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Zorluk: OrtaMountain Driving and Steep Downgrades

A tractor-trailer with a gross combination weight of 75,000 lbs is navigating a 4-mile descent on a 6% grade. The driver establishes a safe maximum speed of 35 mph. Under standard commercial vehicle snub braking guidelines, which action correctly manages vehicle speed on this downgrade?

  1. A
    Apply light, continuous brake pressure to hold the speed steadily at exactly 35 mph throughout the descent.
  2. Apply the service brakes firmly enough to reduce speed to 30 mph, release them completely, and reapply when speed reaches 35 mph.Cevap
  3. C
    Shift the transmission into neutral to coast between brief cycles of heavy braking whenever speed exceeds 40 mph.
  4. D
    Allow the vehicle momentum to increase to 45 mph before applying maximum threshold braking down to 20 mph.

Cevap

Apply the service brakes firmly enough to reduce speed to 30 mph, release them completely, and reapply when speed reaches 35 mph.
The proper snub braking technique requires applying the service brakes firmly until speed drops 5 mph below the established safe speed, then releasing them completely to allow the brake components to cool until speed rises back to the safe threshold.

Adım Adım Çözüm

1
Establish the safe maximum operating speed based on the vehicle load, road grade percentage, and highway conditions.
Safe maximum speed is determined to be 35 mph.
Setting an explicit safe speed defines the upper boundary where braking intervention must begin.
2
When vehicle speed reaches the safe speed of 35 mph, apply the service brakes with enough force to feel a definite slowdown.
Vehicle speed drops to 30 mph in approximately three seconds.
Firm application slows the combination vehicle quickly without prolonged continuous contact.
3
Release the service brakes completely once the vehicle slows to 5 mph below the safe speed (30 mph).
Brakes release and the vehicle gradually accelerates back toward 35 mph under engine braking while the brake drums cool.
Releasing the brakes allows airflow to dissipate thermal energy from the drums and linings between applications.

Anahtar Kavram

Snub braking technique for mountain downgrades
Tahmini Süre:1m 0s
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Konular

Mountain Driving and Steep Downgrades

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