In the United States, most railroads have only two rail directions. In this vein, all New York City subway lines are deemed to run north–south. In many cases, this is close to the related compass direction, but this is not always possible. Any line that enters Manhattan from the Bronx or Queens heads south into Manhattan; any line entering Manhattan from Brooklyn goes north into Manhattan, with the BMT Nassau Street Line and BMT Canarsie Lines being the only exception, as the Nassau Street Line heads further south into Manhattan's Financial District after entering Manhattan over the Williamsburg Bridge, and the Canarsie Line goes neither north nor south. Directions of other lines are determined by following the services that run over them; except for the BMT Eastern Division services (over the 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.