High Quality Content by WIKIPEDIA articles! The North–South Rail Link is a proposed pair of approximately 1.5 mile (2.4 km)-long rail tunnels below downtown Boston, Massachusetts. The tunnels would serve the goals of better unification for Boston`s separate northern and southern MBTA Commuter Rail terminals, and provide direct linkage between Amtrak`s southerly service to Washington D.C. and its northeastern service to Portland, Maine. The Amtrak Downeaster line from Maine, arriving from the north, has no direct connection to Amtrak`s Northeast Corridor carrying the Acela service to points south, or to the Lake Shore Limited service to points west. Both Amtrak and the commuter rail networks terminate at North and South Stations. The proposed tunnels would span the gap between the two termini.