Southeast Expressway The Southeast Expressway was constructed between 1954 and 1959, at the same time the
John F. Fitzgerald Expressway (Central Artery) was built. Its northern terminus is at exit 15 (southbound) or 15B (northbound) (former exit 18; Frontage Road) in
South Boston, a former
Y interchange where the canceled
Southwest Corridor/
I-95 was to meet with I-93 and run concurrent northward into downtown. The southern terminus is at the Y interchange (the "
Braintree Split") at exit 7 in
Braintree (the former southern terminus of
Route 128). A section of the expressway, beginning south of the Savin Hill overpass and ending just before the Braintree Split, utilizes a
zipper lane, in which a movable barrier carves out a reversible
high-occupancy vehicle lane (HOV lane) on the non-peak side of the highway during
rush hour. Most of the right of way for the
Granite Railway in
Milton and
Quincy was incorporated into the expressway. On August 21, 1969, a train of three runaway locomotives burst out of what is now
Cabot Yard, across Frontage Road, and blocked the northbound side of the highway.
Boston as it travels on the Zakim Bridge (looking south) to the
Southeast Expressway with
Great Blue Hill visible in the background The
Central Artery, officially the John F. Fitzgerald Expressway, was a section of highway in Downtown Boston constructed in the 1950s and was originally designed as a fully
elevated highway. This new highway was greatly disliked by the citizens of the city because it cut the heart of the city in half; cast long, dreary shadows; and was an eyesore to the community. Because of the public outcry, Governor
John A. Volpe ordered the southern half of the highway redesigned so that it was underground; this section became known as the
Dewey Square Tunnel. With the cancelation of the highway projects leading into the city in 1972 by Governor
Francis Sargent, the Central Artery gained the designation of I-93 in 1974. It has also carried the local highway designations of
US 1 (since 1989) and
Route 3. By the mid-1970s, I-93 had outgrown its capacity and had begun to deteriorate due to a lack of maintenance. State Transportation Secretary
Frederick P. Salvucci, aware of the issues surrounding the elevated roadway, proposed a plan conceived in the early 1970s by the
Boston Transportation Planning Review to replace the rusting elevated six-lane Central Artery with a new, more efficient underground roadway. This plan was merged with a long-standing proposal to build a third harbor tunnel to alleviate congestion in the
Sumner and
Callahan tunnels to
East Boston; the new plan became known as the Central Artery/Tunnel Project or the
Big Dig. These new roadways were built during a 12-year period from 1994 to early 2006. The massive project became the largest urban construction project ever undertaken in US history. Construction on the new I-93 segment was not without serious issues: a lengthy federal environmental review pushed the start of construction back from approximately 1990, causing many inflationary increases, while funding for the project was the subject of several political battles between President
Ronald Reagan and Representative
Tip O'Neill. Major construction on the new roadway was done while maintaining the old roadway, a step that also greatly increased the cost of the project. The original
Charles River crossing, named Scheme Z, was the object of great public outcry similar to that of the building of the original highway. The outcry eventually led to the replacement of Scheme Z with a newer, more sleek
cable-stayed bridge and complementing exit for
Cambridge, increasing the cost even more. In Downtown Boston, I-93 is made up of the
O'Neill Tunnel and
Leonard P. Zakim Bunker Hill Memorial Bridge, which spans the Charles River. The underground construction of the tunnel system was completed as of October 2006; however, repairs continue to many parts of the tunnel due to water leakage because of improper construction of the
slurry walls supporting the O'Neill Tunnel. The former route of the above-ground Artery, so named "the other
Green Monster" by Mayor
Thomas Menino, was replaced mostly by open space known formally as the
Rose Fitzgerald Kennedy Greenway. Additional improvements were done in the
South Bay section of the highway: the I-90/I-93 interchange was completely redesigned, a new
HOV lane extending from the zipper lane in Quincy was added and the South Boston Haul road that was constructed to bypass truck traffic around residential streets in the South End was opened to general traffic. Hazardous cargos are prohibited from I-93 in Boston over safety issues in the tunnels; these cargos must exit at either the
Leverett Circle connector when traveling southbound or at the Massachusetts Avenue exit when traveling northbound.
