What will be the effect if the brake line hose with the yellow coupling head tears between the towing vehicle and trailer during braking?

The correct combination of answers (1 and 2) reflects the safety measures in place for braking when a tear occurs in the brake line hose.

1. The four-way protection valve ensures that the towing vehicle's service brake system maintains pressure. This is crucial because it allows the vehicle to still have braking power even if there's an issue with the trailer.

2. Simultaneously, the automatic venting of the supply line leads to the trailer being braked. This is a critical safety feature that prevents the trailer from becoming uncontrollable if there is a failure in the braking system.

Together, these responses highlight the importance of maintaining control and safety in emergency situations, as outlined in German road safety regulations. Understanding how these systems work is key to safe towing practices.