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A transporter bridge is a type of bridge with a movable platform suspended over a body of water that carries people or cars from one side to the other. It is designed to allow ships to pass through while the platform is out of the way. Despite its practical uses, few of its kind remain today.
Also called a ferry bridge or an aerial transfer bridge, the transporter bridge uses a large portable roadway pulled by thick cables to transfer people and a limited number of vehicles. To ensure no accidents occur, it requires constant human attention because of its interaction with ships. Its times of operation also depend on the weather and water conditions.
A transporter bridge is a type of movable bridge. Its origins stem all the way back to the drawbridges of medieval Europe, where they served as a defense mechanism for towns and castles. A counterweight and winch were used to lift the wooden platform up and down, allowing allies in and keeping foes out.
The ferry bridge first came into use in the late 19th century. During World War II, the first French ferry bridge over the river Seine was destroyed to stop the advancement of German soldiers. Only two such were built in the United States, one in Minnesota and one in Chicago. The Vizcaya Bridge in Spain, which was the first ever transporter bridge, was declared a World Heritage Sight by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 2006.
The Runcorn-Widnes Bridge, one of the first movable bridges in England, could cross the river Mersey in two and a half minutes. It was a major innovation at the time, and over the centuries, it required numerous improvements to keep it operational. It was carrying over two million passengers and a quarter of a million vehicles per year in 1958. The bad weather caused many closings, because the portable car did not have the capacity to dock. It survived until 1961, when it was demolished—for a greater sum than it cost to build it—to make way for a new road bridge.
With the rapid rise of automobiles in the 20th century, transporter bridges were largely deemed obsolete. Most cannot handle the volume of traffic, and their high maintenance makes them impractical for most cities. These bridges were replaced by more convenient ones, and taken out of production. The United Kingdom has the most surviving exemplars today with four, though only three are still in use.