The 3 individual systems of the air brakes are the service brakes, emergency brake, and _________.

Air brake systems combine three braking systems: service, parking and emergency brake systems.
1. The service brake system applies and releases the brakes when you use the brake pedal during normal driving.
2. The parking brake system applies and releases the parking brakes when you use the parking brake control.
3. The emergency brake system uses parts of the service and parking brake systems to stop the vehicle in the event of a brake system failure.