were designed by railroad and Westinghouse engineers and tried on the West Jersey & Seashore Railroad track. From these tests the DD1 class was developed. The DD1s were used in pairs (back-to-back). Thirty-three of these engines having Westinghouse equipment were built at Altoona. They were capable of speeds up to . Placed in service in 1910, they performed well, lasting in regular service through the 1940s. Steel suburban passenger cars capable of being electrified for MU operation were designed due to the need for such cars in service to Penn Station through its associated tunnels and were designated MP54. Designs for corresponding cars accommodating baggage and mail were produced also. Eight of these cars were electrified with DC equipment to provide shuttle service from Penn Station to Manhattan Transfer between 1910 and 1922. More extensive electrification plans required AC electrification, starting with 93 cars for the Paoli Line in 1915. With the expansion of the AC electrification, additional MP54 cars were electrified or purchased new until a total of 481 cars was reached in 1951. Replacement with newer types of cars began in 1958 and the last MP54 cars were retired in the early 1980s. The single FF1 appeared in 1917 and ran experimentally for a number of years in preparation for electrification over the Allegheny Mountains that never came to fruition. Its AC induction motors and side-rod drive powered six axles. It developed a starting tractive force of , which was capable of ripping couplers out of the fragile wooden freight cars in use at the time. In 1924, another side-rod locomotive was designed: (the L5 class). Two DC locomotives were built for the New York electrified zone and a third, road number 3930, was AC-equipped and put in service at Philadelphia. Later 21 more L-5 locomotives were built for the New York service. A six-wheeled switching engine was the next electric motive power designed, being classified as B1. Of the first 16 AC engines, two were used at Philadelphia and 14 on the Bay Ridge line, while 12 DC-equipped engines were assigned to Sunnyside Yard in Queens, New York. The O1 class was a light passenger type. Eight of these engines were built from June 1930 to December 1931. The P5 class was also introduced, with two of this class being placed in service during July and August 1931. Following these came the P5A, a slightly heavier design