The R10 was the first series of post-war New York City Subway cars. They were built by the American Car and Foundry Company from 1948 to 1949 for the IND/BMT B Division. A total of 400 cars were built, arranged as single units. Two versions were manufactured: Westinghouse (WH)-powered cars and General Electric (GE)-powered cars. The R10s introduced many innovations, including an all-welded low-alloy high tensile (LAHT) steel construction, dynamic braking, improved propulsion, and various cosmetic features. The first R10s entered service on November 20, 1948. Various modifications were made over the years to the R10 fleet, and about 110 cars were lightly overhauled in 1984–1986. Some R10s were replaced by the R46s in the late 1970s; the remaining cars, despite having low reliability rates, outlasted several newer car classes. The remaining R10s were replaced by the R68s and R68As and last ran on October 29, 1989. Two cars have been preserved, while the rest were scrapped. Description The R10s were originally numbered 1803–1852 and 3000–3349. Cars 1803–1852 were renumbered 2950–2999 in 1970. As the first series of post-war subway cars, the R10s introduced many innovations. For the first time, the car body was of an all-welded low-alloy high tensile (LAHT) steel construction. This gave the body great strength, as the body and underframe were welded together to form a single, durable, and rigid car body, which had strong structural integrity. The R10s also featured a new type of braking system known as the "SMEE" schedule braking, which introduced dynamic braking. Dynamic braking reduced wear and tear on brake shoes, reducing maintenance costs. Improved propulsion, in the form of four traction motors design, instead of the traditional two motors (the setup used in the Arnines), improved acceleration from 1.75 mph per second to the current 2.5 mph/s. They also featured roofline side destination signs, an arrangement that drew criticism. The R10s were also the first subway cars to incorporate roller bearings, instead of the standard friction bearings found on all older railway stock, as well as being the last subway cars ordered with air-operated door engines. Additionally, the R10s were the first subway cars to be equipped with air horns, as opposed to the air whistles that were found on all pre-war subway cars. Finally, the cars introduced the General Steel Industries cast steel truck frame design also used on many passenger cars and coaches up until the R68As in