A flatbed commercial truck carrying a gross vehicle weight of approaches a warning sign indicating an upcoming , grade on dry asphalt. Before reaching the crest of the hill, what primary action must the driver take regarding gear selection, and how should service brakes be utilized during the descent?
- AShift into the lowest gear only after descending into the grade, then apply continuous light pedal pressure to maintain a uniform downhill speed.
- Downshift to a gear lower than the gear required to climb the hill before starting down the grade, then use snub braking to slow below safe speed each time safe speed is reached.Cevap
- CShift the transmission into neutral to eliminate engine drag, relying on firm service brake applications only when the vehicle exceeds the maximum highway speed limit.
- DUpshift one gear higher than climbing gear before cresting to preserve forward momentum, then pump the service brakes rapidly whenever vehicle speed rises.
Cevap
Downshift to a gear lower than the gear required to climb the hill before starting down the grade, then use snub braking to slow 5 mph below safe speed each time safe speed is reached.
The driver must select an appropriate low gear—typically lower than the gear needed to climb the hill—before beginning the descent because engine braking must be the primary method of controlling speed. As vehicle speed accelerates to the determined safe speed, the driver must apply the service brakes firmly enough to drop speed by (taking about seconds), and then release the brakes completely to allow heat dissipation. Repeating this cycle prevents brake overheating and ensures steady control.
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Anahtar Kavram
Low gear selection prior to downgrade cresting and proper snub braking application
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