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Question

Difficulty: MediumStopping and Braking Procedures

A driver operating a straight truck encounters an abrupt lane blockage on a clear roadway and decides to apply the stab braking method. Which of the following describes the correct procedure for executing this maneuver?

  1. A
    Apply firm, continuous brake pressure just below the threshold of wheel lockup while keeping steering adjustments minimal.
  2. B
    Pump the brake pedal rapidly with light pressure while shifting into neutral until the vehicle slows down.
  3. Apply the brakes all the way until the wheels lock, release the pedal completely to allow the wheels to start rolling, and reapply the brakes fully once rolling traction is restored.Answer
  4. D
    Apply steady service brake pressure while engaging the auxiliary retarder to its highest setting to maximize retardation.

Answer

Apply the brakes all the way until the wheels lock, release the pedal completely to allow the wheels to start rolling, and reapply the brakes fully once rolling traction is restored.
Stab braking requires the driver to apply the brakes fully until wheel lockup occurs, release the brake pedal completely so the wheels regain rotational traction and directional stability, and then reapply full brake pressure once the wheels are rolling again.

Step-by-Step Solution

1
Identify the distinguishing mechanism of stab braking compared to other emergency braking techniques.
Stab braking involves deliberately applying full braking force to the point of lockup, then releasing to regain steering and directional control.
Commercial vehicle emergency stopping guidelines require understanding how wheel lockup and wheel rotation interact during emergency stops.
2
Evaluate the sequence of driver actions required during the stab braking cycle.
The driver pushes the brake pedal fully down, releases it as soon as lockup occurs, waits for the wheels to begin rolling, and then reapplies full pressure.
Reapplying brakes before wheels roll prevents the vehicle from straightening out, while maintaining locked wheels causes total loss of steerability.
3
Select the option that matches the complete, correct emergency sequence.
The statement specifying full brake application, full release for rolling recovery, and reapplication matches standard FMCSA/CDL procedures.
This procedure achieves rapid deceleration while periodically restoring directional stability.

Key Concept

Emergency Braking Techniques: Controlled vs. Stab Braking
Estimated Time:1m 0s
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Topics

Stopping and Braking Procedures

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