What does the "spring brake" do in air brake systems?

The "spring brake" in air brake systems serves two essential functions: it acts as a parking brake and provides emergency braking. This is crucial for safety and vehicle control. When the air pressure in the system drops to a specific level, often due to a leak or malfunction, the spring brake automatically engages. It utilizes powerful springs that apply the brakes, holding the vehicle stationary even on inclines.

Additionally, in the case of an emergency, if the primary air supply fails, the spring brakes will engage to stop the vehicle. This dual role is vital, as it ensures that air brake systems can still maintain effective braking capability in situations where normal braking pressure is compromised. Other options, such as enhancing air circulation or adjusting brake pads, do not accurately reflect the primary purpose of the spring brake in air brake systems, which is to secure the vehicle and provide a backup braking method.