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History of The Central Artery / Tunnel Project

To tell the story of the Central Artery/Tunnel Project, or the "Big Dig," it is necessary to go back to the road it replaced, the elevated John F. Fitzgerald Expressway - more commonly known as the Central Artery.

Back in the 1940s - at the same time transportation officials were starting to envision the Massachusetts Turnpike - urban planners saw an increasingly tired-looking city of Boston choking on automobile traffic.

The state Department of Public Works - the agency headed by the same man who would become the first chairman of the Massachusetts Turnpike Authority, William F. Callahan - had the novel idea of building a futuristic 1.5 mile "Highway in the Sky" through downtown Boston, with enough on- and off-ramps to service local destinations.

The elevated highway through downtown Boston

Construction of the Dewey Square Tunnel

The road was intended to work in concert with another highway, called the Inner Belt, that was to circle downtown Boston from the South End and Back Bay across the Charles River to Cambridge and Charlestown. Local traffic would use the elevated Central Artery, while through traffic would use the Inner Belt.

Construction on the Central Artery began in 1950, but the roadway was not without controversy. As late as 1954, the path of the final piece of construction was undecided, until the DPW decided to sink the remainder of the highway into a tunnel from Congress Street to Kneeland Street. This came to be known as the Dewey Square or South Station Tunnel.

And even as it was being built from the Mystic Bridge south, the new artery, which displaced more than 20,000 people and demolished more than 1,000 structures, was seen as ugly and divisive of city neighborhoods. Its construction spurred citizen groups and others to successfully oppose the building of the Inner Belt.

The elevated highway progressed through downtown Boston from north to south. Planners decided to put the southern portion from the Fort Hill neighborhood past Congress Street and Dewey Square to Kneeland Street in a tunnel, because they realized that the elevated portion of the highway was too obtrusive and disruptive in the midst of downtown life.

Central Artery construction concluded in 1959 with the opening of the Dewey Square Tunnel and the Southeast Expressway to Braintree. This new highway, part of Interstate 93, was designed for 75,000 vehicles per day. But from the outset, its 27 on- and off-ramps between Kneeland Street and Causeway Street, combined with a lack of merge and breakdown lanes, made for less than smooth traffic flow. Stall and crawl commuting was born.

Cut-and-cover construction of the Dewey Square Tunnel near South Station, circa 1956.

As early as the late 1960s, transportation planners began considering the next round of congestion-relieving highway construction, but it was not until the late 1980s when federal funding for a new, underground Central Artery and a new Boston Harbor tunnel connecting to Logan Airport was secured.

The entire elevated Central Artery, including the Southeast Expressway to Braintree, opened in 1959, comfortably carrying about 75,000 vehicles a day (above).

Before it was demolished, the elevated Central Artery carried more than 190,000 vehicles a day with a bumper-to-bumper, stop-and-go traffic jam up to eight hours a day. The only place to build a new highway was directly underneath.

By the time Big Dig construction was getting into high gear in the mid-1990s, traffic on the elevated artery was a mind-bending 190,000 vehicles per day, with an accident rate four times the national average for urban interstates. Traffic was bumper-to-bumper for six to eight hours per day, with projections of traffic jams doubling by 2010. Plus, the elevated structure itself was decaying.

After more than a decade of heavy construction, the Big Dig began paying dividends in 2003, with the completion of the I-90 connector to Logan International Airport in January. That new connection to the Ted Williams Tunnel meant the Massachusetts Turnpike had reached its final, 138-mile length. And within months, the new I-93 underground artery and the Leonard P. Zakim Bunker Hill Bridge also opened to traffic.

The new Central Artery has the capacity to carry 250,000 vehicles per day. With the demolition of the old elevated highway, local traffic will travel along newly reconfigured surface streets, which will further facilitate traffic flow since far fewer vehicles will be using the underground artery for intra-city trips.

Meanwhile, the Ted Williams Tunnel allows westbound traffic from the Massachusetts Turnpike to go directly to Logan Airport and the North Shore without having to use I-93. By carrying an estimated 90,000 vehicles per day, the Ted Williams Tunnel reduces the amount of traffic using the Sumner and Callahan Tunnels.

The Williams Tunnel interchange in South Boston is at the center of a vital new development area for Boston, the seaport, with a new convention center and related projects.

In addition to the new street and sidewalk grid being built in downtown Boston, a string of new parks and open spaces will be constructed on the land that used to be in the shadows of a highway above.