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Question

Difficulty: HardSpeed and Road Conditions

When driving on wet or icy road surfaces, engaging an engine retarder helps prevent drive-wheel lockup by distributing supplemental braking force evenly across all tractor and trailer axles.

Answer: Answer

Answer

False
The statement is false because auxiliary retarders (engine brakes, exhaust brakes, hydraulic retarders, or electric retarders) apply retarding forces only to the drive wheels rather than distributing braking torque across all vehicle axles. On wet, snowy, or icy pavement where road friction is already severely degraded, this concentrated drive-axle drag can cause the drive tires to break traction and lock up, rapidly initiating a drive-wheel skid or vehicle jackknife. Commercial drivers are instructed to turn off all retarders whenever road conditions become slippery.

Step-by-Step Solution

1
Identify the mechanical application of braking forces generated by engine retarders
Engine retarders deliver retarding resistance exclusively to the drive axle wheels, not to steer or trailer axles
Understanding how auxiliary braking systems interact with specific vehicle axles is required to evaluate vehicle dynamics
2
Analyze how reduced tire-to-road friction on wet or icy surfaces responds to drive-wheel retarding torque
The localized drag on the drive wheels easily exceeds available tire traction, causing drive tires to slide
Tire adhesion limits on low-friction road surfaces cannot sustain additional non-braked wheel drag without losing lateral and longitudinal stability
3
Apply official commercial driving safety procedures for adverse road conditions
Auxiliary retarders must be disabled whenever roads are wet, icy, or snow-covered
Disabling retarders prevents sudden drive-wheel lockup and catastrophic vehicle jackknife

Key Concept

Engine retarder operation and drive-wheel traction limits on low-friction road surfaces
Estimated Time:1m 0s
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Topics

Speed and Road Conditions

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