List Of Tunnels In Pittsburgh
Tunnels See also * List of bridges of Pittsburgh References {{reflist Tunnels in Pennsylvania Tunnels Pittsburgh Pittsburgh ( ) is a city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County, Pennsylvania, Allegheny County. It is the most populous city in both Allegheny County and Wester ...

List Of Bridges Of Pittsburgh
The Bridges of Pittsburgh play an important role in the city's transportation system. Without bridges, the Pittsburgh region would be a series of fragmented valleys, hillsides, river plains, and isolated communities. A 2006 study determined that, at the time, Pittsburgh had 446 bridges. With its proximity to three major rivers and countless hills and ravines, Pittsburgh is known as ''"The City of Bridges"''. History Pittsburgh's first river bridges, made of wood and long since replaced, opened in 1818 at Smithfield Street and 1819 at Sixth Street (then St. Clair Street). The city's oldest in-service bridge is the current Smithfield Street Bridge, which opened in 1883; it was designated a National Historic Landmark in 1976. Pittsburgh waged a massive road and bridge building campaign from 1924 to 1940; most of Pittsburgh's oldest major bridges date from this period. The coming of the Interstate Highway System triggered more construction in the second half of the twentieth centur ...
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Tunnels In Pennsylvania
A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods. A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usually in the tunnel. Some tunnels are used as sewers or aqueducts to supply water for consumption or for hydroelectric stations. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment. Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people. Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely. Tunne ...
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