In the event of losing air pressure in the emergency system, which action should be expected?

When air pressure is lost in the emergency braking system of a combination vehicle, the primary safety feature designed to protect against total brake failure is the automatic activation of the trailer brakes. This system relies on the fact that an air-powered trailer brake system is equipped with a mechanism that activates the brakes when it detects a drop in air pressure, thereby minimizing the risk of uncontrolled movement of the trailer. This is a critical safety measure to ensure that even if there is a failure in the braking system, the trailer can still maintain control and stop safely.

This automatic application of the trailer brakes helps to maintain stability and control of the entire combination vehicle, allowing the driver to handle the situation more safely until they can pull over or stop the vehicle completely. Thus, this response is crucial for preventing accidents and ensuring safety on the road.