When does the braking action of a trailer with overrun brakes start?

In the case of trailers equipped with overrun brakes, the braking action begins when the trailer is pushed forward by the vehicle it is attached to. Specifically, this occurs when the trailer runs up to the truck. It is essential that this braking action coincides with the truck's braking to maintain stability and prevent any form of jarring or discontinuity in braking response between the truck and the trailer. This ensures that both the truck and trailer respond cohesively when stopping.

The other options involve either the activation of the truck's brake pedal or a sequence where the trailer's brakes engage before the truck's action, which can lead to an uncoordinated braking event. Understanding this sequence is crucial for ensuring road safety and effective control while towing, as laid out in German traffic regulations.