|Defined by Streets and Highways Code § 384|
|Maintained by Caltrans|
|Length||96 mi (154 km)|
|Niles Canyon Road between SR 238 in Fremont and I-680 near Sunol|
|West end||SR 1 at San Gregorio|
|East end||I-580 in Livermore|
|South end||SR 12 in Rio Vista|
|North end||Near Levee Access Road at the southern city limits of West Sacramento|
|Counties||San Mateo, Alameda, Solano, Yolo|
State Route 84 (SR 84) is a state highway in the U.S. state of California that consists of two unconnected segments, one in the San Francisco Bay Area and the other primarily in the Sacramento-San Joaquin River Delta area.
The first section is an east–west arterial road running from SR 1 in San Gregorio to Menlo Park, across the Dumbarton Bridge through Fremont and Newark and ending at I-580 in Livermore. The segment between Marsh Road and the Dumbarton Bridge has been upgraded to an expressway and is known as the Bayfront Expressway. The segment from the eastern end of the Dumbarton Bridge to the interchange with I-880 has been upgraded to a freeway.
The other section is a north-south arterial road that begins at SR 12 in Rio Vista, passes through Ryer Island (where it connects to SR 220), and ends in West Sacramento. The Ryer Island Ferry provides the crossing over Cache Slough from Rio Vista to Ryer Island. The ferry is a diesel-powered boat operated by Caltrans, and is in operation twenty-four hours per day and charges no toll. There are no plans to connect the two unconnected segments of SR 84 at this time.
The route begins at SR 1 on the Pacific coast near San Gregorio. It then heads northeast through San Mateo County, following San Gregorio Road and La Honda Road and crossing the Santa Cruz Mountains. As it enters Woodside, it intersects SR 35, also known as Skyline Boulevard. From the juncture of La Honda Road with Portola Road to US 101 it follows Woodside Road. After intersecting I-280, it enters Redwood City, where it intersects SR 82, which carries El Camino Real through the South Bay. A few miles later, it interchanges with US 101, which it overlaps for a few miles.
Upon routing eastward, it enters the city of Menlo Park as an expressway, called the Bayfront Expressway, which features traffic signals at Menlo Park streets, at driveways serving Facebook headquarters, and at intersections with SR 114 and SR 109. The Marsh Road intersection, in 2013, was the site where a car fatally struck cyclist Sam Felder, a Facebook employee. The SR 114 (Willow Road) intersection was the site of a car crash in which author David Halberstam was killed on April 23, 2007.
SR 84 then becomes a freeway at the south end of San Mateo County as it crosses as the Dumbarton Bridge over the San Francisco Bay. Midway over the bridge, it enters Alameda County. In Alameda County, it runs northward through the city of Newark, where it begins a concurrency southwards with I-880 for about one mile. Both interchanges with I-880 are partial cloverleaf interchanges. Upon separation, however, the route is not built to freeway standards as it enters the city of Fremont, following the streets of Thornton Ave, Fremont Blvd, Peralta Blvd, and Mowry Ave, which after, it has a short concurrency northwards with SR 238.
SR 84 then leaves Fremont through the historic Sunol Valley. Parts of the valley are extremely narrow and are referred to as Niles Canyon; this part of the route is officially a scenic route. After exiting the valley, it begins an overlap with I-680. After separating, it runs through Vallecitos Valley. It then goes over grasslands until it reaches a pass, then enters the city of Livermore with Ruby Hill development on the left. SR 84 then runs along Isabel Ave until it meets I-580, as the end of its southern section. SR 84 is unconstructed from I-580 to SR 12.
The second section of SR 84 starts in Rio Vista at SR 12. It then follows the Ryer Island Ferry, which carries the route across the Cache Slough. When it leaves the ferry, it intersects SR 220. It continues northward and meets the end of state maintenance at the West Sacramento city limit, about six miles east of an intersection with CR E19. It then enters the city of West Sacramento in Yolo County. It then interchanges with I-80 Business, also signed as US 50. As it continues northward, it ends at I-80. From north of West Sacramento, SR 84 has been relinquished and was given to the city of West Sacramento in 2003.
SR 84 is part of the California Freeway and Expressway System, but is not part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. SR 84 is eligible for the State Scenic Highway System, and is designated as a scenic highway by the California Department of Transportation from SR 238 to I-680 in Alameda County, meaning that it is a substantial section of highway passing through a "memorable landscape" with no "visual intrusions", where the potential designation has gained popular favor with the community.
Until recent years, all of CA-84 consisted of narrow, two-lane roads in California. This has remained almost unchanged except for urban areas and the CA-84 widening project in the Tri-Valley.
