A commercial driver is preparing to descend a steep mountain grade covered with packed snow. What is the correct sequence of actions the driver must take to maintain vehicle control and complete the descent safely?
- 1Turn off the engine retarder or auxiliary braking system.
- 2Reduce vehicle speed and shift into a transmission gear lower than the gear used on dry pavement before starting down the hill.
- 3Proceed down the grade using engine compression to maintain a speed at least one-third lower than the normal dry-road speed.
- 4Apply light, smooth service brake pressure only when needed to prevent speed buildup, releasing as soon as target speed is restored.
Cevap
The correct sequence is: first, turn off the engine retarder; second, reduce speed and downshift to a lower gear before starting down the hill; third, proceed down the grade using engine compression at a reduced speed; fourth, apply light, smooth service brake pressure only as needed to prevent speed buildup.
On slippery winter surfaces such as packed snow, the driver must first switch off engine retarders to avoid drive-axle skidding. Next, the vehicle must be slowed and downshifted into an appropriate low gear before the descent begins, as downshifting while descending on slick pavement can cause loss of gear engagement and control. Once on the grade, engine compression must be used to hold a speed reduced by at least one-third, with gentle, supplemental service braking used only when necessary to regulate speed without locking the wheels.
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Anahtar Kavram
Safe descent procedures and speed management on snow-covered downgrades require disabling retarders, downshifting prior to the descent, and relying on engine braking with gentle snub braking.
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