In which cases must you activate the release valve?

To understand when to activate the release valve, it's important to know the function of each option related to trailer braking systems in German traffic rules. The release valve is primarily used when the air tanks are full and the brake lines are disconnected. In this case, activating the valve allows the trailer to be moved safely without setting off the parking brake.

Additionally, activating the release valve before setting off is crucial for ensuring that the air tanks of the trailer can adequately fill and that the parking brake can be released. Not activating it in these situations can lead to issues like the inability to move the trailer or improper braking, which can be dangerous on the road.

Thus, the correct combination of activating the release valve must include all scenarios where it impacts the safe operation of the vehicle. Understanding this helps in ensuring compliance with German traffic regulations and enhances overall road safety.