Built of steel in cantilevered construction, "The Tap" was built during the Korean War. With steel being needed for the military, the designers and builders were forced to skimp on the bridge, constructing it with virtually no redundancies. Thus, to this day, the loss of a critical structural member would most likely lead to the catastrophic loss of the bridge.
The Tappan Zee Bridge, one of the busiest in the nation, is also one of the most rickety. "[T]he deteriorating concrete . . . falls off the bridge in chunks, sometimes creating holes in the roadway through which the river below can be seen. Forty-five such “punch-throughs” were recorded in the eighteen months prior to a 2009 engineering assessment of the bridge," (New York Magazine, 2013).
A structural engineer brought in to evaluate it has called the bridge the "Scary of Scaries," and it has been called the "Hold Your Breath Bridge." When built, the Tap was estimated to have a usable lifespan of 50 years, which it has now exceeded.
When completed in 1955, the Tap linked rural Rockland County with New York City and its northern suburbs. It is part of the New York State Thruway System, Interstate 87, and Interstate 287.
Since the Tappan Zee Bridge made access to upstate New York far easier, the northern suburbs expanded into Rockland County, and within a few years the bridge was carrying far more traffic than it was designed to hold. Accidents and traffic jams are common on the bridge, which has no shoulders. The bridge now carries 150,000 vehicles per day.
A toll bridge, the Tappan Zee was built just beyond the jurisdiction of the Port of New York And New Jersey Authority, so that monies collected from the bridge go to New York State and not to the Port Authority.
In 2013, New York State commissioned the construction of a new bridge to replace the Tap. The new Tap is expected to open in 2015.