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Question

Difficulty: MediumSpeed and Road Conditions

Commercial vehicle operators must adjust their driving behavior and vehicle controls to match specific traction conditions. Match each adverse road surface condition on the left with the correct mandatory safety procedure or speed adjustment on the right.

  • Wet pavement surfaceReduce operating speed by one-third (1/31/3) of the normal posted speed
  • Packed snow roadwayReduce operating speed by one-half (1/21/2) or more of the normal posted speed
  • Slippery road surface while vehicle is equipped with an engine retarderTurn off the auxiliary braking feature to prevent drive-wheel skids
  • Glare ice surfaceSlow down to a crawl and stop driving as soon as safely practical

Answer

Wet pavement surface matches with reducing speed by one-third; packed snow matches with reducing speed by one-half or more; slippery surface with an engine retarder matches with turning off the retarder; and glare ice matches with slowing down to a crawl and stopping as soon as safely practical.
Standard commercial driving safety rules establish specific actions for each road condition: wet pavement requires reducing speed by one-third; packed snow requires reducing speed by half or more; glare ice requires reducing speed to a crawl and stopping; and slippery conditions require switching off engine retarders to avoid drive-wheel skidding.

Step-by-Step Solution

1
Identify the standard proportional speed reduction rules for precipitation surfaces.
Wet roads require a one-third (1/31/3) speed reduction, while packed snow demands a reduction of one-half (1/21/2) or more.
Water and compacted snow significantly reduce tire grip, requiring proportional speed reductions to maintain safe stopping margins.
2
Determine the safety threshold for extreme low-traction surfaces like glare ice.
Glare ice mandates slowing to a crawl and finding a safe location to park.
Ice severely eliminates braking and steering friction, making highway speeds unsafe regardless of vehicle weight.
3
Apply auxiliary braking safety guidelines on reduced-traction surfaces.
Retarders and engine brakes must be turned off whenever pavement is wet, icy, or snow-covered.
Retarder forces applied solely to drive wheels can overcome available tire traction and cause instant drive-wheel lockup and jackknifing.

Key Concept

CDL Speed Adjustment Rules and Retarder Safety Under Adverse Surface Conditions
Estimated Time:1m 30s
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Topics

Speed and Road Conditions

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