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Difficulty: EasyHydroplaning and Wet Road Traction Loss

During a rainstorm, oil and grease accumulate on the roadway surface and mix with water. Which of the following time periods presents the highest risk of traction loss from this slippery oil mixture?

  1. During the first few minutes after light rain starts to fallAnswer
  2. B
    After several hours of continuous heavy downpour
  3. C
    Immediately after the rain stops and the pavement begins to dry
  4. D
    Only when vehicle speeds drop below 15 miles per hour

Answer

During the first few minutes after light rain starts to fall
The correct answer highlights that oil and grease float to the surface during the first few minutes of rain, forming a dangerously slick film before prolonged rain washes the residue off the roadway.

Step-by-Step Solution

1
Identify the cause of initial wet road slipperiness
Motor oil, fuel, and grease accumulate on dry roads over time without being washed away.
Road surfaces collect hydrophobic petroleum residues during dry periods.
2
Analyze how water affects these surface deposits at the onset of rain
The first drops of rain float the oil film to the surface of the water, creating an extraordinarily slick layer.
Oil is less dense than water and floats on top before sufficient rain volume washes it onto the shoulder.
3
Select the condition with peak traction hazard
The highest hazard occurs within the first few minutes of rain falling.
Driver awareness must be highest immediately when rain begins.

Key Concept

Initial Rainfall Slickness and Traction Loss
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Topics

Hydroplaning and Wet Road Traction Loss

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