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Difficulty: HardStopping and Braking Procedures

A commercial driver is operating a tractor-trailer without an Antilock Braking System (ABS) on a dry, straight highway when an obstacle suddenly blocks the lane. The driver must perform emergency controlled braking to stop in the shortest distance while maintaining steering control. Which procedure correctly describes how the driver should execute controlled braking in this situation?

  1. A
    Apply the brakes fully until the wheels lock up, release the pedal completely when the vehicle begins to slide, and reapply maximum pressure once the wheels roll again.
  2. Apply the brakes as hard as possible without locking the wheels, keep steering adjustments very small, and release the brakes slightly if the wheels lock up before reapplying.Answer
  3. C
    Engage the engine retarder to maximum setting and apply light, steady service brake pressure to allow drivetrain resistance to stop the vehicle without tire lockup.
  4. D
    Brake firmly until road speed drops by 5 mph, release the brake pedal completely for several seconds to dissipate drum heat, and repeat in cycles until fully stopped.

Answer

Apply the brakes as hard as possible without locking the wheels, keep steering adjustments very small, and release the brakes slightly if the wheels lock up before reapplying.
Controlled braking is executed by applying the service brakes as hard as possible without locking the wheels. If the wheels begin to lock up or if steering corrections become necessary, the driver slightly releases the brake pressure until rolling traction is restored, then reapplies pressure. This technique achieves the shortest possible stopping distance while keeping the vehicle steerable.

Step-by-Step Solution

1
Identify the proper emergency braking technique required for rapid deceleration without sacrificing directional control on a non-ABS vehicle.
Recognize that controlled braking requires keeping tires rolling just below the threshold of locking.
Locked wheels cannot transfer side forces, resulting in immediate loss of steering response.
2
Differentiate controlled braking from other braking methods such as stab braking and snub braking.
Eliminate full-lock cycling (stab braking) and downgrade cooling cycles (snub braking).
Controlled braking maintains continuous, threshold pressure rather than cycling full lockups or intermittent cooling releases.
3
Determine the necessary driver correction if wheels begin to skid during threshold application.
Modulate the pedal by easing off slightly to restore tire rotation, then reapply firm pressure.
Releasing slight pressure unlocks the wheels and restores lateral steering traction immediately.

Key Concept

Controlled Braking Technique
Estimated Time:1m 30s
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Topics

Stopping and Braking Procedures

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