there are no US regulations on rear fog lights
European regulations require at least one rear fog light and it has to be at the side of the vehicle that faces opposite traffic... two rear fog lights are allowed which allows the vehicle to be legal on either right hand or left hand traffic systems
European regulations require at least one rear fog light and it has to be at the side of the vehicle that faces opposite traffic... two rear fog lights are allowed which allows the vehicle to be legal on either right hand or left hand traffic systems