What happens when air pressure in the system drops below a certain level?

When the air pressure in the braking system drops below a certain level, spring brakes will engage. This is a critical safety feature in heavy commercial vehicles equipped with air brake systems. The spring brakes are designed to activate automatically when air pressure falls to a predetermined threshold.

This mechanism ensures that even in the event of air pressure loss—whether due to a leak or other failure—the brakes can still function to safely stop the vehicle, preventing potential accidents. Engaging the spring brakes helps secure the vehicle in place, particularly if it is parked on an incline or in other hazardous conditions. This design is fundamental in maintaining control and ensuring driver and public safety on the road.