Route 225 crosses the Concord River and enters the town of Bedford on Carlisle Road. At the west end of the town center, the highway joins Route 4 on North Road before the two highways join Route 62 (Concord Road) on The Great Road. Route 62 splits north onto Brookside Road and the remaining two routes cross the Shawsheen River and continue to Lexington, which they enter on Bedford Street. Route 225 and Route 4 temporarily expand to a four-lane divided highway through their cloverleaf interchange with I-95 and Route 128 (Yankee Division Highway). In the center of Lexington, the highways turn onto Massachusetts Avenue, which they follow southeast parallel to the Minuteman Bikeway through a brief concurrency with Route 2A between Marrett Road and Maple Street. Near the southeast end of Lexington, Route 225 and Route 4 turn from Massachusetts Avenue, which continues toward Arlington, onto Pleasant Street and then Watertown Street to their joint terminus at a four-ramp partial cloverleaf interchange with Route 2 (Concord Turnpike). The roadway continues south as Winter Street toward Belmont.