Route 1A is a south–north state highway in Massachusetts. It is an alternate route to U.S. 1 with three signed sections and two unsigned sections where the highway is concurrent with its parent. Due to the reconfiguration of tunnel interchanges brought on by the completion of the Big Dig, Route 1A is discontinuous in the downtown Boston area. Vehicles entering Downtown Boston via the Sumner Tunnel must take I-93 north to the exit for Government Center and make a U-turn to access the entrance ramp to I-93 south (which silently carries Route 1A south as well) and vice versa.