The MBTA Commuter Rail system serves as the commuter rail arm of the Massachusetts Bay Transportation Authority's (MBTA's) transportation coverage of Greater Boston in the United States. Trains run over of track to 134 stations. It is operated under contract by Keolis, which took over operations on July 1, 2014, from the Massachusetts Bay Commuter Railroad Company (MBCR). In , the system had a ridership of , or about per weekday as of , making it the sixth-busiest commuter rail system in the U.S., behind the three New York-area systems, the Chicago-area system, and the Philadelphia-area system. The line's characteristic purple-trimmed coaches operate as far south as North Kingstown, Rhode Island, and as far north as Newburyport and as far west as Fitchburg, both in Massachusetts. Trains originate at two major terminals in Boston – South Station and North Station. The only connection between the two halves of the system is the non-revenue Grand Junction Branch. The North–South Rail Link is a proposed tunnel between North Station and South Station to allow through-running service. Service Lines The system consists of twelve lines – four of which have branches – radiating from downtown Boston. Eight "southside" lines terminate at South Station, with four (Framingham/Worcester, Needham, Franklin/Foxboro, and Providence/Stoughton) also running through Back Bay station. Four "northside" lines terminate at North Station. The Kingston Line and Middleborough/Lakeville Line are often grouped together as the Old Colony Lines. The lines vary in length from the Fairmount Line to the Providence/Stoughton Line, with typical lengths in the range. The system has of revenue trackage and covers roughly the eastern third of Massachusetts plus central Rhode Island. Most lines do not share trackage outside the Boston terminal areas, with several exceptions. The Providence/Stoughton Line and Franklin/Foxboro Line both use the Northeast Corridor between and South Station, with the Needham Line also sharing the tracks between and South Station. The Old Colony Lines and the Greenbush Line all use the Old Colony mainline between South Station and . The Haverhill Line and Newburyport/Rockport Line share tracks between North Station and near . A small number of Haverhill Line trains use the inner Lowell Line and the Wildcat Branch, while a small number of Franklin/Foxboro Line trains use the Fairmount Line rather than the Northeast Corridor. Several Amtrak intercity routes run on MBTA tracks: the and over the Providence/Stoughton Line, the over the Framingham/Worcester Line, and the