Question

Difficulty: HardSpeed and Road Conditions

A commercial driver is operating a loaded combination vehicle at 60 mph on a highway when a sudden downpour creates standing water in the wheel ruts along a roadway section leading into a curve. Which set of operational actions must the driver take to safely manage vehicle speed and control under these road conditions?

  1. A
    Engage the engine retarder on high to reduce service brake heat, maintain 50 mph, and apply hard braking if the steer tires begin to hydroplane.
  2. B
    Maintain 60 mph until reaching the curve apex, then brake firmly while steering through the standing water to preserve forward momentum.
  3. Reduce speed by approximately one-third to about 40 mph before entering the curve, turn off the engine retarder, and ease off the accelerator without hard braking if hydroplaning occurs.Answer
  4. D
    Reduce speed by only 5 mph while maintaining dry following distance, relying on trailer service brakes to achieve standard dry stopping distance.

Answer

Reduce speed by approximately one-third to about 40 mph before entering the curve, turn off the engine retarder, and ease off the accelerator without hard braking if hydroplaning occurs.
On wet pavement with standing water, commercial drivers must reduce speed by at least one-third (from 60 mph down to approximately 40 mph) before reaching a curve. Furthermore, engine retarders must be disabled to prevent drive-wheel skids on slick surfaces, and any hydroplaning event must be handled by easing off the accelerator rather than applying hard brakes.

Step-by-Step Solution

1
Calculate required wet surface speed reduction
Speed is lowered from 60 mph to approximately 40 mph (a 1/3 reduction)
CDL regulations mandate reducing speed by at least one-third on wet pavement to account for reduced tire traction.
2
Adjust vehicle controls for slippery surfaces
Engine retarder is switched off
Retarders apply braking force to drive axles only, which can cause wheel lockup and jackknifing when road traction is poor.
3
Manage curve entry and potential hydroplaning
Decelerate before the curve and release the accelerator smoothly if steering feels light
Braking must occur in a straight line before entering curves, and hydroplaning recovery requires releasing throttle without abrupt braking.

Key Concept

Speed and traction management on wet and slippery roadways
Estimated Time:2m 0s
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