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Difficulty: MediumMountain Driving, Steep Grades, and Altitude Hazards

While descending a steep mountain grade, a driver must control the vehicle's speed without causing the braking system to overheat and fail. Which braking technique should the driver use in combination with engine braking to maintain control safely?

  1. A
    Apply continuous light pressure to the brake pedal to hold a constant speed during the entire descent.
  2. Apply firm pressure to reduce speed to about 5 mph below the safe speed, release the pedal completely, and repeat when speed increases.Answer
  3. C
    Shift the transmission into neutral and pump the brake pedal rapidly to force cooling air across the brake assemblies.
  4. D
    Turn off the engine ignition periodically on straight downhill sections to allow the engine and brakes to cool down together.

Answer

The driver should apply firm brake pressure to reduce speed to about 5 mph below the safe target speed, release the pedal completely to allow cooling, and repeat the process when speed increases back to the target.
The correct technique involves shifting into a low gear before the descent and using 'snub braking'—applying firm pressure to drop speed about 5 mph below the safe limit and then fully releasing the brake pedal. This short application period slows the vehicle effectively while the release period permits vital air cooling to prevent brake overheating and fade.

Step-by-Step Solution

1
Select a lower transmission gear before starting the descent.
Engine braking (compression) bears the primary burden of controlling downhill acceleration.
Engine braking limits speed naturally without generating heat in the wheel brake components.
2
Execute snub braking whenever the vehicle accelerates to the maximum safe descent speed.
The vehicle slows down by approximately 5 mph in a short, controlled brake application.
Brief, firm braking reduces kinetic energy effectively without prolonged friction contact.
3
Completely release the brake pedal once speed is lowered.
Airflow cools the brake drums, rotors, and pads during the release phase.
Intermittent relief prevents thermal buildup that leads to fluid boiling and brake fade.

Key Concept

Engine braking and snub braking technique for steep downgrades
Estimated Time:1m 0s
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Topics

Mountain Driving, Steep Grades, and Altitude Hazards

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