Question: Interstate 80 crosses San Francisco at an edifice that carries how many vehicles?
Context: Six Minute Ferry operated an automobile ferry service across Carquinez Strait on the main highway between Sacramento and Oakland, California.  Each crossing near the present Interstate 80 bridge took approximately 6 minutes.  As automobile travel became increasingly popular, the company ordered some new steel ferries in 1921.  The ferry company went out of business while the ferries were under construction after a March 1922 landslide destroyed the Six Minute Ferry north shore terminal on Morrow Cove.  Southern Pacific Transportation Company purchased the ferries ordered by Six Minute Ferry and placed them in service between San Francisco and Oakland.  The three ferries remained in service on various San Francisco Bay routes until completion of the San Francisco–Oakland Bay Bridge in 1936 and the Golden Gate Bridge in 1937. Interstate 680 (I-680) is a north–south Interstate Highway in Northern California.  It curves around the eastern cities of the San Francisco Bay Area from San Jose to Interstate 80 at Fairfield, bypassing cities along the eastern shore of San Francisco Bay such as Oakland and Richmond while serving others more inland such as Pleasanton and Concord. The San Francisco–Oakland Bay Bridge (known locally as the Bay Bridge) is a complex of bridges spanning San Francisco Bay in California.  As part of Interstate 80 and the direct road between San Francisco and Oakland, it carries about 260,000 vehicles a day on its two decks.  It has one of the longest spans in the United States. Aquatic Park is a public park in Berkeley, California, United States, located just east of the Eastshore Freeway (Interstate 80) between Ashby and University Avenues.  The Works Progress Administration created the park in the 1930s simultaneously with the nearby Berkeley Yacht Harbor.  Its centerpiece is an artificial mile-long lagoon that was cut off from San Francisco Bay by the creation of a causeway for the Eastshore Highway, during the construction of the approaches to the San Francisco–Oakland Bay Bridge, also in the 1930s.  The lagoon still communicates with the Bay through culverts under the freeway (one in line with Ashby Avenue, the other in line with Grayson Street).  The east shoreline of the lagoon used to be the original shoreline of San Francisco Bay. Interstate 80 (I-80) is a major east–west route of the Interstate Highway System, running between the U.S. states of California and New York.  The highway has its western terminus in San Francisco.  From there it heads east across the Bay Bridge to Oakland, where it turns north and crosses the Carquinez Bridge before turning back northeast through the Sacramento Valley.  I-80 then traverses the Sierra Nevada, cresting at Donner Summit, before crossing into the state of Nevada within the Truckee River Canyon.  The speed limit is at most 65 mph along the entire route instead of the state's maximum of 70 mph and most of the route is in either urban areas or mountainous terrain.  I-80 has portions designated as the Eastshore Freeway and Alan S. Hart Freeway. Interstate 505 (I-505) is an Interstate Highway in California between Interstate 80 in Vacaville and Interstate 5 near Dunnigan.  I-505 is primarily a rural interstate, but travels through Vacaville and the city of Winters.  The interstate is the primary route connecting the San Francisco Bay Area and the northern Sacramento Valley, bypassing Sacramento and its attendant city traffic.  Thus, it is a major route for travelers heading directly from the San Francisco Bay Area to the Pacific Northwest. Interstate 580 (I-580) is an 80-mile (129 km) east–west Interstate Highway in Northern California.  The heavily traveled spur route of Interstate 80 runs from San Rafael in the San Francisco Bay Area to Interstate 5 near Tracy in the Central Valley.  It provides a connection from the Bay Area to the southern San Joaquin Valley and Southern California via Interstate 5, as Interstate 5 bypasses the Bay Area to the east. Interstate 380 (I-380) is a short 1.7-mile (2.7 km) east–west spur Interstate Highway in the San Francisco Bay Area of Northern California, connecting Interstate 280 in San Bruno to U.S. Route 101 near the San Francisco International Airport (SFO).  The highway primarily consists of only three intersections: I-280, El Camino Real (State Route 82), and U.S. 101.  Like nearby I-280, I-380 never connects to Interstate 80, its parent Interstate Highway.  However, there is no rule that says that spur routes need to.  (Similarly, the spur route Interstate 795 branches off from Interstate 695, a beltway around Baltimore, and is only indirectly linked to Interstate 95.) Interstate 80 Business, called the Capital City Freeway in its entirety, is a business loop of Interstate 80 through Sacramento.  Although signed as a business loop the route is actually two connected segments.  The western segment is signed as U.S. Route 50 and carries the unsigned designation of Interstate 305.  The unsigned designation of the eastern segment is State Route 51.  The entire route is a freeway, and carried mainline Interstate 80 through Sacramento until the early 1980s.  Portions of the eastern half were initially grandfathered into the Interstate Highway system; however, plans to upgrade or realign this portion to meet Interstate Highway standards were cancelled.  As such, the I-80 designation through Sacramento was moved to a northern bypass of the city that had previously been signed Interstate 880 (which was later reassigned to what had been State Route 17 between Oakland and San Jose), and the old route of I-80 through downtown was given the current business loop designation. The Carquinez Bridge refers to parallel bridges spanning the Carquinez Strait, forming part of Interstate 80 between Crockett and Vallejo, in the U.S. state of California.  The name originally referred to a single cantilever bridge built in 1927, helping to form a direct route between San Francisco and Sacramento.  A second parallel cantilever bridge was completed in 1958 to deal with the increased traffic.  Later, seismic problems of the 1927 span led to the construction and 2003 opening of a replacement: a suspension bridge officially called the Al Zampa Memorial Bridge (named in the memory of iron worker Al Zampa, who played an integral role in the construction of numerous San Francisco Bay Area bridges).  Currently, the Alfred Zampa Memorial Bridge carries westbound traffic from Vallejo to Crockett, and the 1958 cantilever span carries eastbound traffic.
Answer: 260,000 vehicles