What is unique about vehicles like buses concerning their air systems?

Vehicles like buses have a unique characteristic when it comes to their air systems; they are equipped with a separate air tank that is dedicated specifically for spring brakes. Spring brakes are an essential safety feature in heavy vehicles, including buses, as they provide a reliable method of stopping the vehicle if air pressure in the primary braking system fails.

In a typical setup, this separate air tank helps maintain adequate pressure for the spring brakes. The spring brakes are engaged when the vehicle is parked to ensure it remains stationary, and they automatically activate if the air pressure drops below a certain threshold. This design is critical for safety, as it allows the vehicle to remain secure even if issues arise with the main braking system.

Understanding the separate air tank's function highlights its importance in the overall braking system of larger vehicles like buses, which are subject to different operational needs and safety regulations compared to smaller vehicles.