The conversion from streetcar to bus operation came from great pressure applied by New York City's Board of Transportation for a unified bus transportation system across the city. TARS applied for its first bus franchises in 1928. By 1948, all streetcar lines in Manhattan and The Bronx were converted to bus operation. The lines in Westchester County continued to operate, until the Yonkers city lines were shut down in 1952. Third Avenue Railway was purchased by New York City Omnibus Corporation in 1956, and transferred the remaining transit operating franchises to subsidiary Surface Transportation, Inc.