When are you allowed to switch on rear fog lamps?

You are allowed to switch on rear fog lamps only when fog reduces visibility to less than 50 meters. This is because rear fog lamps are very bright and can dazzle other drivers if used unnecessarily. They help make your vehicle more visible in very poor conditions such as dense fog. Using them in conditions where visibility is better, like heavy rain or when fog reduces visibility to 100 meters, is not permitted and can be dangerous or annoying to other road users. Always reserve rear fog lamps for the most severe visibility restrictions.