Williamsburg Bridge), which change direction at Chambers Street, every service has one north end and one south end. On the 42nd Street Shuttle, railroad north is compass west, due to the line's former status as part of the main line. In fact, very few track connections exist to allow a train to reverse railroad direction without running around a loop or literally reversing direction by backing up. The IND system (except on the ex-LIRR Rockaway Line) has none of these; this philosophy may explain the lack of track connections between parallel IND lines at Seventh Avenue in Manhattan and Hoyt–Schermerhorn Streets in Brooklyn. Before unification, all BMT lines ran east–west, west being towards Manhattan. After unification, west became north and east became south. History This nomenclature has been complicated by the differing systems and cultures of the former private companies that operated parts of the system, by the need for non-ambiguous names in a city where there are stations with the same name on different lines in different locations and even different boroughs, and by changing perceptions of the best way to communicate information to a diverse public. Up until 1940, there were three major operators of New York subway and elevated lines, the privately owned Brooklyn–Manhattan Transit Corporation (BMT), the privately owned Interborough Rapid Transit Company (IRT) and the municipally-owned Independent Subway System (ISS or ICOS before 1940, now IND). Service labels have always been assigned based on their outer line (Brooklyn on the BMT, Bronx on the IRT and IND) and then by the Manhattan trunk if necessary to distinguish multiple services on the same line. BMT The BMT was the inheritor of subway, elevated and surface rapid transit lines that had been built in Brooklyn and Queens by a variety of previous operators, mainly surface steam railroads to Coney Island and elevated railroads in more populated areas. The BMT identified most of its lines by the common names given to them, often going well back into the 19th century. Services on these lines usually had the same name as the branch line they operated on; for example, the line that the current F service runs on in Brooklyn was (and is) the Culver Line, and the BMT signed these trains Culver Local or Culver Express. Partly as a result of its steam railroad history, BMT terminals were far more likely to be named after neighborhoods or towns,