 In 1956, the Canadian provinces and U.S. states came to an agreement with the American Association of Motor Vehicle Administrators, the Automobile Manufacturers Association and the National Safety Council that standardized the size for licence plates for vehicles (except those for motorcycles) at in height by in width, with standardized mounting holes.These figures may vary slightly by jurisdiction.Smaller-sized plates are used for motorcycles and, in some jurisdictions, mopeds and certain types of trailers and construction equipment.