San Francisco – Oakland Bay Bridge in Oakland

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The San Francisco – Oakland Bay Bridge (known locally as the Bay Bridge) is a pair of bridges spanning San Francisco Bay of California, in the United States. Forming part of Interstate 80 and of the direct road route between San Francisco and Oakland, it carries approximately 270,000 vehicles per day on its two decks. It has one of the longest spans in the world.

The toll bridge was conceived as early as the gold rush days, but construction did not begin until 1933. Designed by Charles H. Purcell, and built by American Bridge Company, it opened for traffic on November 12, 1936, six months before the Golden Gate Bridge. It originally carried automobile traffic on its upper deck, and trucks and trains on the lower, but after the closure of the Key System, the lower deck was converted to road traffic as well.

The bridge was closed on October 27, 2009 due to failure of part of the recently-repaired eastern span. It reopened on November 2.

Composition

The bridge consists of two major crossings connecting each shore with Yerba Buena Island, a natural outcropping located mid-bay. The Western crossing lies between Yerba Buena and San Francisco. It is composed of two complete suspension spans connected at a center anchorage. The top of the Rincon Hill neighborhood serves as the western anchorage and touch-down for the San Francisco landing of the bridge connected by three shorter truss spans. The eastern crossing, between Yerba Buena Island and Oakland, is a cantilever bridge that consists of a double-tower span, five medium truss spans, and a 14-section truss causeway. Due to earthquake concerns the eastern crossing is being replaced by an entirely new crossing, to be finished in late 2013. On Yerba Buena Island, the double-decked crossing consists of a 321 foot concrete viaduct east of the west span's cable anchorage, a 540 foot tunnel through the island's rocky central hill, another 790.8 foot concrete viaduct, and a longer curved high-level steel truss viaduct that spans the final 1169.7 ft to the cantilever bridge. The viaduct sections east of the tunnel are at present being modified, bypassed and replaced as part of the seismic safety work that will eventually transition traffic onto and off of the self-anchored suspension (SAS) bridge of the new eastern bay crossing.

The toll plaza on the Oakland side (since 1969 for westbound traffic only) has eighteen toll lanes, of which six are dedicated FasTrak lanes. Mainline metering signals are located approximately 600 ft west of the toll plaza. Two full-time bus-only lanes bypass the toll booths and metering lights around the right (north) side of the toll plaza; other high occupancy vehicles are permitted to use these lanes during weekday morning and afternoon commute periods. The two far-left toll lanes are operated as high-occupancy vehicle lanes during weekday morning and afternoon commute periods. During the morning commute hours, traffic congestion on the Oakland approach stretches back onto the three feeder highways, Interstate 580, Interstate 880, and Interstate 80 toward Richmond, California. Since the number of lanes on the San Francisco approach is structurally restricted, backups are frequent in the eastbound direction during evening commute hours. The bridge is currently restricted to motorized freeway traffic. Pedestrians, bicycles, and other non-freeway vehicles and devices are not allowed. A California Department of Transportation (Caltrans) bicycle shuttle operates during peak commute hours for $1.00 each way.

Freeway ramps next to the tunnel provide access to Yerba Buena Island and Treasure Island. Because the toll plaza is on the Oakland side, traffic between the island and San Francisco can freely cross back and forth without ever paying a toll. Those who only travel from Oakland to Yerba Buena Island, and not the entire length to San Francisco, must still pay the full toll.

History

Pre-construction

San Francisco, located at the mouth of the bay, was in a perfect location to prosper during the California Gold Rush. Almost all goods not produced locally arrived by ship. But after the first transcontinental railroad was completed in May 1869, San Francisco found itself to be on the wrong side of the bay, separated from the new rail link. The fear of many San Franciscans was that the city would lose its position as the regional center of trade. The concept of a bridge spanning the San Francisco Bay had been considered since the Gold Rush days. Several newspaper articles during the early 1870s discussed the idea. In early 1872, a "Bay Bridge Committee" was hard at work on plans to construct a railroad bridge. The April 1872 issue of the San Francisco Real Estate Circular contained an item about the committee:

The self-proclaimed Emperor Norton I saw fit to decree several times that a suspension bridge be constructed to connect Oakland with San Francisco. Later in 1872, frustrated that nothing had happened, Norton decreed:


Unlike most of Emperor Norton's eccentric ideas, his decree to build a bridge had wide public and political appeal. Yet, the task was too much of an engineering and economic challenge since the bay was too wide and too deep there. In 1921, over forty years after Norton's death, a tunnel was considered, but it became clear that one would be inadequate for vehicular traffic. So the approval of the U.S. Congress, which regulates the armed services and supervises all naval and military bases, was necessary for this island to be used. After a great deal of lobbying, California received Congressional approval to use the island on February 20, 1931.

Construction

The chief engineer was Ralph Modjeski. Construction began on July 9, 1933. The western span of the bridge between San Francisco and Yerba Buena Island presented an enormous engineering situation. The bay was up to 100 ft deep in places and the soil required new foundation-laying techniques. The San Francisco Chronicle report of November 13, 1936, read:

"the greatest traffic jam in the history of S.F., a dozen old-fashioned New Year's eves thrown into one — the biggest and most good-natured crowd of tens of thousands ever to try and walk the streets and guide their autos on them — This was the city last night, the night of the bridge opening with every auto owner in the bay region, seemingly, trying to crowd his machine onto the great bridge.
And those who tried to view the brilliantly lighted structure from the hilltops and also view the fireworks display were numbered also in the thousands.
Every intersection in the city, particularly those near the San Francisco entrance to the bridge, was jammed with a slowly moving auto caravan.
Every available policeman in the department was called to duty to aid in regulating the city's greatest parade of autos.
One of the greatest traffic congestions of the evening was at Fifth and Mission Streets, with downtown traffic and bridge-bound traffic snarled in an almost hopeless mass. To add to the confusion, traffic signals jammed and did not synchronize.
Police reported that there was no lessening of the traffic over the bridge, all lanes being crowded with Oakland- or San-Francisco-bound machines far into the night."

