Policeman with flashing helmet. Night drivers may soon be able to identify policemen on traffic duty by a flashing blue light on their helmets. Derby police are experimenting with the idea aimed at making point - duty men more easily seen after dark. The light , which has been developed by Rolls Royce Ltd., of Derby , has a power pack contained in a haversack which is carried on the Constables ' s back. Inspector Fletcher , head of the Traffic Department said he can see no reason why it should not be adopted on a nationwide scale but the invention would have to be approved by the Ministry of Transport before it could be brought into use. Photo shows ; A policeman with a flashing blue light on his helmet , checks over the power pack contained in his haversack. 2 January 1964