The Standard Carrier Alpha Code CD contains ASCII files listing of transportation-providing firms and their unique Standard Carrier Alpha Codes.  Also included are special alpha codes specifically designed to identify privately owned railroad cars, freight containers, and intermodal chassis and trailers.  SCAC is a unique two-to-four letter code assigned to transportation companies for identification purposes. It is required for EDI, intermodal interchange agreements, U.S. Customs entry, when doing business with many shippers, on rate tariffs filed with regulatory agencies, government bills of lading, and on bids for government traffic. Supplements are issued quarterly and the directory is reissued annually. Each CD contains a master file containing all active SCACs, a supplement file containing those SCACs added, cancelled and changed since the last quarter and a file containing the record layout. SCAC is copyrighted by the National Motor Freight Traffic Association, Inc.