Platforms at IRT Broadway–Seventh Avenue Line stations between and , including those at 137th Street, were lengthened to in 1948, allowing full ten-car express trains to stop at these stations. The platform extensions at these stations were opened in stages. On April 6, 1948, the platform extension at 137th Street opened. Simultaneously, the IRT routes were given numbered designations with the introduction of "R-type" rolling stock. These fleet contained rollsigns with numbered designations for each service. The first such fleet, the R12, was put into service in 1948. The route to 242nd Street became known as the 1. In 1959, all 1 trains became local.