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Difficulty: HardSpeed and Road Conditions

A commercial motor vehicle is traveling at 54 mph54\text{ mph} on a divided highway when a sudden downpour creates standing water along the travel lanes. The driver observes the steering wheel feeling abnormally light with minimal resistance and notices that water spray from the tires has ceased. Which sequence of actions must the driver take to regain vehicle control and adjust to the road conditions?

  1. A
    Engage the engine retarder to maximum power to decelerate the drive axles while making rapid steering corrections to find pavement grooves.
  2. Release the accelerator pedal without braking, maintain a straight steering path until the tires regain road contact, and subsequently reduce speed to approximately 36 mph36\text{ mph}.Answer
  3. C
    Apply the service brakes firmly to shorten the vehicle's total stopping distance and rely on antilock braking to restore steering control on standing water.
  4. D
    Maintain current speed until approaching the next highway curve, then apply firm brake pressure while turning to stabilize the chassis.

Answer

Release the accelerator pedal without braking, maintain a straight steering path until the tires regain road contact, and subsequently reduce speed to approximately 36 mph36\text{ mph}.
The correct response requires releasing the accelerator pedal without braking or retarder use, allowing the tires to regain direct contact with the road surface. Once control is established, the commercial driver must apply the standard wet-road speed adjustment rule by reducing speed by approximately one-third, bringing the initial 54 mph54\text{ mph} down to 36 mph36\text{ mph}.

Step-by-Step Solution

1
Identify the signs of hydroplaning from the scenario context.
Light steering feel and diminished tire spray indicate that the tires are riding on a thin film of water rather than contacting the pavement.
Recognizing hydroplaning early is essential to avoid actions that trigger an immediate spin or skid.
2
Select the proper recovery procedure for hydroplaning.
Ease off the accelerator pedal, do not apply service brakes, push in the clutch if operating a manual transmission, and keep the steering wheel steady until the tires penetrate the water film and regain grip.
Braking or engaging an engine retarder while hydroplaning locks the wheels and prevents them from cutting through the water.
3
Calculate the safe operational speed for a wet road surface according to CDL guidelines.
On a wet road, reduce speed by about one-third: 54 mph−(13×54 mph)=54 mph−18 mph=36 mph54\text{ mph} - \left(\frac{1}{3} \times 54\text{ mph}\right) = 54\text{ mph} - 18\text{ mph} = 36\text{ mph}.
Commercial vehicles require approximately one-third speed reduction on wet surfaces to maintain traction and prevent further hydroplaning.

Key Concept

Hydroplaning dynamics, safe recovery controls, and the standard one-third speed reduction rule on wet road surfaces.
Estimated Time:1m 30s
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Topics

Speed and Road Conditions

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