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

The statement is true because on long, steep downgrades, the primary method for controlling speed should be engine braking, which helps to prevent overheating of the brake system and reduces the risk of brake failure. Engine braking occurs when the driver shifts to a lower gear, allowing the engine to hold back the vehicle's speed through compression, which is a more effective and safer method of maintaining control on descents.

While brake usage will still be necessary at times, it is intended to be a supplementary measure rather than the primary means of slowing down. This is particularly important to prevent excessive wear on the brake components, which can lead to brake fade if they are continuously applied on long descents. By relying primarily on engine braking, drivers can help ensure that their brakes remain effective throughout the entire descent.

In terms of other options, they introduce additional conditions that complicate this fundamental principle without changing the essential fact that brakes should primarily serve as a support mechanism, rather than the main control method on steep grades.