What are spring brakes used for in vehicles with air brakes?

Spring brakes serve a crucial role in vehicles equipped with air brake systems, specifically for parking and emergency braking purposes. These brakes utilize a spring mechanism that engages when the air pressure in the brake system drops below a certain level, such as when the vehicle is turned off or in case of a failure in the air system. This automatic engagement provides a reliable way to secure the vehicle in place when parked, ensuring it does not roll away.

In the event of an emergency, should the primary air pressure be lost while driving, the spring brakes will activate, helping to bring the vehicle to a stop. This dual function of providing both parking and emergency braking is vital for vehicle safety, particularly in larger commercial vehicles that may not stop as quickly as smaller vehicles.

The other choices focus on different functionalities not directly related to the primary purpose of spring brakes. For instance, enhancing fuel efficiency, assisting in traction control, and reducing wear on regular brakes do not align with the essential role spring brakes play in maintaining the safety and stability of a vehicle in parked and emergency situations.