Budd–Michelin rubber-tired rail cars remained obscure in comparison with other competitors for the title, such as the "Pioneer Zephyr" and Union Pacific's M-10000. Rubber-tired rail cars achieved greater success in France, and similar rubber-tired subway cars have been adopted in Canada and Mexico as well as on numerous systems in Europe. During the 1920s, the American Budd Company, at the time a relatively obscure auto-frame supplier, developed an extensive working relationship with the French firm Michelin, which was best known for its tires. In 1929, Michelin built its first rail car, and by 1932 nine of its cars were in operating service, all of
Synthetic rubber researchers created in 1940. B. F. Goodrich Company scientist Waldo Semon developed a new and cheaper version of synthetic rubber known as Ameripol in 1940. Ameripol made synthetic rubber production much more cost effective, helping to meet the United States' needs during World War II. The production of synthetic rubber in the United States expanded greatly during World War II, since the Axis powers controlled nearly all the world's limited supplies of natural rubber by mid-1942.Military trucks needed rubber for tires, and rubber was used in almost every other war machine. The U.S. government launched a major (and largely secret)