How do you differentiate between service brakes and the parking/emergency brake on an air-brake bus?

• A. Parking/emergency brake locks wheels and holds the bus when stationary
• B. Service brakes slow/stop during driving
• C. Both brake types operate identically
• D. Only braking when stationary

Answer: (A)

On an air-brake bus, two braking systems serve different jobs. The service brakes are what you use while driving—the brake pedal sends air to the brake cylinders to slow and stop the bus during movement. The parking/emergency brake, on the other hand, is spring-applied and air-released; its purpose is to hold the bus in place when parked by locking the wheels, and it also acts as an emergency backup if the service brakes fail. So you differentiate them by function and mechanism: the parking/emergency brake locks wheels and holds the bus stationary, while the service brakes slow or stop the bus during driving. The other options either describe braking occurring only when stationary or claim both brakes work identically, which doesn’t reflect their distinct roles.