and three in the other. After the interchange with the Massachusetts Turnpike, just before the route enters the Tip O'Neill Tunnel in Downtown Boston, it is reduced to six lanes. The Southeast Expressway segment of Route 3 is approximately 10 miles long. While in Downtown Boston, Route 3 is concurrent with I-93 and US-1. Route 3 exits I-93 at Exit 18, passes through Leverett Circle, and runs for a short way along the Charles River to the Longfellow Bridge, where it crosses over to Cambridge and joins Memorial Drive. On Memorial Drive, at an interchange with Route 2A, the designation of the highway changes to U.S. Route 3, which continues through Boston's northern suburbs and toward New Hampshire. History Route 3 began as a new designation for New England Highway 6 in 1927 when the U.S. Highway system was created and New England highway Route 3 was chosen to be US 6. The former NE 6 then took the route 3 number with U.S. Route 3 designated north of its intersection with U.S. Route 1 and Massachusetts Route 3 to the south. The route was basically a connected system of two-lane roadways up until the 1950s with the exception of Route 3's original path through Boston which paired it with US 1 on Park Drive, the Riverway and the Jamaicaway and then along its own path in Mattapan and Dorchester along the Arborway, Morton Street and Gallivan Boulevard. Before the road was rerouted, the road continued over the Cape Cod Canal via the Sagamore Bridge to the Bourne Rotary, to the south of the Bourne Bridge. This arrangement changed after 1951. The Plimoth Plantation Highway, a two-lane expressway that connects Route 3 with Route 3A, was once signed as Route 3 before the southernmost portion of the freeway to Cape Cod was finished. The first section of the Pilgrims Highway was built as a bypass of Plymouth in the early 1950s. The mid-1950s saw an extension of this bypass route south to the Sagamore Bridge and north to Kingston. The northern section of the highway was built next with a connection from Derby Street in Hingham to the Southeast Expressway opening in 1959. (Portions of this road run alongside the Old Colony Railroad's mainline, now used by the MBTA Old Colony Lines Commuter Rail, and the MBTA Red Line's Braintree Branch rapid transit.) Finally the last sections between Hingham and