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38-580: The Spit Bridge , a steel and concrete girder bridge with a bascule lift span across the Middle Harbour , is located 10 kilometres (6.2 mi) north-east of the central business district in Sydney , Australia. The bridge carries The Spit Road ( A8 ) from a point called The Spit , and connects the suburbs of Mosman , on the south bank and Seaforth , on the north bank. Sydney's Lower North Shore and Northern Beaches were serviced initially by

76-466: A "suicide lane" for their notorious fatality rates, especially in the United States in settings with high traffic speeds (45 mph), and on roads with five or more lanes (typically two or three lanes in each travel direction with one center turn lane). However, some studies have found that converting high-speed four lane streets into three lane streets (one lane of traffic in each direction with

114-415: A beam or girder bridge, the beams themselves are the primary support for the deck, and are responsible for transferring the load down to the foundation. Material type, shape, and weight all affect how much weight a beam can hold. Due to the properties of the second moment of area , the height of a girder is the most significant factor to affect its load capacity. Longer spans, more traffic, or wider spacing of

152-463: A bus lane running against a one-way street through the opposite direction Contraflow Lane Reversal : Typically used to refer to a temporary setup of a lane running opposite to normal during special times, such as emergency evacuations, sports tournaments, or road construction/repairs. Reversible Lane : Typically used to refer to a lane specifically designed to facilitate different directional usage regularly, with changes sometimes as frequent as twice

190-435: A center turn lane) and lowering speed limits can result in improved safety, despite the use of a center turn lane, as traffic collisions occur at far lower speeds. These roads are very common in suburban areas and less common in rural areas, though they are frequent around developed areas near Interstate Highway bypasses in the United States. Many were divided highways before the median was demolished or otherwise replaced by

228-748: A central lane from one side of the road to another; some examples are the five-lane San Diego-Coronado Bay Bridge in San Diego, California , the seven-lane Alex Fraser Bridge on the Fraser River in Vancouver and the eight-lane Auckland Harbour Bridge across the Waitemata Harbour in Auckland , New Zealand. Other systems use retractable cones or bollards which are built into the road, or retractable fences which can divert traffic from

266-440: A configuration are often referred to as "express lanes"). Generally, traffic flows in one direction or another in such a configuration (or not at all); the carriageways are not "split" into two-lane roadways during non-rush periods. Typically, this sort of express lane will have fewer interchanges than the primary lanes, and many such roadways only provide onramps for inbound traffic, and offramps for outbound traffic. Historically,

304-424: A day. There are typically three types of reversible lanes: While reversible lane is a commonly used term, other terms include variable lanes, dynamic lanes, and flex lanes. Some more recent implementations of reversible lanes use a movable barrier to establish a physical separation between allowed and disallowed lanes of travel. In some systems, a concrete barrier is moved during low-traffic periods to switch

342-499: A high-level bridge in place of the existing one. David Barr , the member for Manly , claimed in 2002 that the latter two were too expensive with $ 200 million estimated for a high-level bridge, and $ 1 billion for the tunnel. In 2009 it was reported that the Labor Government was reviewing a proposal for a tunnel from Cammeray to The Spit, linked to a new, higher bridge that would be able to let boats through without

380-474: A parking lot from a street. 2+1 roads have replaced some of these, mainly in Europe. Another type of center two-way lane is a "two-way left turn lane" (TWLT) or "center left-turn lane", or (for countries that drive on the right ) "center turn lane" or "median turn lane", a single lane in the center of the road into which traffic from both directions pulls to make a left turn. This lane is also sometimes called

418-529: A reversible ramp. The two center lanes of the six-lane Golden Gate Bridge are reversible; they are southbound during morning rush hour and northbound at evening rush hour. Prior to the installation of a movable median barrier in January 2015, they were demarcated by vertical yellow markers placed manually in sockets in the roadway. Many urban freeways have entirely separate carriageways (and connecting ramps) to hold reversible lanes (the reversible lanes in such

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456-543: A rowing boat from as early as 1829. A hand-operated punt service began in 1850 and continued until 1889, when it was replaced by a steam punt. The inhabitants of the Manly area first requested a bridge in the 1870s and the first plans for one were made in the following decade. In 1912, Member of Parliament Richard Arthur lobbied the State Government to build a bridge, but was told that the planned construction of

494-529: A width of 44 feet (13 m) and a pedestrian walkway of 5 feet (1.5 m) on either side. There are three spans at either end of the opening span. Each of the six fixed spans have four welded plate girders as the main members, with cross girders, but without stringers or horizontal bracing. The concrete deck is dowelled to the steelwork. The opening span (Span 4) is a single-leaf bascule. It has two main girders, with cross girders and stringers, covered by an open mesh steel deck. The two footways are of concrete on