Northern Expressway The Northern Expressway was constructed from
Medford to the New Hampshire border between 1956 and 1963. It was extended through
Somerville and
Charlestown to the
Central Artery,
US 1, and the planned route of the
Inner Belt Expressway (proposed I-695) between 1965 and 1973. Because it was already under construction, the highway was granted an exception to the moratorium on highway expansion inside
Route 128 that was announced in 1970. I-93 was originally planned with a southern terminus in Cambridge (just north of Boston), where it was to meet the Inner Belt (I-695). However, when that route was canceled and the I-95 section into Boston was canceled and rerouted onto
Route 128 in the mid-1970s, I-93 was extended an additional southward down the Central Artery (which had been signed as a concurrency of I-95 and Route 3 before I-95 was rerouted) and the
Southeast Expressway (what was then just Route 3) from Boston to
Braintree and then west along Route 128 (which was later removed from this section of road in 1997) to terminate at I-95 in Canton. In an attempt to alleviate rush-hour traffic jams, travel in the
breakdown lane of I-93 is permitted between exit 35 (formerly 41) and exit 46 (formerly 43), where the highway currently has three lanes in each direction. This extra travel is permitted on the southbound side on weekdays between 6:00 am and 10:00 am and on the northbound side between 3:00 pm and 7:00 pm to align with commuting hours. However, on most busy days, this fails to prevent traffic delays. The
Massachusetts State Police has expressed displeasure with this arrangement, citing that traffic in the breakdown lanes interferes with the ability of emergency vehicles to respond to accidents.
Rapid bridge replacement project In August 2010, in Medford, a section of bridge deck on the northbound side partially collapsed due to age-related structural fatigue. The collapse forced the
Massachusetts Department of Transportation (MassDOT) to evaluate the remaining bridges along the corridor, eventually deciding to replace several bridges along the highway in a plan called 93 Fast 14. MassDOT set in motion a plan to replace the superstructure and concrete decks on 14 overpass bridges along that section of the Interstate, using
rapid bridge replacement methods. The $98.1-million (equivalent to $ in ) project replaced bridges originally built in 1957 with a set of prefabricated modular concrete bridges in a series of weekend roadway closures. Traffic was diverted into a series of crossover lanes during construction. The main part of the project took place each weekend from June through August 2011, with the exception of the
July 4 holiday weekend. One or two bridges were replaced each weekend during the construction time frame. The project was part of the commonwealth's Accelerated Bridge Program.
Methuen Rotary Off exit 43 (formerly 46) in
Methuen, the surface level
traffic circle was rebuilt as part of an overall infrastructure improvement that also included constructing a new bridge carrying the Interstate over the local road, reconstructing on- and offramps to the highway, and realigning the Interstate itself.
New Hampshire As originally envisioned by the federal government, I-93 would have followed the route of present
US 3/
Northwest Expressway/
Everett Turnpike from Boston to
Concord. By 1956, the two states had drawn up new plans for I-93 to the east, bypassing the tolled Everett Turnpike from
Manchester southward along a new alignment, known as the "Northern Expressway" in Massachusetts and crossing into New Hampshire in
Salem. The New Hampshire section south of Hooksett would be named the Alan B. Shepard Highway, named for the
first American in space, a
Derry native. The first part of I-93 completed in New Hampshire opened in Salem from the Massachusetts border to exit 2 (
NH 38/
NH 97) in August 1961. The route was extended gradually northward over the next several years, reaching exit 3 (
NH 111) by the end of 1961, as well as a second segment from the I-293/NH 101 west interchange to exit 7 (NH 101 east) at the same time. The two segments were connected in late 1962. This left a gap in I-93, as traffic was directed along NH 101 West and the Everett Turnpike, while the southern segment of I-93 continued on and ended in a stub at exit 7. replacing US 3. Originally, this road was not included in I-93, as it had its own exit numbers and was signed "TO I-93", though, later, the parkway was officially added to the Interstate System despite the substandard conditions and the exits renumbered. The parkway opened in June 1988, replacing Route 3, and grade crossings were replaced by an overpass. Begun in 2006 and continuing until 2021, the portion between the state border and the I-293 southern terminus was widened to eight lanes; this necessitated the rebuilding and/or relocation of several interchanges. An additional exit has been proposed near milemarker 13 that would include a new connector road to
NH 28, effectively bypassing downtown
Derry and relieving traffic along
NH 102 at exit 4. Construction began in 2023.
Vermont Construction of I-93 in Vermont was completed in 1982. It was planned to be built longer if I-91 did not change its designation eastward in the northeastern part of the state. It was the last Interstate to be built in the state. ==Future expansion==