Route 84 is legally defined to continue from I-580 to SR 4 in Antioch, but there are currently no plans in place to bridge the gap at this time. A plan to build a $600 million toll road called the Mid-State Tollway along the proposed route was suspended in 2001 due to local opposition.
In the late 2000s and 2010s, a widening project began on Route 84 from I-680 near Sunol to I-580 in Livermore. This included a better connection between Stanley Boulevard and Isabel Avenue. The project was to be done in five phases:
Costs were estimated to be between $400 and $500 million.
As of mid 2019, phases 1, 2, 3 and 4 are complete. This still leaves the southern section of CA 84 in its original condition.
Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage. R reflects a realignment in the route since then, M indicates a second realignment, L refers an overlap due to a correction or change, and T indicates postmiles classified as temporary (). Segments that remain unconstructed or have been relinquished to local control may be omitted. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.
|San Gregorio||0.00||SR 1 - Half Moon Bay, Santa Cruz||Southwest end of SR 84|
|Woodside||14.95||SR 35 (Skyline Boulevard) - San Francisco, Santa Cruz|
|21.54||I-280 (Junipero Serra Freeway) - San Francisco, San Jose||Interchange; I-280 exit 25|
|Redwood City||24.70||SR 82 (El Camino Real)||Interchange|
|US 101 north (Bayshore Freeway) / Seaport Boulevard - San Francisco||Interchange; west end of US 101 overlap; US 101 exit 408|
|||West end of freeway on US 101|
|Menlo Park||||East end of freeway on US 101|
|US 101 south (Bayshore Freeway) / Marsh Road - San Jose, Atherton||Interchange; east end of US 101 overlap; US 101 exit 406|
SR 114 (Willow Road) to US 101 south - Menlo Park
|R28.19||SR 109 (University Avenue) - East Palo Alto|
|||West end of freeway|
|||Ravenswood, S.F. Bay National Wildlife Refuge|
|San Francisco Bay||R29.25-|
|Dumbarton Bridge (westbound toll only)|
|Newark||R3.75||36||Thornton Avenue, Paseo Padre Parkway|
|R4.88||37||Newark Boulevard, Ardenwood Boulevard|
|38||I-880 north (Nimitz Freeway) / Decoto Road - Oakland||Interchange; west end of I-880 overlap; I-880 exit 21|
|Fremont||||East end of freeway on I-880|
|I-880 south (Nimitz Freeway) / Thornton Avenue - San Jose||Interchange; east end of I-880 overlap; I-880 exit 19|
|SR 238 south (Mission Boulevard) - San Jose||West end of SR 238 overlap|
|SR 238 north (Mission Boulevard) / Niles Boulevard - Hayward, Union City||East end of SR 238 overlap|
|Sunol||16.93||Sunol (Main Street)||Interchange; eastbound exit and westbound entrance|
|I-680 south / Calaveras Road - Fremont, San Jose||Interchange; west end of I-680 overlap; I-680 north exit 21A, south exit 21|
|||||West end of freeway on I-680|
|I-680 north - Walnut Creek, Sacramento||East end of I-680 overlap; I-680 north exit 21B, south via a U-turn at exit 21|
|||||East end of freeway|
|Pleasanton||23.56||Vallecitos Road - Downtown Livermore||Former SR 84 east|
|||I-580 / Isabel Avenue to Portola Avenue - Oakland, Stockton||Interchange; northeast end of southwestern segment of SR 84; I-580 exit 51|
|Gap in route|
|Rio Vista||0.13||SR 12 / Front Street - Lodi, Fairfield, Rio Vista||Interchange; south end of northern segment of SR 84|
|||2.49||Ryer Island Ferry across Cache Slough|
|||7.25||SR 220 east - Ryde|
|||9.53||CR E19 (Clarksburg Road) - Clarksburg|
|West Sacramento||15.69||North end of state maintenance at West Sacramento city limit|
|R21.78||US 50 (Capital City Freeway) - San Francisco, Sacramento||Interchange; former I-80; US 50 exit 3|
|21.84||To Capitol Mall (SR 275, Tower Bridge Gateway)||Interchange; former US 40 / US 99W|
|22.06||West Capitol Avenue||Former US 40 / US 99W|
|22.68||Sacramento Avenue, Kegle Drive||Sacramento Avenue was former SR 16 east|
|23.47||Sunset Avenue - Woodland||Former SR 16 west|
I-80 to I-5 - Reno, San Francisco
|Interchange; former I-880; I-80 exit 83|
|24.05||Reed Avenue||Continuation beyond I-80|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|