532-421: Is a managed lane in which traffic may travel in either direction, depending on certain conditions. Typically, it is meant to improve traffic flow during rush hours, by having overhead traffic lights and lighted street signs notifying drivers which lanes are open or closed to driving or turning. Reversible lanes are also commonly found in tunnels and on bridges, and on the surrounding roadways – even where

570-405: Is box-like and supports all machinery for the operation of the bascule, including the operator's cabin. The approaches and abutments at each end are varied due to the nature of the topography. The southern abutment is built up from the sandy beach level and has a retaining wall faced with stone on either side. The northern abutment is resting directly on the rock on the western side and is built up on

608-491: Is everything from the bearing pads, up - it is what supports the loads and is the most visible part of the bridge. The substructure is the foundation which transfers loads from the superstructure to the ground. Both must work together to create a strong, long-lasting bridge. The superstructure consists of several parts: The substructure is made of multiple parts as well: Reversible lane A reversible lane , also known as variable lane , dynamic lane , and tidal flow ,

646-408: Is no longer a true girder bridge. Girder bridges have existed for millennia in a variety of forms depending on resources available. The oldest types of bridges are the beam , arch and swing bridges, and they are still built today. These types of bridges have been built by human beings since ancient times, with the initial design being much simpler than what we utilize today. As technology advanced

684-412: Is often used interchangeably with "beam" in reference to bridge design. However, some authors define beam bridges slightly differently from girder bridges. A girder may be made of concrete or steel. Many shorter bridges, especially in rural areas where they may be exposed to water overtopping and corrosion, utilize concrete box girder. The term "girder" is typically used to refer to a steel beam. In

722-891: The Beaches Link project. The tunnel, which is expected to take five years to build, will connect the Warringah Freeway from Cammeray and cross underneath Middle Harbour to meet up with the Burnt Bridge Creek deviation at Balgowlah . The proposed tunnel will be located west of The Spit Bridge. However, in June 2022, the NSW Government announced that the Beaches Link section of the project would be shelved indefinitely, due to market constraints and labour shortages. Girder bridge The term "girder"

760-616: The Minister for Roads Eric Roozendaal and the five–year plan was abandoned. Traffic delays either side of The Spit Bridge have been a problem for many years, not only on the approaches to the bridge itself, but also far up the hills on either side. Proposals to ameliorate delays have included widening the bridge, a tunnel linking the Warringah Expressway and the Burnt Bridge Creek Deviation , and

798-575: The Sydney Harbour Bridge made this unlikely. World War I pushed the issue aside but more calls for a bridge were made in 1919. In 1922, the cost of a bridge was estimated at £150,000 by the Public Works Committee, a price that Manly Council said would cover a 205-metre-long concrete bridge, resting on 18 arches of varying lengths, with two sets of tram lines, two roadways and two footpaths. Eventually, in late 1923,

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836-478: The Council decided to build a bridge itself on a cost of £40,000 to £60,000 with a low height design made from timber that was 213m long, with a roadway 5.5m wide and room for one covered footpath, but no tram lines. In 1924, The (first) Spit Bridge was completed and opened. By 1927 the timber low–level bridge saw a 60% growth over that of the punt for the year prior to the bridge opening. The amount of traffic using

874-473: The approaches to it have three lanes in each direction. In 2007, the Roads & Traffic Authority found that traffic either side of the bridge doesn't return to normal for 15 minutes after the bridge is opened and reduced the number of bridge opening times. Grade-separated shared pedestrian footpaths and cycleways are located on the bridge's western (upriver) and eastern (downriver) sides. The Spit Bridge

912-404: The beams will all directly result in a deeper beam. In truss and arch -style bridges, the girders are still the main support for the deck, but the load is transferred through the truss or arch to the foundation. These designs allow bridges to span larger distances without requiring the depth of the beam to increase beyond what is practical. However, with the inclusion of a truss or arch the bridge

950-538: The bridge to six lanes, with two extra traffic lanes and a pedestrian/cycleway being added on the western side, and upgrades to the lifting mechanism. Construction was to have begun in 2007, however, the project was scrapped in May of that year. According to the government this was due to technical and engineering difficulties, according to the opposition it was because of political considerations. The increased cost estimates to $ 115 million were deemed to be not justifiable by

988-401: The bridge was higher than expected and the subsequent revenue from tolls providing a financial boon for the government. Various plans were considered to reduce congestion including a high-level bridge and a bridge further upstream, leaving the existing bridge for local traffic; however none were enacted until after World War II . The NSW Government decided to build another low–level bridge at

