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, there are two separate brake circuits to ensure safety in case one fails. If one circuit leaks while driving, the air from that circuit escapes, which can significantly reduce braking power in that circuit. However, the four-way protection valve plays an important role by preventing the pressure in the intact (non-leaking) circuit from dropping below a safe level. This means the other circuit remains fully operational and maintains braking ability to stop the vehicle safely. The valve does not send extra air to the leaking circuit; it only protects the functioning circuit from losing pressure. This design ensures that even with a leak, the vehicle can still brake effectively using the intact circuit.