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Difficulty: HardSkid Control and Recovery

A commercial motor vehicle operating at highway speeds encounters a stretch of roadway covered in standing water during a heavy downpour. The driver experiences a sudden drop in steering resistance alongside a slight rise in engine RPM without an increase in road speed, confirming that the vehicle is hydroplaning. What is the most appropriate action the driver must take to safely recover control?

  1. A
    Engage the auxiliary engine retarder immediately to slow the drive axle without activating the foundation brakes.
  2. B
    Apply firm, steady service brake pressure to rapidly reduce forward momentum before directional drift occurs.
  3. Ease off the accelerator pedal smoothly without braking and maintain straight tracking until tire traction is restored.Answer
  4. D
    Counter-steer vigorously back and forth across the lane to force the steer tire sipes to channel water away.

Answer

Ease off the accelerator pedal smoothly without braking and maintain straight tracking until tire traction is restored.
When hydroplaning occurs, the tires ride on a layer of water and lose direct contact with the pavement. The only safe recovery technique is to release the accelerator pedal smoothly, avoid braking, and keep the steering wheel steady. This allows the vehicle to coast down until vehicle weight and tire tread displacement overcome water pressure and restore traction.

Step-by-Step Solution

1
Identify the loss of physical tire-to-road contact.
Recognize that hydrodynamic lift has separated the tire tread from the pavement surface, eliminating steering and braking friction.
Hydroplaning occurs when water pressure ahead of the tire exceeds wheel load, lifting the contact patch off the road.
2
Remove drive torque without introducing braking forces.
The vehicle coasts smoothly, allowing speed to drop gradually without inducing wheel lockup.
Applying either service brakes or retarders can instantly lock spinning or floating wheels and produce an unrecoverable skid.
3
Maintain directional heading with minimal steering input.
As velocity decreases, water pressure under the tires drops, permitting the tread to reconnect with the pavement.
Keeping the wheels pointed along the vehicle path prevents violent lateral weight transfer and loss of control when traction abruptly returns.

Key Concept

Hydroplaning Recovery and Prevention of Drive-Wheel Lockup

Alternative Method

If driving a manual transmission commercial vehicle where engine drag causes noticeable deceleration upon throttle release, depressing the clutch pedal can fully disconnect driveline drag to maintain pure freewheeling until steering resistance returns.
Estimated Time:1m 30s
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Topics

Skid Control and Recovery

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