You have to change a tyre on the hard shoulder of the motorway. What safeguard is necessary?

You answered correctly. When you need to change a tyre on the hard shoulder of the motorway in Germany, you must set up a warning triangle in a clearly visible position about 100 meters behind your vehicle on the right edge of the lane. This alerts approaching traffic to your presence. Setting up a warning light at a sufficient distance provides additional visibility, especially in low-light or poor visibility conditions. Wearing a high-visibility vest at all times increases your safety by making you more noticeable to other road users. These precautions help prevent accidents and are required by German traffic regulations to keep both you and other drivers safe.