CDL General Knowledge TestDriving SafelyMedium
A commercial driver is operating a vehicle with a manual transmission on a long, steep downgrade. To effectively control their speed and prevent brake fade, what is the most appropriate action?
- AShift to a lower gear than what is needed to climb the grade.
- BEngage the clutch and coast down the grade, applying brakes only when necessary.
- CMaintain a high gear and apply continuous, light brake pressure.
- DShift to neutral and rely solely on the foot brake for speed control.
Show answer & explanationAnswer & explanation
Correct answer: A. Shift to a lower gear than what is needed to climb the grade.
Shifting to a lower gear than what is needed to climb the grade allows the engine to provide significant braking power, reducing the reliance on the service brakes and preventing them from overheating and fading.
Why the other options are wrong
- B. Coasting is illegal and extremely dangerous as it removes engine braking and puts all stress on the service brakes.
- C. Continuous light braking overheats the brakes, leading to brake fade.
- D. Shifting to neutral removes engine braking entirely, relying solely on service brakes, which is dangerous.
Safe Mountain Descent
The technique of using a low gear and intermittent braking to safely control vehicle speed on long, steep downgrades, preventing brake fade.
- Select a gear that keeps the engine RPMs high enough to provide braking.
- This gear should be lower than what's needed to climb the same grade.
- Use 'snub braking' – firm, short applications of the service brakes.
Memory trick: Downhill, low gear, save your brake gear.