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Question

Difficulty: MediumMountain Driving and Steep Downgrades

A commercial driver operating a loaded combination vehicle is approaching a mountain summit with a mandatory brake inspection turnout prior to descending a steep 6%6\% grade. Place the following procedures in the correct chronological order from summit arrival through descent initiation.

  1. 1Stop in the designated summit brake check area to inspect the brake system components and verify air pressure.
  2. 2Review posted road signs to evaluate the slope percentage, length of the grade, and posted safe maximum speed.
  3. 3Reduce speed and shift into the appropriate low gear before the vehicle crests the top of the hill.
  4. 4Cross the crest and begin the descent at or below the safe speed, relying on engine compression braking as the primary retarder.

Answer

The correct chronological sequence is: first, stop in the summit turnout to inspect brake components; second, review posted signs to evaluate the grade and safe speed; third, reduce speed and shift into a low gear before cresting the hill; and finally, begin the descent at or below the safe speed using engine braking as the primary retarder.
Safe mountain driving requires a strict procedural order: verifying brake adjustment and pressure at the summit turnout, assessing downgrade signs to establish the safe speed, shifting into the proper low gear prior to cresting the hill, and initiating the descent using engine compression braking to maintain control.

Step-by-Step Solution

1
Conduct a summit brake inspection at the designated turnout
Brake adjustment, mechanical integrity, and air pressure are verified before encountering gravity on the downgrade.
Summit check areas allow drivers to detect mechanical faults or low pressure before starting down steep grades.
2
Assess the downgrade steepness, length, and safe descent speed
The target safe speed is determined based on total vehicle weight, road surface, and hill geometry.
Gear selection and safe speed calculations must match the specific grade characteristics and cargo weight.
3
Slow down and shift into the proper low gear prior to cresting
The transmission is locked into the correct low gear before gravity begins accelerating the vehicle.
Downshifting after starting down a steep grade is unsafe and often impossible due to driveline torque.
4
Initiate the descent using engine compression braking as the primary speed control
The vehicle descends smoothly at or below the safe speed without overheating the foundation brakes.
Engine braking preserves the service brakes for emergency snub applications and prevents brake fade.

Key Concept

Chronological procedure for mountain summit preparation, pre-crest gear selection, and downgrade initiation.
Estimated Time:1m 30s
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Topics

Mountain Driving and Steep Downgrades

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