engine retarder immediately, stay off the brakes, and steer in the direction the vehicle needs to go.Answer
  3. C
    Keep the retarder engaged to preserve engine braking force and apply firm, continuous pressure to the service brakes.
  4. D
    Lock the service brakes fully and counter-steer toward the high side of the road slope.

Answer

Turn off the engine retarder immediately, stay off the brakes, and steer in the direction the vehicle needs to go.
When drive wheels skid on a slippery road due to retarder torque, the first essential step is to switch off the retarder and stay off the brakes so the wheels can regain rotational grip. The driver must then steer in the direction the vehicle needs to go and counter-steer as the vehicle straightens to prevent a secondary slide.

Step-by-Step Solution

1
Eliminate the source of drive-wheel braking torque by switching off the retarder and releasing all brakes.
The drive wheels are allowed to roll freely again rather than being dragged across the slick road surface.
Tires must roll in order to generate the lateral traction necessary for directional control.
2
Turn the steering wheel smoothly in the direction the vehicle needs to travel, followed by counter-steering as the vehicle straightens.
The front wheels align the tractor with the intended lane of travel and prevent a secondary skid in the opposite direction.
Steering in the direction of intended travel realigns the front and rear axles.

Key Concept

Drive-wheel skid recovery and retarder safety on slippery surfaces
Estimated Time:1m 0s
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Topics

Skid Control and Recovery

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