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Interstate 680 or I -680 is an Interstate Highway in the U.S. state of California. The highway forms a north-south route along the east side of the San Francisco Bay Area metropolitan area. The highway runs from San Jose to Cordelia and is 114 kilometers long. I-680 is known in part as the Sinclair Freeway.
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I-680 at Alamo, between Dublin and Walnut Creek.
Congestion on the ‘Sunol Grade’ north of San Jose.
The freeway begins at an interchange with US 101 and Interstate 280 in San Jose, the largest city in the metropolitan area with 1 million inhabitants. There are 2×4 lanes available and the highway turns north. One passes through the eastern neighborhoods of San Jose, and many connections are shaped like a cloverleaf. You then pass through the suburb of Milpitas. Here, I-680 parallels Interstate 880. The next major city is Fremont, the 4th city of the conurbation. In Fremont, I-680 suddenly turns with a wide bend to the east, the wide median strip indicates that a highway should once have gone straight here.
One then enters the mountains, which encircle the San Francisco Bay on all sides. The highway leads here over the infamous ‘Sunol Grade’. After about 16 kilometers you enter the row of eastern suburbs, of which Pleasanton is the first. This is one of the richest cities in the United States. I-680 will then have 2×3 lanes. At Dublin, one crosses Interstate 580, which runs east from Oakland. This is the first opportunity to head east after San Jose. One passes through the suburbs of San Ramon and Danville. These are the more expensive suburbs of the conurbation. In Walnut Creek one crosses State Route 24, which leads to Oakland. The section through Walnut Creek is a lot busier due to traffic from SR-24 and also has 2×5 lanes. At Pleasant Hill, State Route 242 exits, which also provides heavy traffic to the eastern suburbs of Concord, Pittsburg, and Antioch. Larger industrial estates are located in Concord between I-680 and SR-242.
At Pacheco, one crosses State Route 4, which runs from Hercules to Antioch. Then you arrive in the suburb of Martinez. Here one crosses the Carquinez Strait, a strait between San Pablo Bay and Suisun Bay. This goes through the Benicia-Martinez Bridge. Immediately after, in Benicia, Interstate 780 exits, which leads to Vallejo. Parallel to I-680 is Suisun Bay, where about 80 old naval ships are rusting in the water. On the other side of the highway is an oil refinery. I-680 ends a little further in Cordelia on Interstate 80 to Sacramento.
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The highway was first planned in 1955, when a ring road around the San Francisco area was proposed. This was at the same time as I-280 to San Francisco. In the late 1950s, the first section between Walnut Creek and Pleasant Hill was opened. On March 22, 1960, a short section connecting State Route 24 opened the highway to Oakland. During the 1960s, the highway was then extended north and south. In 1962, the Benicia-Martinez Bridge opened over the Carquinez Strait, eliminating the last car ferry service in the region. The last section of the highway was opened at San Jose in the early 1970s.
Between 1986 and 1989, part of I-680 in Dublin was widened. In 1990, the highway between Fremont and Pleasanton was widened. In 1994 the section between Dublin and Walnut Creek followed. Between 1995 and 1998, the route between Walnut Creek and Concord was widened.
One of the biggest modifications was the construction of a second Benicia-Martinez Bridge, which opened on August 25, 2007. The original 1962 bridge cost $25 million, the new 2007 bridge cost a whopping $1.3 billion, while the original estimates were $300 million. Like many projects in the region, this bridge also got out of hand in terms of delays and costs.
I-680 has the Bay Area’s longest HOV lane, a 40-mile car pool lane between Martinez and San Ramon. The last part of this opened on August 24, 2020.
On September 20, 2010, a 23-kilometer HOT lane in the San Jose area opened to traffic, but only heading south. Between 2018 and 2020, the first phase of the express lane to the north was constructed, from Auto Mall Parkway to CA-84, over the notoriously congestion-prone Sunol Grade. Between October 2018 and September 2021, a 19-kilometer express lane was built south between Martinez and Walnut Creek.
I-680 over the Sunol Grade between Pleasanton and Fremont has been one of the most congested highways in the United States, due to Silicon Valley’s many jobs, but exorbitant housing prices there keep commuters living in the interior of Alameda County.. Towards the south, an HOV lane has now been converted into a HOT lane, but towards the north, only 3 lanes were available. Work began in early 2018 to build the first phase of an express lane northbound between the Auto Mall Parkway and CA-84. The extra lane opened on October 29, 2020, first as a carpool lane, but in 2021 as an express lane with toll.
|45A Main Street||46B||2 km||00-00-1960|
|65 Goodyear Road||70||8 km||00-00-1961|
|16 Mission Boulevard||21 Vallecitos Road||8 km||00-00-1963|
|38 Sycamore Valley Road||45A Main Street||11 km||00-00-1964|
|30||31 Alacosta Boulevard||2 km||00-00-1965|
|31 Alacosta Boulevard||38 Sycamore Valley Road||11 km||00-00-1966|
|58||65 Goodyear Road||11 km||00-00-1966|
|21 Vallecitos Road||30||14 km||00-00-1967|
|8||16 Mission Boulevard||13 km||00-00-1971|
|Exit 1||San Jose ( I-280 )||159,000||148,000||165,000|
|Exit 2||San Jose (King Road)||225,000|
|exit 8||San Jose ( SR-237 )||144,000||130,000||146,000|
|Exit 30||Pleasantton ( I-580 )||148,000||167,000||179,000|
|exit 46||Walnut Creek ( SR-24 )||246,000||256,000||261,000|
|Exit 50||Concord ( SR-242 )||238,000||230,000||267,000|
|exit 53||Martinez ( SR-4 )||132,000||112,000||143,000|
|exit 58||Benicia ( I-780 )||100,000||98,000||85,000|
|Exit 71||Cordelia ( I-80 )||60,000||57,000||83,000|