The Big Dig was the most expensive highway project in the United States

The Big Dig, the most expensive highway project in the United States, rearranged Boston's cityscape. This included setting the O'Neill Tunnel beneath the Central Artery, building the Ted Williams Tunnel, and erecting the Zakim Bunker Hill Bridge over the Charles River. These ventures signified a turning point in Boston's urban planning, a reaction to the Massachusetts Department of Public Works' abandoned expressway system. The Central Artery was initially meant to be Interstate 95's downtown Boston stretch, but local businesses, leaders, and residents despised the elevated road for its negative impact.

By the 1990s, the road section was navigated by 190,000 vehicles daily, a sharp increase from the 75,000 in the 1950s. The expressway had tight turns, a multitude of entry and exit points, and entry ramps missing merge lanes. The Big Dig officially kicked off in 1982 with planning and environmental impact studies, construction commencing in 1991. However, the project encountered substantial delays and a towering price tag in its later stages. The project was completed in December 2007 at $14.6 billion - astronomically higher than the original prediction of $2.8 billion.

The Big Dig was finally completed in December 2007. The consortium behind the project - Bechtel and Parsons Brinckerhoff - were not the lone culprits for the fatal flaws, accidents, and other calamities. Numerous smaller companies also agreed to pay a combined sum of approximately $51 million in restitution for the project.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons