True or False: The use of brakes on a long, steep downgrade is only a supplement to the braking effect of the engine.

The statement is true because, when descending a long, steep downgrade, the primary braking force comes from engine braking, which utilizes the engine's compression to help slow the vehicle down. This method is particularly effective in maintaining control and preventing overheating of the brakes, which can occur if they are overused on steep grades.

Using the brakes is indeed supplementary, as relying solely on brake systems can lead to brake fade due to excessive heat build-up. Engine braking reduces reliance on the brakes, thereby enhancing safety and extending the lifespan of the braking system. This principle is crucial for drivers of heavy commercial vehicles, where maintaining control on downgrades is vital for safety.

While some may think the effectiveness of brakes varies by vehicle type, the fundamental concept remains that engine braking serves as the primary means of controlling speed on steep downgrades, with brakes acting as a backup.