The total cost of construction for the bridge was $77 million. Because it was in effect two bridges strung together, the western spans were ranked the second and third largest suspension bridges. Only the George Washington Bridge had a longer span between towers.

Roadway plan

The original western approach to (and exit from) the upper deck of the bridge was a long ramp to Fifth, branching to Harrison St for westward traffic off the bridge and Bryant St for eastward traffic entering. There was also an on-ramp to the upper deck on Rincon Hill from Fremont Street (that later became an off-ramp) and an off-ramp to First Street (later extended over First St to Fremont St). The lower deck ended at Essex and Harrison St; just southwest of there, the tracks of the bridge railway left the lower deck and curved northward into the elevated loop through the Transbay Terminal that was paved for buses after rail service ended.

There were three original eastern approaches: a viaduct from the end of Cypress Street (State Route 17) in Oakland; a viaduct from the end of 38th Street (U.S. Route 50) at San Pablo Avenue in Oakland; and the Eastshore Highway which carried U.S. Route 40 along the shoreline of Albany, Berkeley and Emeryville.

Until the 1960s the upper deck (58 ft wide between curbs) carried three lanes of traffic in each direction and was restricted to automobiles only. This work was done while the Bay Bridge was in use by using a movable temporary span over the portion being lowered. On the lower deck of the tunnel and its eastern viaduct extension, it was necessary to remove central supports, with each transverse beam (of reinforced concrete) being doubled to take the load across all lanes. It was also necessary to further reinforce each beam supporting the upper deck throughout the entire span, modifications still visible to the traveler.

On February 11, 1968, a U.S. Navy T-33 Shooting Star training aircraft, flying out of the nearby Naval Air Station Alameda, crashed into the eastern span of the bridge, killing both officers. One of the truss sections of the bridges was replaced due to damage from the impact.

The series of lights adorning the suspension cables was added in 1986 as part of the bridge's 50th-anniversary celebration.

On October 27, 2009, during the evening commute, the steel crossbeam and two steel tie rods repaired over Labor Day weekend snapped off the Bay Bridge's eastern span and fell to the upper deck. The cause may have been due to metal-on-metal vibration from bridge traffic and wind gusts of up to 55 mph causing failure of one rod which broke off, which then led to the metal section crashing down. Three vehicles were either struck by or hit the fallen debris, though there were no injuries. On November 1, Caltrans announced that the bridge would probably stay closed at least through the morning commute of Monday, November 2, after repairs performed during the weekend failed a stress test on Sunday. BART and the Golden Gate Ferry systems added supplemental service to accommodate the increased passenger load during the bridge closure. The bridge reopened to traffic on November 2, 2009.

The pieces which broke off on October 27 were a saddle, crossbars, and two tension rods. On March 2, 2004, voters approved Regional Measure 2, raising the toll by another dollar to a total of $3. An additional dollar was added to the toll starting January 1, 2007, to cover cost overruns concerning the replacement of the eastern span.

The Metropolitan Transportation Commission, a regional transportation agency, in its capacity as the Bay Area Toll Authority, administers RM1 and RM2 funds, a significant portion of which are allocated to public transit capital improvements and operating subsidies in the transportation corridors served by the bridges. Caltrans administers the "second dollar" seismic surcharge, and receives some of the MTC-administered funds to perform other maintenance work on the bridges. The Bay Area Toll Authority is made up of appointed officials put in place by various city and county governments, and is not subject to direct voter oversight.

Due to further funding shortages for seismic retrofit projects, the Bay Area Toll Authority again raised tolls on all Bay Area bridges (excluding the Golden Gate Bridge) in July 2010. The toll rate for autos on other Bay Area bridges was increased to $5, but in the Bay Bridge a variable pricing tolling scheme based on congestion was implemented. The Bay Bridge congestion pricing scheme charges a toll from 5 a.m. to 10 a.m. and 3 p.m. to 7 p.m., Monday through Friday. During weekends cars pay . Carpools before the implementation were exempted but now they pay , and the carpool toll discount is now also available only to drivers with FasTrak electronic toll devices. The toll remained at the previous toll of at all other times on weekdays. The Bay Area Toll Authority reported that by October 2010 fewer users are driving during the peak hours and more vehicles are crossing the Bay Bridge before and after the 5-10 a.m. period in which the congestion toll goes into effect. Commute delays in the first six months dropped by an average of 15% compared with 2009.

Popular culture

The bridge has appeared in many movies, including Shadow of the Thin Man, The Graduate, Koyaanisqatsi, George of the Jungle, 2012, Basic Instinct, The Towering Inferno, and The Dead Pool. The bridge has appeared in the video games Resistance 2,", Midtown Madness 2, and Rig'n'Roll. It has also appeared in such science fiction novels as William Gibson's futuristic Bridge trilogy and Cory Doctorow's novel Little Brother, as well as the graphic novel How Loathsome. The new eastern span will appear in the Golden State Warriors logo beginning in the 2011 season.

See also

  • 49-Mile Scenic Drive
  • 2007 San Francisco Bay oil spill
  • Bay Bridge Troll
  • Treasure Island development
  • Eastern span replacement of the San Francisco – Oakland Bay Bridge

Notes

External links

Note: The Transbay Tube crosses the San Francisco – Oakland Bay Bridge, so it is both north and south of the San Francisco – Oakland Bay Bridge.



Source en.wikipedia.org/wiki/San_Francisco_–_Oakland_Bay_Bridge