another coupler and remained closed until opened by movement of a handle located at the side of the car.
A factor in the adoption of Janney couplers was the move toward application of air brakes for general service freight cars. Although still in the experimental stage during the 1870's and 1880's, it was apparent that some form of power braking would be used in the future. Link-and-pin couplers could not withstand the forces generated by such braking. After much testing the Westinghouse air brake was proven reliable, and many railroads began to apply it to passenger trains. It was subsequently applied to freight cars and adopted as standard equipment by the railroads. In 1893, the young Interstate Commerce Commission required by law the use of air brakes and automatic couplers on all trains engaged in interstate service. As with other standards of this period, federal and state regulation followed the lead of national railroad organizations, serving primarily as an incentive for laggard companies to move up to standards set by the better-run railroads.
It might appear that railroads in the United States were highly standardized by 1890. In certain respects they were, but much individualism remained from earlier years. Signal systems varied widely. Locomotives were designed and often built in the railroad's own shops. Each railroad set its own standards for right of way clearances, stations, bridges, tunnels, and grades. Operations conformed to the basic Standard Rules, but railroads added individual rules to suit their own needs. Many substantial differences remained between railroad companies. The railroads had recognized themselves as an industry, however, and had made important steps toward creating a truly national network of rail lines.