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Interstate 93 begins in the south at exit 12 of I-95 in Canton. I-93 begins co-signed with U.S. Route 1 North. At this junction, I-95 North heads to the northwest (co-signed with U.S. Route 1 South, as well as Route 128, which begins at the interchange), to serve as the beltway around Boston, while I-95 South runs by itself southwest through Boston's southwestern suburbs toward Rhode Island.
The first few miles of I-93 run east through Boston's southern suburbs, passing through Canton and Randolph. In Randolph, I-93 meets the northern end of Route 24 (Fall River Expressway/AMVETS Memorial Highway) at Exit 4. I-93 continues east into Braintree, interchanging with Route 3, the major freeway linking Boston to Cape Cod, at Exit 7 (known locally as the "Braintree Split"). Route 3 North joins I-93 and US-1, and the highway turns north toward Boston.

Signs in the Financial District of Boston point toward Downtown Crossing, Chinatown, Interstate 93, and Interstate 90.
Upon turning northward, the highway is known as the Southeast Expressway through Quincy, Milton and Boston's Dorchester section. After the Massachusetts Avenue connector exit, the highway officially becomes the John F. Fitzgerald Expressway, which is also known as the Central Artery, and passes beneath downtown Boston. A major intersection with the Massachusetts Turnpike/Interstate 90 (Exit 20) takes place just south of downtown Boston. After the massive interchange, motorists use the Thomas P. O'Neill Jr. Tunnel to travel underneath the city and then use Zakim Bunker Hill Bridge to cross the Charles River. Two exits are located in the tunnel, where the speed limit is 45 miles (72 km) an hour. Route 3 leaves the Artery just before the Zakim bridge via Exit 26, and U.S. Route 1 leaves the Artery just after the bridge, via Exit 27 (no southbound access). From Boston through the rest of Massachusetts, Concord, NH appears as the control city on northbound overhead signs. The Artery ends as I-93 continues north out of the city.
I-93 continues through the northern suburbs of Boston, coming in Woburn to a second intersection with Interstate 95 and Route 128, which run in a concurrency. Travelers going north can either change over to I-95 north to eventually reach Maine, or remain on I-93 toward New Hampshire. Farther north, in Andover, I-93 meets I-495, providing access to Worcester to the southwest and New Hampshire's seacoast region to the northeast. Just south of the state line, I-93 crosses the Merrimack River into Methuen, where it interchanges with Routes 110 and 113 at exit 46 just north of the river crossing, where Routes 110 and 113 junction with I-93 at a rotary to be replaced with a partial cloverleaf beginning in mid-2013, with the old rotary set to be demolished in early 2017.[7] I-93 then interchanges with the western end of Route 213, a connector between I-93 and I-495. I-93 then crosses into New Hampshire after about a mile.
In all, I-93 has 48 numbered exits in Massachusetts, although several numbers are skipped in and near Boston. One noteworthy reason that some exits were removed from I-93 is to further address traffic problems in addition to converting the Central Artery from six to eight to ten lanes, by reducing the combined number of on- and off-ramps from 27 to 14.[8] Exit 48 in Methuen, just before the New Hampshire state line, is the highest-numbered exit along the entire route. I-93 once had only 22 exits prior to the re-routing of I-95 onto MA 128.[9] Due to the highway being one of the two major Interstates that enter Boston directly (Interstate 90 is the other), nearly the entire length of the highway in Massachusetts carries four lanes in each direction. Average daily traffic volumes on I-93 in the state range from 100,000 vehicles at the New Hampshire border[10] and 150,000 vehicles at the southern end at I-95[11] to over 200,000 vehicles through Braintree and Quincy.[10]