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Question

Difficulty: EasyHot Weather Driving

While driving a commercial motor vehicle on a highway during extreme summer heat, you observe spots where tar is rising to the surface of the asphalt pavement. How does this condition affect driving safety?

  1. A
    It rapidly strips away tire rubber, instantly reducing steer tire tread depth below the legal minimum.
  2. It makes the pavement surface very slippery, significantly reducing tire traction.Answer
  3. C
    It requires engaging the engine retarder at maximum power to maintain drive-wheel grip.
  4. D
    It requires applying sudden, hard braking to force the tires through the soft tar layer.

Answer

Tar rising to the surface ('bleeding tar') makes the pavement very slippery, reducing available tire traction.
In very hot weather, tar in the road pavement frequently softens and bleeds to the surface. These tar spots become very slick, greatly reducing tire traction and increasing the hazard of skidding.

Step-by-Step Solution

1
Identify the physical change that occurs in asphalt pavement during hot weather.
Intense pavement heat causes the tar binder in the road mixture to melt and bleed to the surface.
High ambient and surface temperatures liquefy asphalt components, pushing them upward.
2
Assess the effect of surface tar on vehicle traction and control.
The exposed tar creates slick spots that significantly lower the coefficient of friction under the tires.
Reduced friction makes the road surface slippery, increasing stopping distances and skid potential.

Key Concept

Hot weather road surface hazards and tar bleeding traction reduction
Estimated Time:45s
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Topics

Hot Weather Driving

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