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Difficulty: EasyRetarders Usage and Cautions

When driving a commercial motor vehicle on wet, icy, or snow-covered roads, which action should the driver take regarding the vehicle's retarder?

  1. A
    Keep the retarder set to maximum power to reduce wear on the service brakes
  2. Turn the retarder completely offAnswer
  3. C
    Pump the retarder switch repeatedly to simulate an anti-lock braking action
  4. D
    Engage the retarder only when traveling at speeds above 45 mph

Answer

Turn the retarder completely off
Retarders apply auxiliary braking force specifically to the drive wheels. On wet, icy, or snow-covered roads, tire traction is greatly reduced, so the braking torque from a retarder can cause the drive wheels to lose grip and start a dangerous drive-wheel skid or jackknife. Drivers must turn off retarders in these conditions.

Step-by-Step Solution

1
Identify how retarders apply braking force to a vehicle
Retarders apply auxiliary braking force only to the drive axles rather than across all wheels.
Understanding which wheels receive the retarding force is critical to evaluating vehicle stability on slippery surfaces.
2
Apply safe operating procedures for adverse road surface conditions
When roads are wet, icy, or snow-covered, drive wheels have reduced traction and can easily skid under retarder force, requiring the driver to turn the retarder off.
Switching off the retarder prevents drive-wheel lockup and jackknifing on slick pavements.

Key Concept

Retarders apply braking force to the drive wheels and must be turned off when driving on wet, icy, or snow-covered roads to prevent drive-wheel skids.
Estimated Time:45s
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Topics

Retarders Usage and Cautions

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