While driving a truck, when do you have to turn off the rear anti-fog lights?

In accordance with the provisions of the Road Traffic Act, rear fog lights, the activation of which is indicated by the warning light shown in the picture, may only be used when visibility is reduced to less than 50 m. In the event of improved visibility, the driver is required to switch these lights off immediately. An increase in visibility to 60 metres means that the condition for their use is no longer met.