of their passenger equipment. One RPO car that was displayed at the 1893 World's Columbian Exposition in Chicago is one of the last known examples of the early white color scheme. As the development of passenger cars progressed, so too did the development of RPO cars. The first plans for RPO car designs were based on light baggage car frames and bodies, which sometimes resulted in catastrophe for RMS employees when the trains were involved in accidents. From 1900 to 1906 some 70 workers were killed in train wrecks while on duty in the RPOs, leading to demands for stronger steel cars. The RMS developed its first standards for car design in 1891 to address some of these issues. In 1912, the Railway Mail Service developed a set of strength requirements for new cars in an effort to push the car building companies into using steel for the cars' major structural components and underframes. The core of the requirements was that each car should be able to withstand a buffer force of at least 400,000 pounds. This requirement was doubled to 800,000 pounds in a 1938 revision of the standards. The requirements were again strengthened in 1945 with specifications that precluded the use of aluminium for framing and major structural components. The 1945 revisions also included a requirement for end posts to prevent telescoping in the event of a collision. Car manufacturers adopted these requirements and carried them through to all other models of passenger cars that they built. The 800,000 lb buffer load and end post requirements were later adopted by the Interstate Commerce Commission (ICC) for all passenger MU locomotives as of April 1, 1956 and to all passenger cars and locomotives in 1999 by the USDOT. An interesting feature of most RPO cars was a hook that could be used to snatch a leather or canvas pouch of outgoing mail hanging on a track-side mail crane at smaller towns where the train did not stop. The first US patent for such a device () was awarded to L. F. Ward of Elyria, Ohio, on January 29, 1867., about a year after apparatus for picking up and setting down mailbags without stopping was installed for equivalent UK TPOs at Slough and Maidenhead, having first been patented in UK in 1838 by Nathaniel Worsdell. With the train often operating at 70 mph or more, a postal clerk would have