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Question

Difficulty: MediumStopping and Braking Procedures

A commercial motor vehicle driver traveling at highway speed encounters a sudden roadway obstruction and must execute an emergency stop while maintaining full directional steering control. When utilizing the controlled braking technique, which procedure should the driver follow?

  1. A
    Apply the brakes hard enough to lock all wheels completely, then release the pedal only after the vehicle begins to skid.
  2. Apply the brakes as hard as possible without locking the wheels, keeping any necessary steering wheel movements very small.Answer
  3. C
    Apply firm braking pressure until road speed drops 5 mph below the safe speed, then release the pedal completely until speed increases.
  4. D
    Engage the auxiliary engine retarder to maximum power while rapidly pumping the service brake pedal up and down.

Answer

Apply the brakes as hard as possible without locking the wheels, keeping any necessary steering wheel movements very small.
Controlled braking is defined in standard commercial motor vehicle operation as applying the service brakes as hard as possible without locking the wheels. If steering adjustments must be made, they must be kept very small, as heavy steering while applying maximum brake pressure can induce a skid.

Step-by-Step Solution

1
Identify the primary goal of controlled braking during an emergency stop.
The driver must achieve maximum deceleration while preventing wheel lockup to retain steering control.
When commercial vehicle tires lock up, they lose lateral traction, rendering the steering wheel ineffective and inducing skids or jackknifing.
2
Differentiate controlled braking from stab braking and downgrade snub braking.
Controlled braking applies smooth, maximum friction without locking wheels, whereas stab braking locks wheels and releases, and snub braking is for downgrade thermal management.
Controlled braking allows continuous steering adjustment throughout the entire deceleration event.
3
Select the correct application technique according to CDL standards.
Press the brake pedal as hard as possible without wheel lockup, making only very minor steering corrections if needed.
Excessive or aggressive steering inputs during maximum threshold braking can destabilize the vehicle combination.

Key Concept

Controlled Braking Technique in Emergency Situations
Estimated Time:1m 0s
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Topics

Stopping and Braking Procedures

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