Beginning in the 1920s many streetcar lines in Brooklyn and the rest of the city began to be replaced by buses, particularly after the unification of the city's three primary transit companies (including the BMT) under municipal operations in June 1940. The New Lots Avenue Line was converted to buses in mid-1941, running from the Canarsie Depot at Rockaway Avenue and Hegeman Avenue continuing east along Hegeman Avenue and Linden Boulevard to Atkins Avenue/Berriman Street in East New York. The service was assigned the B10 designation. On July 8, 1947, the B10 was extended to replace Sumner Avenue trolley service. The Sumner route was cut back from Williamsburg Bridge Plaza to its current terminal at Broadway and Sumner Avenue with direct Bedford–Stuyvesant-Red Hook service unreplaced. Sumner trolley service was fully eliminated in 1949.