Michigan CDL - Air Brakes Practice Exam

What should you do when traveling down a steep downgrade?

1. Shift into a higher gear and rely on brakes

2. Shift into a lower gear and use brakes to supplement engine braking

3. Maintain speed without shifting gears

4. Only use brakes without shifting gears

The correct answer is: Shift into a lower gear and use brakes to supplement engine braking

When traveling down a steep downgrade, shifting into a lower gear is essential because it allows for better engine braking. Engine braking occurs when you reduce the throttle and the engine slows the vehicle down through its compression resistance. This natural slowing effect helps to lessen the reliance on the vehicle's braking system, which can overheat and fade if used excessively. By shifting into a lower gear, you engage the drivetrain more effectively, allowing the engine to assist in controlling the vehicle's speed as you go downhill. Using the brakes to supplement this process helps maintain a safe speed without risking brake failure due to overheating. It's a crucial part of maintaining control and ensuring safety on steep grades. The other options would generally lead to reduced control over the vehicle while descending steep hills, putting both the driver and other road users at risk.