Association of American Railroads (AAR)

The Association of American Railroads (AAR) is the central trade and standards-setting body for the North American freight railroad industry. Its member railroads include the major Class I carriers of the United States, Canada, and Mexico, along with many smaller railroads and associate members. The AAR's defining role is to publish and maintain the technical and operating standards that allow freight cars to move seamlessly across different railroads' lines, a process known as interchange.

The AAR was formed on October 12, 1934 through the consolidation of several predecessor trade organizations. These included the American Railway Association (and its later expanded form, the American Railroad Association), the Association of Railway Executives, the Bureau of Railway Economics, and accounting and treasury officer associations. Through this lineage the AAR also inherited the mechanical-standards tradition of the historic Master Car Builders' Association.

Much of the AAR's technical work is carried out through standing committees that maintain the interchange rules, equipment specifications, and billing procedures governing freight equipment. The organization publishes the Field Manual and Office Manual of the Interchange Rules and administers the system of reporting marks used to identify rail equipment.

The AAR operates subsidiaries that support these functions, including Railinc, which provides IT and data services, and the research and testing organization historically operated as Transportation Technology Center, Inc.

Learn more on the AAR website: https://www.aar.org/