With a population of some 2.8 million people, Boston Massachusetts has long been the center of New England’s educational institutions, the Performing Arts, and professional sports. However, along with that distinction Boston was also known for its world-class traffic congestion. The Central Artery Tunnel Project, more commonly known as the “Big Dig”, was Boston’s’ solution to the growing traffic problem.
An Antiquated Interstate
This was particularly the case for the estimated 200,000 vehicles a year that clogged a short 1.5 mile, six-lane section of I-93 located in the heart of downtown Boston. Interstate-93 was a 40-year old steel and concrete elevated highway and the principal conduit that funneled traffic from the northern part of the state, across the Charles River, and into the city. Called the Central Artery, the day-long congestion was exacerbated not only by the sheer volume of vehicles but also by the design of the highway which included numerous entrances and exits, merging lanes that continuously commingled traffic, and tight turns. As a result, the accident rate was reported to be four times the national average for urban interstates. The same problem existed for motorist trying to get to Logan International Airport through the Callahan and Sumner tunnels under Boston Harbor. In fact, conditions were so bad that if present conditions continued, traffic jams of 16 hours were predicted for 2010.
The "Big Dig"
To avoid the prospects of this enormous gridlock and the dire repercussions that were sure to follow, environmental impact studies were conducted on an enormous highway construction project first conceived in the 1970s. Once federal funding for this incredible engineering feat was secured, in 1991 ground was officially broken for the massive project known today as “The Big Dig”.
Tunnel Objectives
Northbound Tunnel
The first task was to replace the 1.5 mile section of the elevated highway coming into downtown Boston from the north with a new eight to ten-lane expressway that now moves the vehicle traffic under the city through a 3.5 mile tunnel. This phase of the project was completed in 2003 and incredibly, while the new tunnel was being built directly beneath the existing elevated section, the construction was accomplished without seriously restricting the traffic flow still flowing into Boston. In addition, five major interchanges were constructed to direct traffic at Logan Airport and in various other locations in the North and Southern areas of Boston.
