In the 1940s most railroad freight car wheels had solid journal bearings, but many newer passenger cars and locomotives were using roller bearings. At the 1948 Railroad Fair the Timken Roller Bearing Company of Canton, Ohio, exhibited a demonstration "Roller Freight" car utilizing the company's famous tapered roller bearings (not visible, however, in this transparency). Today all equipment in revenue service that is interchanged between railroads is required to have roller bearings.