You want to drive a vehicle with a trailer equipped with overrun braking. What do you have to check before beginning the journey?

The correct combination includes checking that the connecting device is locked, ensuring the lighting system is functioning properly, and confirming that the breakaway cable is attached. Each of these checks is crucial for safe trailer operation.

1. **Connecting Device**: Ensuring it is locked prevents the trailer from disconnecting while driving, which is essential for safety.

2. **Lighting System**: Proper functioning lights are vital for visibility and communication with other road users. Malfunctioning lights can lead to accidents or traffic violations.

3. **Breakaway Cable**: This safety feature ensures that if the trailer detaches from the towing vehicle, the brakes are applied to prevent further movement, reducing the risk of accidents.

Together, these checks align with German traffic regulations aimed at maintaining safety on the roads. Ensuring that all three aspects are addressed helps prevent accidents and ensures compliance with legal requirements for towing vehicles.