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. Twin bridges are independent structures and each bridge has its own superstructure, substructure, and foundation. [1] 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.
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. [1]
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridges, which lack vertical suspenders, have a long history in many mountainous parts of the world.
Tower Bridge is a Grade I listed combined bascule, suspension, and, until 1960, cantilever bridge in London, built between 1886 and 1894, designed by Horace Jones and engineered by John Wolfe Barry with the help of Henry Marc Brunel. It crosses the River Thames close to the Tower of London and is one of five London bridges owned and maintained by the City Bridge Foundation, a charitable trust founded in 1282.
A cable-stayed bridge has one or more towers, from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly.
The Goethals Bridge is the name of a pair of cable-stayed bridge spans connecting Elizabeth, New Jersey, to Staten Island, New York, in the United States. The spans cross a strait known as Arthur Kill, and replaced a cantilever bridge span built in 1928. The bridge is operated by the Port Authority of New York and New Jersey.
The Lions Gate Bridge, opened in 1938 and officially known as the First Narrows Bridge, is a suspension bridge that crosses the first narrows of Burrard Inlet and connects the City of Vancouver, British Columbia, to the North Shore municipalities of the District of North Vancouver, the City of North Vancouver, and West Vancouver. The term "Lions Gate" refers to the Lions, a pair of mountain peaks north of Vancouver. Northbound traffic on the bridge heads in their general direction. A pair of cast concrete lions, designed by sculptor Charles Marega, were placed on either side of the south approach to the bridge in January 1939.
The Blue Water Bridge is a twin-span international bridge across the St. Clair River that links Port Huron, Michigan, United States, and Point Edward, Ontario, Canada. The Blue Water Bridge connects Highway 402 in Ontario with both Interstate 69 (I-69) and Interstate 94 (I-94) in Michigan.
The Richmond–San Rafael Bridge is the northernmost of the east–west crossings of California's San Francisco Bay, carrying Interstate 580 from Richmond on the east to San Rafael on the west. It opened in 1956, replacing ferry service by the Richmond–San Rafael Ferry Company, and was officially renamed in 1981 to honor California State Senator John F. McCarthy, who championed the bridge's creation.
The Carquinez Bridge is a pair of parallel bridges spanning the Carquinez Strait at the northeastern end of San Francisco Bay. They form the part of Interstate 80 between Crockett and Vallejo, California, United States.
The Silver Jubilee Bridge crosses the River Mersey and the Manchester Ship Canal at Runcorn Gap between Runcorn and Widnes in Halton, England. It is a through arch bridge with a main arch span of 361 yards. It was opened in 1961 as a replacement for the Widnes–Runcorn Transporter Bridge. In 1975–77 the carriageway was widened, after which the bridge was given its official name in honour of the Queen's Silver Jubilee. It carries the A533 road and a cantilevered footway. The bridge is recorded in the National Heritage List for England as a designated Grade II listed building. The bridge was closed to vehicles for refurbishment upon the opening of the new Mersey Gateway Bridge, but reopened as a toll bridge in February 2021.
The Howrah Bridge is a balanced steel bridge over the Hooghly River in West Bengal, India. Commissioned in 1943, the bridge was originally named the New Howrah Bridge, because it replaced a pontoon bridge at the same location linking the twin cities of Howrah and Kolkata, which are located at the opposite banks of each other. On 14 June 1965, it was renamed Rabindra Setu after the Bengali poet Rabindranath Tagore, who was the first Indian and Asian Nobel laureate. It is still popularly known as the Howrah Bridge.
The eastern span replacement of the San Francisco–Oakland Bay Bridge was a construction project to replace a seismically unsound portion of the Bay Bridge with a new self-anchored suspension bridge (SAS) and a pair of viaducts. The bridge is in the U.S. state of California and crosses the San Francisco Bay between Yerba Buena Island and Oakland. The span replacement took place between 2002 and 2013, and is the most expensive public works project in California history, with a final price tag of $6.5 billion, a 2,500% increase from the original estimate of $250 million, which was an initial estimate for a seismic retrofit of the span, not the full span replacement ultimately completed. Originally scheduled to open in 2007, several problems delayed the opening until September 2, 2013. With a width of 258.33 ft (78.74 m), comprising 10 general-purpose lanes, it is the world's widest bridge according to Guinness World Records.
The Interstate 74 Bridge, officially known as the Iowa-Illinois Memorial Bridge, and often called The Twin Bridges, or the I-74 Bridge, are basket-handle, through arch twin bridges that carry Interstate 74 across the Mississippi River and connect Bettendorf, Iowa, and Moline, Illinois. It is located near the geographic center of the Quad Cities. They replace two suspension bridges opened to traffic in 1935 and 1959, both of which had become obsolete by the 1990s.
The Roberto Clemente Bridge, also known as the Sixth Street Bridge, spans the Allegheny River in downtown Pittsburgh, Pennsylvania, United States.
Wandsworth Bridge crosses the River Thames in west London. It carries the A217 road between the area of Battersea, near Wandsworth Town Station, in the London Borough of Wandsworth on the south of the river, and the areas of Sands End and Parsons Green, in the London Borough of Hammersmith and Fulham, on the north side.
The Newark Bay Bridge of the Central Railroad of New Jersey (CNJ) was a railroad bridge in New Jersey that connected Elizabethport and Bayonne at the southern end of Newark Bay. Its third and final incarnation was a four-track vertical-lift design that opened in 1926, replacing a bascule bridge from 1904 which superseded the original swing bridge from 1887. The bridge served the main line of the CNJ, carrying daily interstate trains as well as commuter trains.
The Varodd Bridges are two parallel cantilever bridges in Kristiansand municipality, in Agder county, Norway, and they cross the Topdalsfjorden. They are named after the peninsula on the western shore. It goes from Vige and ends in Søm in Kristiansand. The bridges carry the European route E18 highway over the fjord.
The bridges of Budapest, Hungary, crossing the River Danube from north to south are as follows:
The I-10 Twin Span Bridge, a nearly 5.5-mile (8.9 km) causeway officially known as the Frank Davis "Naturally N'Awlins" Memorial Bridge, consists of two parallel trestle bridges. These parallel bridges cross the eastern end of Lake Pontchartrain in southern Louisiana from New Orleans to Slidell. The current bridge spans were constructed in the second half of the 2000s after the original bridges were extensively damaged by Hurricane Katrina on August 29, 2005. The first span opened to eastbound traffic on July 9, 2009. On April 7, 2010, the second span was opened to traffic and the old twin spans were permanently closed to traffic.
The Senator Roy Blunt Bridge is a twin continuous through arch truss bridge over the Missouri River at Jefferson City, Missouri, which carry U.S. Routes 54 (US 54) and 63 between Cole County and Callaway County. Before being officially named for former Missouri Senator Roy Blunt in 2022, the bridge was known as the Jefferson City Bridge.
The Dongshuimen Bridge and the Qiansimen Bridge, known collectively as the Twin River Bridges, are a pair of bridges that form a road and rail connection in Chongqing, China. Consisting of two cable-stayed bridges and a tunnel across the Yuzhong peninsula where the heart of Chongqing's commercial & financial district Jiefangbei CBD is located, the connection opened in 2014.
In order to ensure better management and maintenance of such structures, but also in order to limit the risk that the bridge must be closed in cases of serious highway accidents, most authorities impose a solution of twin bridges which are totally independent of each other. It is clear that in most common cases this is a reasonable and judicious solution.