In the event of brake system failure, the emergency brake system uses _____ to stop the vehicle?

• A. The emergency air reservoir
• B. The hydraulic booster
• C. The exhaust brake
• D. Parts of the service brake and parking brake

Answer: (D)

The emergency brake is a back-up system that uses components from both the service brakes and the parking brake to stop the vehicle. In a brake failure, you still have the hardware that actually presses the brake shoes against the drums or discs—the same parts used by the regular brakes—plus the parking brake mechanism that can apply those brakes without relying on the normal air pressure supply. This combination lets you slow or stop the vehicle even when the primary braking system isn’t functioning. The other options aren’t how the emergency brake operates: the emergency air reservoir isn’t an active braking actuator, the hydraulic booster helps with pedal effort but isn’t the emergency brake, and an exhaust brake is a separate engine braking feature not part of the standard emergency stopping system.