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

The braking action of a trailer with overrun brakes begins when the trailer runs up to the truck. This is because the overrun braking system relies on the kinetic energy of the trailer pushing against the hitch mechanism of the towing vehicle. When the truck's brakes are applied, the trailer is pushed forward, which engages its braking system.

While it's essential to recognize that the brake pedal in the truck does initiate the braking process overall, for trailers equipped with overrun brakes, the initial braking action is a result of this interaction. Thus, it is important to consider the complete mechanism rather than just the truck's brake activation alone.

Understanding this combination ensures safe towing practices and proper functioning of trailer brakes, as stated in German traffic regulations, which aim to prevent accidents caused by improper understanding of trailer braking dynamics.