What can happen if a truck and trailer are continuously braked with the service brakes on a long downhill slope?

When a truck and trailer are continuously braked using the service brakes on a long downhill slope, several issues can arise due to excessive heat generation in the braking system.

The wheel brakes heat up significantly, leading to a condition known as brake fade. This reduces the braking efficiency, making it harder to stop the vehicle safely, which is crucial in maintaining control on steep descents.

Additionally, if the air supply to the brake system is not supplemented (which is particularly relevant for air-braked vehicles), it can result in insufficient brake pressure. This can further compromise safety as the braking system may not respond adequately when needed.

Lastly, the action of the retarder, a system designed to assist in braking, can also be diminished if the primary brakes are overused, as it may not operate effectively alongside overheated wheel brakes.

Overall, recognizing these interconnected issues is vital for safe driving practices and is emphasized in German traffic regulations to ensure that drivers are equipped to handle long descents without endangering themselves or others. In summary, all three points are relevant because they collectively address the risks associated with improper braking on downhill slopes.