Kenneth A. Browne (1905-1985) was the research director attached to the president of the Chesapeake and Ohio Railway system, on the program to develop a lightweight, low-center-of-gravity passenger train, first called the "Speedliner" but later Train "X," that would reduce costs by substituting elements of aircraft technology for traditional railroad practices.

Train "X" was the brainchild of Robert R. Young (1897-1958), a Texas-born financier who attempted to "reform" the railroad industry according to his own lights in the years between World War II and his suicide in 1958.

Although himself a wheeler-dealer of a heartland sort, Young adopted a populist stance, railing against Wall Street bankers (although he himself had an office high up in the Chrysler Building) and championing the cause of the small investor, the mythical "Aunt Jane." In the same vein, he cultivated the railroad passenger with splashy promises of better service. As someone who had worked for General Motors early in his career, Young was also impressed by the modern, thin-metal construction techniques used in the automotive and aeronautical industries. Young's multifaceted program for the railroads thus came to include expanding passenger service and increasing the level of comfort and luxury for the ordinary coach passenger and replacing the existing car stock with lightweight, mechanically efficient cars mass-produced with the latest technology.

Unfortunately, these goals were at cross-purposes. First, once the war ended, passengers began abandoning the rails for the private automobile and the airplane, so the market that Young targeted actually began shrinking drastically and irreversibly. Second, the lightweight trains he proposed turned out to be Spartan in the extreme, and when the comparison of undermaintained track and new interstate highways is taken into account, more expensive and less comfortable than a long-distance bus. Third, Young's power base was the Chesapeake & Ohio Railway, a road that reaped high profits through the prosaic job of hauling coal while serving no major passenger markets. Much more than a new type of train would be needed to achieve viable high-speed passenger rail service, and these conditions would more often be found outside the U.S. While Young had the wealth and power to force his ideas on the admittedly talent-starved railroad industry, in the end, his dreams turned out to be Quixotic.

In November 1944, Young hired Kenneth A. Browne, an engineer with a long resume in the aircraft industry, with the idea of applying up-to-date aeronautical engineering methods to what was, even by the standards of the railroad industry, a rather stodgy company. The most important project would be an ultra-lightweight passenger train employing aluminum alloys, capable of high speeds and costing less on a per-seat basis than even conventional stainless steel lightweight passenger cars. Young and Browne would be influenced by the contemporary Spanish TALGO train, being built in the U.S. by the American Car & Foundry Company. Train "X" would also employ air-cushion suspension, and single-axle running gear adapted to taking curves at speed. In 1947, Browne signed two contracts with A. A. Gassner, another accomplished aeronautical designer, doing business as Gassner Aircraft Engineering in New York. Gassner was to perform all the work to produce plans for a gas-turbine locomotive and the special cars. The Pullman-Standard Car Manufacturing Company later agreed to build the cars.

The C & O exhibited a mock-up of Train "X" cars at the Chicago Railroad Fair of 1948-1949. Pullman-Standard began work on a prototype car, but as railroad passenger traffic began dropping precipitously from its World War II high, it pulled back on its commitment, canceled Gassner's contract in 1950, and moved all work to its plant in Hammond, Ind. A single prototype car made four test runs, mostly in Michigan, in 1951-1952. At this point, the C & O, which served almost no significant passenger markets, realized that it had to interest other railroads to salvage its investment in Train "X." It received a favorable response from the New York Central, which was the nation's second-largest passenger hauler, and an industry committee was formed in 1954 to study the whole lightweight passenger train issue. The C & O and New York Central naturally favored Train "X," while the New York, New Haven, and Hartford initially favored the TALGO train, and the Pennsylvania Railroad, Baltimore & Ohio, and the Atchison, Topeka & Santa Fe, with heavier volumes and longer hauls, preferred a more conventional car (which could better accommodate food service), but with lighter construction and lower center of gravity. Eventually, each of the companies went its own way.

In the meantime, Robert R. Young won control of the New York Central in a 1954 proxy fight. The C & O contributed its research, on which it had spent about $500,000 with little practical effect, and the NYC ordered a modified version of Train "X" in 1955. The "Xplorer" began running between Cleveland and Cincinnati in the spring of 1956. Passengers found it cramped and tinny, and it rode very roughly, especially on the poorly-maintained jointed rail, and it was demoted to a short life in Chicago commuter service the following year. The New Haven ordered a bi-directional Train "X" called the "Dan'l Webster" for service between New York and Boston with similar results.

Although Train "X" was a failure, some of its features were incorporated in later versions of high-speed trains, although much of the research and development would be done outside the United States.