What must you do to prevent a two-axle bus from rolling down a slope?

To prevent a two-axle bus from rolling down a slope, it is essential to use a combination of safety measures. Engaging the parking brake ensures that the bus remains stationary by applying a consistent force to the braking system, which is a fundamental requirement according to German traffic law.

Placing a wheel chock under a rear wheel adds an extra layer of safety by physically blocking the wheel and preventing any potential movement if the parking brake fails. This practice aligns with German traffic regulations that emphasize the importance of preventing vehicles from rolling when parked, especially on inclines.

Using just one of these measures may not provide sufficient safety, which is why choosing both is necessary to comply with the regulations and ensure the vehicle is secured properly.