Twin bridges

Twin bridges are a set of two bridges running parallel to each other. A pair of twin bridges is often referred to collectively as a twin-span or dual-span bridge. Bridges of this type are often created by building a new bridge parallel to an existing one in order to increase the traffic capacity of the crossing. While most twin-span bridges consist of two identical bridges, this is not always the case.

The two bridges that form the Chesapeake Bay Bridge, for example, have several differences, most notably in the number of lanes each carries. The longest twin-span bridge is the Lake Pontchartrain Causeway in Louisiana. The Donald and Morris Goodkind Bridges were built at different times.

For a bridge owner, twin bridges can improve the maintenance and management of the structures. For motorists, twin bridges can limit the risk that both directions of traffic will be disrupted by an accident.

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Wikipedia