What happens if one of the service brake circuits of a dual-circuit compressed air-braking system leaks when the vehicle is in motion?

In a dual-circuit compressed air-braking system, if one of the service brake circuits develops a leak while the vehicle is in motion, it can lead to a significant reduction in braking effectiveness. The first choice correctly states that the air supply from the leaking circuit will escape, which diminishes braking action.

The second choice is also correct because the four-way protection valve plays a crucial role in maintaining safety. It protects the intact circuit from losing pressure below the required safety threshold, ensuring that at least one braking circuit remains operational.

Understanding that the four-way protection valve does not supply air to the leaking circuit, as suggested by the third choice, is essential. This valve is designed to maintain the pressure in the functioning circuit rather than compensating for losses in the defective one.

These mechanisms are vital for ensuring vehicle safety on the road and are outlined in German traffic regulations, emphasizing the need for reliable braking systems and the importance of proper vehicle maintenance. Recognizing all relevant options in such scenarios is crucial to comprehending the system's function and ensuring safe driving practices.