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Difficulty: EasySpeed and Road Conditions

You are operating a commercial motor vehicle at a posted speed limit of 55 mph55\text{ mph} when a steady rain makes the road surface wet. According to commercial driving safety standards, how should you adjust your speed to maintain safe control?

  1. A
    Maintain 55 mph55\text{ mph} and turn on the engine retarder to assist the drive wheels with automatic braking.
  2. Reduce your speed by about one-third, slowing down to approximately 35 mph35\text{ mph}.Answer
  3. C
    Maintain 55 mph55\text{ mph} during travel and apply firm, continuous brake pressure only after entering curves or turns.
  4. D
    Maintain 55 mph55\text{ mph} because wet pavement does not increase perception or reaction distance.

Answer

Reduce your speed by about one-third, slowing down to approximately 35 mph35\text{ mph}.
According to the official CDL manual, drivers must reduce their speed by about one-third on a wet road (for example, slowing from 55 mph55\text{ mph} down to approximately 35 mph35\text{ mph}) to account for decreased tire traction and avoid hydroplaning.

Step-by-Step Solution

1
Identify the prevailing road condition and current operating speed.
The road surface is wet from rain, and the baseline speed is 55 mph55\text{ mph}.
Safe commercial vehicle operation requires matching speed adjustments directly to road surface traction.
2
Apply the official CDL speed reduction rule for wet pavement.
Reduce speed by 1/31/3: 55 mph×(1−1/3)≈35 mph55\text{ mph} \times (1 - 1/3) \approx 35\text{ mph}.
Wet roads reduce tire friction, increasing stopping distances and creating hydroplaning hazards unless speed is reduced by roughly one-third.

Key Concept

Speed adjustment on wet road surfaces
Estimated Time:45s
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Topics

Speed and Road Conditions

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