The complexity of modern life

The Manhattan Bridge is a suspension bridge that crosses the East River in New York City, connecting Lower Manhattan (at Canal Street) with Brooklyn (at Flatbush Avenue Extension). It was the last of the three suspension bridges built across the lower East River, following the Brooklyn and the Williamsburg bridges. The bridge was opened to traffic on December 31, 1909 and was designed by Leon Moisseiff, who later designed the infamous original Tacoma Narrows Bridge that opened and collapsed in 1940. It has four vehicle lanes on the upper level (split between two roadways). The lower level has three lanes, four subway tracks, a walkway and a bikeway. The upper level, originally used for streetcars, has two lanes in each direction, and the lower level is one-way and has three lanes in peak direction. It once carried New York State Route 27 and later was planned to carry Interstate 478. No tolls are charged for motor vehicles to use the Manhattan Bridge.

The original pedestrian walkway on the south side of the bridge was reopened after forty years in June 2001. It was also used by bicycles until late summer 2004, when a dedicated bicycle path was opened on the north side of the bridge, again in 2007 while the bike lane was used for truck access during repairs to the lower motor roadway, and for a third time in 2011, when ongoing construction on the north side of the bridge necessitated narrow shelters, narrowing the path to make it unsafe for cycling.

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and entertainment. The home of the United Nations Headquarters, New York is an important center for international affairs and is widely deemed the cultural capital of the world. The city is also referred to as New York City or the City of New York to distinguish it from the state of New York, of which it is a part.

Located on one of the world's largest natural harbors, New York City consists of five boroughs which were consolidated in 1898: The Bronx, Brooklyn, Manhattan, Queens, and Staten Island. With a 2010 United States Census population of 8,175,133 distributed over a land area of just 305 square miles (790 km²), New York is the most densely populated major city in the United States. As many as 800 languages are spoken in New York, making it the most linguistically diverse city in the world. The New York City Metropolitan Area's population is the United States' largest, estimated at 18.9 million people distributed over 6,720 square miles (17,400 km²), and is also part of the most populous combined statistical area in the United States, containing 22.2 million people as of 2009 Census estimates. New York has the largest internet presence of any location in the world; registering 7.1 billion search results as of December 2011.

A suspension bridge is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century. Bridges without vertical suspenders have a long history in many mountainous parts of the world.

This type of bridge has cables suspended between towers, plus vertical suspender cables that carry the weight of the deck below, upon which traffic crosses. This arrangement allows the deck to be level or to arc upward for additional clearance. Like other suspension bridge types, this type often is constructed without falsework.

The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. The main cables continue beyond the pillars to deck-level supports, and further continue to connections with anchors in the ground. The roadway is supported by vertical suspender cables or rods, called hangers. In some circumstances the towers may sit on a bluff or canyon edge where the road may proceed directly to the main span, otherwise the bridge will usually have two smaller spans, running between either pair of pillars and the highway, which may be supported by suspender cables or may use a truss bridge to make this connection. In the latter case there will be very little arc in the outboard main cables.