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Zorluk: OrtaMountain Driving and Steep Downgrades

An operator of a heavy combination vehicle is approaching the crest of an unfamiliar 7-mile, 6% mountain downgrade. Which procedure should the driver execute to safely manage vehicle speed before and during the descent?

  1. A
    Remain in the current cruising gear and apply continuous, gentle pressure to the service brake pedal to prevent the vehicle from gaining momentum.
  2. B
    Activate the auxiliary engine retarder at maximum capacity throughout the descent, regardless of whether the roadway surface is wet or slippery.
  3. Shift into a gear lower than the gear needed to climb the hill before starting down the grade, relying on engine compression as the primary braking force.Cevap
  4. D
    Crest the hill in top gear and perform a double-clutch downshift once gravity causes the truck to exceed the established safe speed.

Cevap

Shift into a gear lower than the gear needed to climb the hill before starting down the grade, relying on engine compression as the primary braking force.
Selecting a low gear before beginning the descent ensures that the vehicle relies primarily on engine compression braking to control speed. Because modern trucks have lower rolling resistance and aerodynamic drag, drivers must often shift into a gear lower than the gear used to climb the hill. Service brakes should only serve as a supplement through proper snub braking.

Adım Adım Çözüm

1
Determine the proper gear and safe speed before reaching the crest of the downgrade.
A safe descent speed is established based on gross vehicle weight, length and steepness of grade, and road conditions.
Speed and gear selection must always occur before gravity accelerates the vehicle.
2
Downshift the transmission into a low gear prior to starting down the descent.
The engine provides primary retarding power through compression braking.
Modern aerodynamic trucks freewheel easily, requiring a lower gear than used to climb the same grade.
3
Use service brakes only as a secondary supplement to engine braking.
Brakes remain cool and retain full stopping capability in an emergency.
Service brakes cannot dissipate the massive heat generated if used as the primary holding mechanism on long descents.

Anahtar Kavram

Pre-descent gear selection and the principle of engine braking as primary speed control on mountain downgrades.
Tahmini Süre:1m 15s
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Mountain Driving and Steep Downgrades

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