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Question

Difficulty: HardSpeed and Road Conditions

When a commercial motor vehicle encounters standing water and begins to hydroplane, the driver should apply light service brake pressure or activate the engine retarder to help the tires maintain contact with the road surface.

Answer: Answer

Answer

False. Drivers must never apply brakes or activate engine retarders during hydroplaning, as this locks the drive wheels and causes an immediate skid or jackknife. Instead, the driver should release the accelerator and depress the clutch to allow the vehicle to slow down naturally until traction is regained.
The statement is false because applying service brakes or activating auxiliary retarders while hydroplaning removes rolling wheel traction, precipitating drive-wheel lockup and severe loss of directional control. Safe commercial vehicle operation dictates easing off the accelerator and depressing the clutch without braking until tires regain mechanical adhesion.

Step-by-Step Solution

1
Analyze the physical dynamics of hydroplaning on water-covered roadways.
Hydroplaning creates a dynamic water wedge that lifts tires off the pavement surface, reducing the coefficient of friction between tire rubber and the roadway to near zero.
Understanding traction loss mechanisms explains why normal control inputs behave unpredictably.
2
Evaluate the mechanical consequence of applying service brakes or retarders during hydroplaning.
Because available surface friction is insufficient to overcome brake torque, any brake or retarder application causes immediate wheel lockup, eliminating rotational stability and steering capability.
Drive-wheel lockup on slippery surfaces directly induces trailer swing or tractor jackknife.
3
Identify the standard commercial driver procedure for hydroplaning recovery.
The driver must avoid the brake pedal, release the throttle, and disengage the driveline to allow rotating tires to displace standing water and re-establish pavement contact.
Rolling wheels displace water through tread grooves much more effectively than locked, sliding wheels.
4
Determine the truth value of the presented statement.
The assertion that light braking or retarder use helps maintain road contact is false and contradicts critical safety regulations.
Braking exacerbates hydroplaning instability rather than correcting it.

Key Concept

Hydroplaning dynamics, traction preservation, and prohibition of braking or retarder use on standing water.
Estimated Time:1m 30s
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Topics

Speed and Road Conditions

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