Standardization
Because of the physical and mental demands placed on RPO clerks, the Railway Mail Service pushed the adoption of standardized floor plans and fixtures for all RPO cars, with the first plans published in 1885. The RMS also pressed for improved lighting fixtures to help the clerks see the addresses on the mail they sorted, first by improving the reflectors in the 1880s, then calling for discontinuance of oil lamps in the 1890s and the first experiments with electric lighting in 1912. Clerks' safety was also of great concern to the RMS, with the first comprehensive statistics on work-related injuries published in 1877.
Through the second half of the 19th century, most RPO cars were painted in a somewhat uniform color scheme regardless of the railroad that owned or operated them. Most were painted white with trim in either buff, red or blue, which made the cars stand out from the other cars. By the 1890s, this practice had waned as railroads painted their RPO cars to match the rest 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. 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.
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 (U.S. Patent 61,584) was awarded to L.F. Ward of Elyria, Ohio, on January 29, 1867. With the train often operating at 70 mph or more, a postal clerk would have a pouch of mail ready to be dispatched as the train passed the station. In a co-ordinated movement, the catcher arm was swung out to catch the hanging mail pouch while the clerk stood in the open doorway. As the inbound pouch slammed into the catcher arm, the clerk kicked the outbound mail pouch out of the car, making certain to kick it far enough that it was not sucked back under the train. An employee of the local post office would retrieve the pouch and deliver it to the post office.
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Chicago, Burlington and Quincy Railroad #1923, a heavyweight RPO preserved at the Illinois Railway Museum.
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The interior of an RPO on display at the National Railroad Museum in Green Bay, Wisconsin.
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A close-up view of the mail hook on CB&Q #1923.
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A view of the mail hook on GN #42, along with a track-side mail crane complete with mail bag.
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Belfast & Moosehead Lake RR #15 RPO, Belfast, ME 1947
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