1026-993: The center lane of such a highway for passing slow-moving vehicles, except when funding or space constraints dictate use of it as a rush hour "travel lane" when traffic is largely asymmetric between a central business district and its suburbs. U.S. Route 13 near the Greenville, North Carolina , city limits is a rare instance of a posted warning sign that states "do not pass in center lane". British Columbia Nova Scotia Ontario Alberta Quebec Alabama Alaska Arizona California District of Columbia Florida Georgia Indiana Kentucky Maryland Michigan Nebraska New Jersey New York North Carolina Ohio Pennsylvania South Carolina Tennessee Texas Utah Virginia In shopping centres and metro stations there may be an odd number of escalators, with one or more escalators running in different directions in different time of

1064-413: The eastern side with a retaining wall. Due to the variation in ground level on each shore there is a grade of 2.68% from south to north. Traffic across the bridge is regulated by traffic lights at either end (located at the end of Spans 2 and 6) and by roadway gates which operate as the bridge is about to open. The bridge has two traffic lanes in each direction, with a tidal flow system established, while

1102-511: The fixed spans, and steel on the bascule span. The piers either side of the opening span are flanked by fenders , and when the bridge is in the open position a navigation channel of 80 feet (24 m) wide is created. At the Mosman end the slab and two column piers rest on concrete piles driven into the sands of the harbour bed at a depth of between 40 and 50 feet (12 and 15 m). At the Manly end

1140-422: The harbour bottom slopes up steeply to outcropping rock on which the northern abutment sits. Piers 5 and 6 are double cylinder piers sitting on bedrock below the harbour bed. The main pier which supports the bascule span is Pier 4. It rests on four cylinders taken down to sandstone bedrock at a depth of between 45 and 75 feet (14 and 23 m) which is 75 and 105 feet (23 and 32 m) below mean sea level. The pier

1178-459: The lanes are not regularly reversed to handle normal changes in traffic flow. The presence of lane controls allows authorities to close or reverse lanes when unusual circumstances (such as construction or a traffic mishap) require use of fewer or more lanes to maintain orderly flow of traffic. There are similar setups with slightly different usages, although the terms may be commonly used interchangeably. Contraflow Lane : Typically used to refer to

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1216-401: The methods were improved and were based on the utilization and manipulation of rock, stone, mortar and other materials that would serve to be stronger and longer. In ancient Rome , the techniques for building bridges included the driving of wooden poles to serve as the bridge columns and then filling the column space with various construction materials. The bridges constructed by Romans were at

1254-439: The need to be opened. In 2014, Premier Mike Baird , also the member for Manly, announced plans to bypass Mosman and The Spit Bridge by constructing a $ 2–3 billion tunnel from Seaforth to Neutral Bay that would run underground beneath Military Road. In 2017, NSW Premier Gladys Berejiklian announced that the NSW Government will provide $ 77 million towards the construction of a tunnel to bypass The Spit Bridge as part of

1292-440: The same site. Construction of the current bridge by Cleveland Bridge & Engineering Company had commenced in 1952 and after delays was completed in 1958; and opened on 19 November 1958. The Spit Bridge over Middle Harbour can be described as a steel and concrete girder bridge with a bascule lift span. The Spit Bridge comprises 7 spans of a total length of 745 feet 6 inches (227.23 m), has four traffic lanes with

1330-591: The term "suicide lane" has also referred to a lane in the center of a highway meant for passing in both directions. Neither direction has the right-of-way , and both directions are permitted to use the lane for passing. In a similar layout, three lanes are striped with two in one direction and one in the other, but traffic in the direction with one lane is allowed to cross the centerline to pass. Passing lanes should not be confused with turning lanes. While they look similar, passing lanes are for highway overtaking, while turning lanes typically are used to stop and turn into

1368-496: The time basic but very dependable and strong while serving a very important purpose in social life. As the Industrial Revolution came and went, new materials with improved physical properties were utilized; and wrought iron was replaced with steel due to steel's greater strength and larger application potential. All bridges consist of two main parts: the substructure, and the superstructure. The superstructure

1406-548: The turn lane. Many four-lane streets with a center double yellow line are being phased out in favor of 3- or five-lane streets with center turn lanes because the center lane allows for less disruption of traffic flow. For routes with moderate traffic, other movements involve downgrading four-lane undivided streets to three-lane streets with a turn-only center lane. This center lane can be used by emergency vehicles like police cars, ambulance, and fire trucks to avoid traffic traveling in either direction. Drivers are not allowed to use

1444-683: Was listed on the Roads & Traffic Authority heritage and conservation register on 24 November 2003: The Spit Bridge forms part of the route from the Sydney central business district and Lower North Shore suburbs to Manly and the Northern Beaches. The next crossing of Middle Harbour is some distance upstream (north-west) at Roseville Bridge . The Roads & Traffic Authority announced in August 2006 that tenders had been called for widening of

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