Warning Flag The DVLA at Swansea is sending out warning letters to drivers as follows: "In order to assist other motorists in identifying potentially dangerous drivers, it is now compulsory for anyone with a lower than average driving ability and intelligence to display a warning flag. The flag (comprising of a red cross on a white background) will be attached to the top of at least one door of their vehicle. For drivers of exceptionally low ability, additional flags are required."