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Question

Difficulty: MediumWinter Driving

A driver is transporting freight on a shaded rural route where the ambient temperature has dropped below freezing, resulting in patches of packed snow and frosty bridge decks. Which operational adjustment should the driver perform to safely maintain control of the commercial vehicle?

  1. Turn off auxiliary engine retarders and reduce road speed by at least half.Answer
  2. B
    Keep engine retarders engaged at the highest setting to prevent service brake wear on slippery bridge decks.
  3. C
    Maintain normal highway speed while reducing following distance to remain in the clear tracks of preceding traffic.
  4. D
    Continue at posted speed limits provided the steer axle tires maintain at least 2/32 inch of tread depth.

Answer

Turn off auxiliary engine retarders and reduce road speed by at least half.
According to commercial driving safety guidelines, when driving on packed snow, speed must be reduced by at least half to account for reduced friction. Furthermore, auxiliary engine retarders must be turned off whenever roads are wet, icy, or snow-covered because applying aggressive deceleration force to only the drive wheels causes them to lose traction and trigger a dangerous drive-wheel skid or jackknife.

Step-by-Step Solution

1
Evaluate traction conditions on packed snow and frozen surfaces.
Recognize that traction is significantly reduced and braking distances are multiplied on packed snow and bridges.
Commercial vehicle stability depends directly on tire-to-road friction.
2
Adjust auxiliary deceleration systems for low-friction surfaces.
Disengage or disable auxiliary engine retarders.
Retarder braking force applied solely to drive wheels can lock them up and trigger a drive-wheel skid or jackknife on slippery pavement.
3
Apply the mandatory speed reduction for packed snow conditions.
Reduce vehicle traveling speed by at least half of the normal speed.
The commercial driver safety standard mandates cutting speed by one-third on wet pavement and by one-half or more on packed snow.

Key Concept

Speed reduction and retarder safety management on packed snow and icy roadways
Estimated Time:1m 15s
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Topics

Winter Driving

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