Abstract The author establishes the several basic objectives motivating introduction of Train X, and presents in digest form a description of the more important design features calculated to meet these objectives, including a discussion of single-axle suspension, automatic coupling, structure, acoustic treatment, and so on. He lays particular stress on the importance of cost reduction (initial, operating, and maintenance) and emphasizes the extent to which design was influenced by this factor and the need to provide maximum passenger comfort and acceptance.