to Everett Atlantic Avenue Elevated (closed 1938), from the Washington Street El at the Castle Street Wye at Herald Street (Tower 'D') to the Charlestown El and Causeway Street El at North Station (Tower 'C') Common user rail network Unlike the subway, which is owned and operated by the MBTA, the common user network is owned and operated by a mixture of various public and private sector bodies. In the Boston area, trackage is owned by a mixture of the MBTA and several freight railroads. Commuter rail services are operated by the Keolis Commuter Services (KCS) under contract to the MBTA, intercity passenger services are operated by Amtrak, and freight services are operated by the various freight railroads. Trackage rights allow trains of one operator to make use of tracks owned by another. Commuter rail The MBTA commuter rail system brings people from as far away as Worcester and Providence (Rhode Island) into Boston. There are approximately 125,000 one-way trips on the commuter rail each day, making it the fifth-busiest commuter rail system in the country, outranked only by the various systems serving New York and Chicago suburbs. There are two major rail terminals in Boston: North Station and South Station. Commuter rail lines from the North Shore and northwestern suburbs begin and terminate at North Station; lines from the South Shore and the west start and end at South Station. There is no direct rail connection between North Station and South Station, so that interchange between the two stations generally requires the use of two different subway lines (Red/Orange or Red/Green). However, passengers on commuter lines serving Back Bay Station can interchange directly from there to North Station using the Orange Line, and passengers on the Fitchburg Line can interchange directly from Porter to South Station using the Red Line. Intercity rail Boston is served by four intercity rail services, all operated by Amtrak. The Acela and Northeast Regional services both operate on the Northeast Corridor to and from Washington, D.C., with stops in places such as New York City and Philadelphia. A branch of the Lake Shore Limited service operates to and from Chicago. The Downeaster service operates to and from Brunswick, Maine. The Northeast Corridor services terminate at South Station, as does the Lake Shore Limited. The Downeaster service terminates at North Station, primarily because the Downeaster Amtrak line is intended for points north of downtown. The