Big public works projects can lead to big hassles. And one of the largest highway projects in recent memory—Boston's Big Dig, which buried a major interstate below a major city—created more than its fair share. But recent criticisms of the project, saying suburban traffic congestion has essentially made the project a gigantic failure are way off the mark.

The history of the Big Dig began in the post-WWII Interstate Highway boom. Boston, then a decaying industrial and shipping center, was searching for ways from becoming a regional backwater. Aside from bulldozing an entire neighborhood to make way for modern high-rise towers and government offices, the notorious Boston Redevelopment Authority also decided the city needed direct Interstate access to keep downtown commerce vital.

The solution was an elevated, double-decker, three-lane highway called the Central Artery; an ugly, loud, exhaust-spewing eyesore that was congested almost from the day it opened. The highway, and neighborhood-splitting clearances in other parts of Boston proved so unpopular that a second urban highway that might have alleviated some of the congestion by providing a circumferential route around downtown was cancelled due to community protests. This left Boston with only two interstates: East/West Interstate 90 and North/South Interstate 93, with the closest beltway some 10 miles out, along the Route 128 corridor.

While this resulted in some legendary traffic snarls, it also brought—by necessity—some tremendous sustainability improvements to the Boston area. Areas that had been cleared for cancelled freeways were used for a realigned and improved mass transit line and massive park-and-ride lots, allowing low-carbon commutes from Boston's Northern suburbs. In the city itself, the new transit line allowed a dilapidated elevated railway to be demolished, providing faster, more reliable service, and clearing the way for the final leg of Amtrak's Northeast Corridor to be electrified. In Cambridge, Brookline, Jamaica Plain, and other municipalities along the cancelled Inner Belt route, a prominent bicycle-commuting culture arose.

After the Big Dig finally uncorked the infuriating downtown bottleneck, the elevated artery was replaced with the Rose Kennedy Greenway, a linear park through Boston's urban core that has furthered its reputation as the country's most walkable city. Much of the city's car related air pollution left with the congestion, while vast stretches of Boston's historic North End and Waterfront were open to the sky once more, enticing more pedestrians to the regions, and resulting in an economic boom.

Though congestion and commute times along I-93 outside the city have increased, it's hardly the fault of the Big Dig. Historically low gas prices and a complete lack of tolls on the highway gave decades of commuters no economic incentive to avoid the crowded commute. By comparison, toll-heavy I-90 suffers far fewer congestion problems at peak hours, despite reaping similar benefits from the Big Dig's improved traffic flow. Underinvestment in mass transit during the 1990s has also fueled the problem, as late trains and unreliable track conditions pushed more commuters onto the highways.

The Big Dig has had a few undesirable environmental consequences, but most of that burden has been borne by communities just outside of Boston, which now carry the bulk of the circumferential traffic from the newly improved Big Dig on parkways and surface streets, resulting in elevated levels of noise, air pollution and lung cancer. But with an upcoming extension of the urban subway line, many of these environmental problems will be substantially mitigated. If anything, America needs more projects like the Big Dig to secure a sustainable future.