was discontinued in the 1930s, but the Chicago Transit Authority (CTA)'s charter continues to allow it to run funeral trains. In 1950, 6000-series cars were assigned to the Logan Square branch, which were rerouted through the Dearborn Street Subway after 1951. The Douglas branch received 6000-series cars in 1952, and both the Douglas branch and Garfield Line received 4000-series cars in 1955, at which point wooden cars were retired from the Garfield Line but kept on the Douglas branch, although by 1957 they had been retired there as well. Stations and skip-stop The stations on the main line originally consisted of two island platforms with each in between an outer track and an inner track. The sharpness of the curves of the outer tracks' bowing out to accommodate the platforms, however, was considered dangerous and some of the stations were reconfigured between 1898 and 1914. The results of these modifications varied widely by station; at Racine, it resulted in two pairs of side platforms for the northern and southern pairs of tracks, separated from one another by the Throop Street Shop, while at Halsted an island platform was placed in between the two inner tracks with two side platforms each for the outer tracks. At Marshfield, the northern platform and tracks were used for trains going to and coming from the Logan Square branch, whereas the southern platform and tracks were used for trains going to and coming from the Garfield Park and Douglas Park branches. Replacement by Congress branch A highway radiating west from downtown Chicago via Congress Street was proposed in the 1909 Plan of Chicago, which envisioned Congress as Chicago's "grand axis" and a boulevard from Grant Park to Halsted Street. The plan, which did not incorporate rapid transit into the boulevard plan, did not ultimately materialize, but provided inspiration to planners in subsequent decades. Traffic congestion was dire in cities such as Chicago by the 1920s and 1930s, especially on its west side, and superhighways were designed to alleviate it. Such highways were also designed to clear neighborhoods that were considered blighted slums. The Old Chicago Main Post Office was greatly expanded in 1932; built in the way of the proposed superhighway, it was constructed with a hole in its bottom to allow for traffic to run through it, which would be used in when the expressway was completed. The first proposal to link a Congress