When one vehicle is towing another vehicle, the drawbar or other connection shall be of sufficient strength to pull all weight towed thereby and such drawbar or other connection shall not exceed fifteen feet from one vehicle to the other except the connection between any two vehicles transporting poles, pipe, machinery or other objects of structural nature which cannot readily be dismembered. When one vehicle is towing another vehicle and the connection consists of a chain, rope or cable there shall be displayed upon such connection a white flag or cloth not less than twelve inches square.