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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. Built in the 1920s and designated in 1955, I-680 begins at a junction with I-280 and US 101 (Bayshore Freeway), and heads northeast and north-northwest through the northeast part of San Jose. After passing SR 237 in Milpitas and SR 262 in Fremont, I-680 abruptly turns northeast (where a connection to a SR 238 freeway was planned) and enters the hills and valleys of the California Coast Ranges. The highway crosses over Mission Pass, also known as the Sunol Grade, and descends into the Sunol Valley, where it meets SR 84 near Sunol. From Sunol, I-680 again heads north-northwesterly through valleys, including the San Ramon Valley, along the Calaveras Fault. Junctions along this portion include I-580 in Dublin and SR 24 in Walnut Creek. Beyond the latter interchange, a three-way directional junction with the SR 24 freeway west to Oakland, I-680 heads north into Pleasant Hill, where SR 242 splits and I-680 again heads northwesterly. After the junction with SR 4 in Martinez, the highway crosses the Carquinez Strait on the Benicia-Martinez Bridge, immediately meeting the east end of I-780 on the Benicia end. The remainder of I-680, from Benicia to I-80 at Fairfield, lies between a hilly area to the west representing the southwestern tip of the Vaca Mountains, and a marshy area (along the Suisun Bay and Cordelia Slough) to the east.〔Google Maps street maps and USGS topographic maps, accessed February 2008 via (ACME Mapper )〕 I-680 is part of the State Scenic Highway System from SR 238 in Fremont north to SR 24 in Walnut Creek,〔California Department of Transportation, (Route 680 - Scenic Highway ), accessed February 2008〕 and is eligible for said system from SR 238 south to the Alameda-Santa Clara County line. ==Route description== The portion of this route from the Route 280/US101 junction to the Santa Clara/Alameda County line is named the Joseph P. Sinclair Freeway, after the District Engineer for District 4 Division of Highways (now Caltrans) from 1952 to 1964 pursuant to Assembly Concurrent Resolution 104, chapter 168 in 1967. Between Alcosta Boulevard and the intersection with I-580, I-680 is officially named the "Officer John Paul Monego Memorial Freeway". It was named after Dublin Police Officer John Paul Monego, who died on December 12, 1998, in the line of duty at the age of 33 years, while responding to a takeover robbery. Named by Senate Concurrent Resolution 60, enrolled August 18, 2000.〔 From Route 24 to Route 4, the route is historically part of "El Camino Sierra" (The Road to the Mountains).〔 The portion of this route from about the Livorna Road interchange in Walnut Creek/Alamo to the Alcosta Blvd. interchange in San Ramon appears to be named the "Donald D. Doyle Highway".〔 While serving in the California Assembly from 1953 to 1958, Donald D. Doyle co-authored the Short-Doyle Mental Health Act with California Senator Alan Short and authored legislation creating the ferry boat transportation system between Benicia and Martinez. The signs indicating this were erected in 1998. Of the above names, only the name ''Sinclair Freeway'' for its designated portion usually appears on maps, and the other portions on maps are always unnamed, referred to as simply ''I-680''.〔 The route begins at U.S. Route 101, where it acts as a continuation of I-280 eastward. From here, it begins its journey northward through San Jose, where it meets the Capitol Expressway, signed as County Route G21.〔 The next exit northbound is State Route 130, which is also known as Alum Rock Avenue. As it continues through Santa Clara County, it meets numerous local roads before interchanging with the Montague Expressway. Here, it exits San Jose and enters the city of Milpitas, California, where it meets State Route 237, often referred to as Calaveras Boulevard. After one more intersection, I-680 exits Santa Clara County and enters Alameda County.〔 In Alameda County, the freeway begins in the city of Fremont, where it intersects State Route 262. Continuing through the city, it meets Mission Boulevard at State Route 238 before exiting the city. Amid Alameda County, it abruptly turns northeastward and enters a hilly area, where it crosses over Mission Pass, and descends into the Sunol Valley, where it joins State Route 84 for a short while. Afterwards, it enters Pleasanton and interchanges with Interstate 580. It enters Dublin for a short segment before exiting the county and entering Contra Costa County.〔〔 Upon entering Contra Costa County, the route meets numerous local roads through the cities of San Ramon, Danville, and Alamo before entering Walnut Creek, where it meets State Route 24.〔 I-680 then enters Pleasant Hill for a short time and Concord, where it meets State Route 242. Upon exiting Concord, it meets State Route 4. It then enters Martinez, where it follows the Benicia-Martinez Bridge over the Carquinez Strait, on which the route crosses the county line and enters Benicia in Solano County.〔〔〔 In Benicia, I-680 interchanges with Interstate 780. It then exits the city and enters Fairfield, where it meets Interstate 80, where the route finds its north terminus.〔 In the wake of the September 11 Attacks, a U.S. flag was painted on a large piece of concrete on a hill along the Sunol Grade. It stayed there for nine years before Caltrans painted it over, as the mural had been painted on without authorization. Due to this action being taken shortly before July 4th, 2010, and also due to the mural's fame, this was met with controversy. The flag was replaced shortly later. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Interstate 680 (California)」の詳細全文を読む スポンサード リンク
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