Interstate 680 (California)

A 14-mile (23 km) southbound high-occupancy toll (HOT) lane along I-680 between SR 84 in Alameda County and through the Sunol Grade to SR 237 in Santa Clara County opened on September 20, 2010.[15] Northbound HOT lanes along the same stretch opened in October 2020 but as HOV Lanes. Tolling was halted on I-680 due to the COVID-19 pandemic and will be resumed in 2021.

HOT lanes in both directions also exist on the portion from slightly north of I-580 near the Alameda Contra Costa line to Walnut Creek.

As of October 2020, the HOT lanes' hours of operation is weekdays between 5 a.m. and 8 p.m. Solo drivers are tolled using a variable pricing system based on the time of day. Carpools, motorcycles, and clean air vehicles with 2 or more people are not charged. For clean air vehicles with a solo driver, 50 percent of the posted toll is charged on the Contra Costa Express Lanes,[16] while using the Sunol Express Lanes is free.[17] All tolls are collected using an open road tolling system, and therefore there are no toll booths to receive cash. Each vehicle is required to carry either a FasTrak Flex or CAV (Clean Air Vehicle) transponder, with its switch set to indicate the number of the vehicle's occupants (1, 2, or 3 or more). Solo drivers may also use the FasTrak standard tag without the switch.[16][17]

High-occupancy vehicle (HOV) lanes exist from Concord to the Benicia-Martinez Bridge. The southbound HOV lane was converted in 2020 and extended to meet the existing HOT lane. The HOV lane leading to the Benicia-Martinez Bridge requires a car with 3+ persons, unlike California's regular carpool lanes of 2+ persons.[18] See also: Benicia–Martinez Bridge § Tolling

By the 1920s, a road ran south from Martinez through Walnut Creek, Dublin, Danville, and Sunol to Mission San Jose, where it met State Highway Route 5 (Mission Boulevard, signed over the years as US 48, US 101E, SR 9, and now SR 238). It was not yet paved south of Dublin, where it crossed Mission Pass between the Sunol Valley and the San Francisco Bay basin.[7] The majority of this roadway was added to the state highway system in 1933 as portions of several routes: Route 108 from Mission San Jose to Sunol, Route 107 from Sunol to Walnut Creek, and Route 75 from Walnut Creek to Pleasant Hill.[19][20]

At Martinez, the Martinez-Benicia Ferry took automobiles across the Carquinez Strait to Benicia, where Route 7, one of the original state highways from the 1910 bond issue, led north and northeast past Fairfield towards Sacramento and Oregon.[21] The portion north from Benicia to Fairfield became part of Route 74 in 1935, when Route 7 was realigned to the more direct American Canyon route that is now I-80.[22] None of the aforementioned roads were given state sign route numbers in 1934, when that system was laid out,[23] but by 1937 they had been numbered SR 21.[24] This route began at the intersection of Warm Springs Boulevard and Brown Road in Warm Springs, where Route 5 and Route 69 (SR 17) split, followed Route 5 along Mission Boulevard to Mission San Jose (this part later became an overlap with SR 9), and then continued to US 40 (Route 7) at Cordelia. The routing was very close to the present I-680, following such roads as Pleasanton Sunol Road, San Ramon Valley Boulevard, Danville Boulevard, Main Street in Walnut Creek, Contra Costa Boulevard, and Pacheco Boulevard.[25]

The portion of SR 21 between Pleasant Hill and Martinez was finally added to the state highway system in 1949, as a branch of Route 75.[26] The ferry approach in Benicia became a spur of Route 74 in 1947,[27] and in 1953 it was transferred to Route 75. The same law, effective immediately as an urgency measure, authorized the Department of Public Works to acquire the ferry system, then operated by the city of Martinez, which was planning to shut it down.[28] Ownership was transferred just after midnight on October 6, 1953.[29]

1955 map of the planned Interstates in the San Francisco Bay Area. These early plans essentially called for an interstate loop route that would head south down the San Francisco Peninsula from San Francisco to San Jose, then head north through the eastern cities of the East Bay to Vallejo. This route now basically comprises present-day I-280, I-680, and I-780.

The Bureau of Public Roads approved urban routes of the Interstate Highway System on September 15, 1955, including a loop around the San Francisco Bay, soon numbered I-280 and I-680. The east half (I-680) began at the interchange of US 101 north of downtown San Jose and followed the Nimitz Freeway (SR 17/Route 69, now I-880) to the split at Warm Springs (the present location of SR 262), SR 21 to Benicia, and Route 74 (no sign route number) to I-80 in Vallejo.[30][31][32] The first piece of I-680 freeway built, other than the pre-existing Nimitz Freeway, was in the late 1950s, along the SR 24 overlap between North Main Street in Walnut Creek and Monument Boulevard in Pleasant Hill.[33][34] A southerly extension, bypassing downtown Walnut Creek to South Main Street, opened on March 22, 1960, connecting with the SR 24 freeway to Oakland.[35] In the next decade, the freeway was completed from Vallejo south to SR 238 at Mission San Jose, and the roadway north from Benicia to Fairfield, which became the only remaining piece of SR 21, was also upgraded to freeway standards.[36][37]

In the 1964 renumbering, the legislative designation was changed to Route 680. SR 17 was officially moved to former Route 5 between San Jose and Warm Springs, which had not had a signed designation since the Nimitz Freeway (then I-680) was constructed,[38] but this was instead marked as part of SR 238 (which replaced SR 9 north of Mission San Jose), and SR 17 remained signed along the Nimitz Freeway.[39] This was very short-lived, as the Bureau of Public Roads approved a shift in the south end of I-680 in October 1964.[31] The legislature changed the routes in 1965, swapping Routes 17 and 680 south of Warm Springs, and creating a new SR 262 on the short roadway at Warm Springs where they had overlapped to switch sides.[40][41] However, until I-680 was completed in the early-to-mid 1970s,[36] it remained signed along the Nimitz Freeway, and the old road between San Jose and Warm Springs continued to be marked as SR 238.[37] One more change was made to the routing of I-680: in July 1973, the remainder of SR 21, from Benicia to Fairfield, was added to the Interstate Highway System. This became the new alignment of I-680, and the old route to Vallejo became I-780. The corresponding changes were made by the state legislature in 1976.[42]