Are you allowed to use the rear fog lights if the fog restricts visibility to a distance less than 50 m?

In the photo you are driving along a road with barriers in thick fog, which hides the section of the roadway further ahead. When fog limits visibility to less than 50 m, you are allowed to use rear fog lights. The answer is: yes.

The Road Traffic Act states that the driver of a vehicle may use rear fog lights if visibility is reduced to less than 50 m, and when visibility improves, the driver must switch these lights off immediately. In such thick fog, ordinary rear position lights can be seen only from a dozen or so metres away, which is too late for the driver behind you to brake in time; a rear fog light is many times brighter and cuts through the fog. You switch them on together with dipped headlights or front fog lights, drive slowly, with a large following distance, and remember to switch them off when the fog thins - then they start to dazzle the drivers behind. A distance of 50 m is easy to judge using the edge marker posts, which outside built-up areas usually stand every 100 m.

Legal basis: Art. 30 para. 3 and para. 1 point 1 letter a of the Road Traffic Act (Prawo o ruchu drogowym)