The Leonard P. Zakim Bunker Hill Memorial Bridge in Boston, Massachusetts 42.3694° N 71.06427° W is the widest cable-stayed bridge built prior to 2003. The bridge is part of the Big Dig, the largest overall highway construction project in the United States, and replaced the Charlestown High Bridge.

According to the Massachusetts Turnpike Authority's web site, the bridge has an overall length of 436.5 m, a main span of 227.1 m, side spans of 81.4 m (downtown side) and 128.0 m (Charlestown side), and towers that are 82.3 m tall.

In a cable-stayed bridge, instead of hanging the roadbed from cables slung over towers, the cables run directly between the roadbed and the towers. Although cable-stayed bridges have become common in Europe since World War II, they are relatively new to North America.

The bridge, designed by Swiss civil engineer Christian Menn, follows a new design in which two outer lanes are cantilevered outside the towers while another eight lanes run through the towers. It has a striking, graceful appearance that is meant to echo the towers of the Bunker Hill Monument, which is within view of the bridge, and the white cables of the USS Constitution.

Its name commemorates both the battle and Boston civic leader Leonard P. Zakim, who championed "building bridges between peoples". A local nickname for the bridge is the "Bill Buckner Bridge," due to the fact that the towers look like legs straddling the bridge and "the cars go right through them."

Although the bridge was completed in 2002, the new bridge was not opened to traffic until the northbound Central Artery tunnel opened in early 2003. The cantilevered northbound lanes (a two-lane entrance ramp) opened in April 2005, when the old bridge was sufficiently demolished to allow for their completion. The southbound lanes were opened in December 2003, with the opening of the southbound tunnel.

The bridge carries Interstate 93 and US 1 across the Charles River. The Big Dig tunnel entrance is at its southern end. The Zakim cable-stayed bridge has been widely seen as an improvement, it acts as a complete replacement of the previous two-lane, dual height steel bridge once known by the simple generic moniker as the "upper and lower decks."

In March, 2005 problems arose when it became appearent that ice falling off the cables during the course of winter could land in large enough chunks on the roadway below to possibly endanger motorists, or even break windshields. Some motorists are left feeling compelled to keep one eye on the road ahead, and another eye on the cables above while driving across the bridge.

(Source: Wikipedia)

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