California State Route 84
|Defined by S&HC § 384|
|Maintained by Caltrans|
|Length:||96 mi (154 km)|
|West end:||SR 1 at San Gregorio|
| I-280 at Woodside
US 101 in Redwood City
I-880 in Fremont
SR 238 in Fremont
I-680 near Sunol
|East end:||I-580 in Livermore|
|South end:||SR 12 in Rio Vista|
|North end:||I-80 in West Sacramento|
State Route 84 (SR 84) is a split-section California State Highway consisting of two sections. The first section is an east–west arterial road running from San Gregorio to Menlo Park, across the Dumbarton Bridge through Fremont and Newark and ending at I-580 in Livermore. The route overlaps the freeway segment of U.S. 101 between Woodside Road in Redwood City and Marsh Road in Menlo Park. 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 western 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 Route 12 in Rio Vista, passes through Ryer Island (where it connects to Route 220), and ends at the Interstate 80 interchange in West Sacramento. However, plans are underway to turn maintenance of SR 84 through West Sacramento to that city.
A ferry provides the crossing over Cache Slough from Rio Vista to Ryer Island. The ferry, a diesel-powered boat operated by Caltrans, is in operation twenty-four hours per day and charges no toll.
Route 84 is legally defined to continue from I-580 to Route 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.
Route description 
The route begins at SR 1 in San Gregorio. It then heads northward through San Mateo County as it enters Woodside, where it intersects SR 35, also known as Skyline Boulevard, and interchanges with Interstate 280 (California). It then enters Redwood City, where it intersects SR 82, which carries El Camino Real through the South Bay. A few miles later, it interchanges with U.S. Route 101, which it overlaps for several miles. Upon exiting, it enters the city of Menlo Park as an expressway, where it intersects SR 114 and SR 109 at intersections controlled by traffic lights. The SR 114 (Willow Road) intersection was the site of the car crash in which author David Halberstam was killed on April 23, 2007.
In Alameda County, it runs northward through the city of Newark, where it begins a concurrency with Interstate 880. Both interchanges with Interstate 880 are partial cloverleaf interchanges, meaning that through traffic on Route 84 encounters traffic lights while joining and leaving I-880. Upon separation, the route loses its freeway status as it enters the city of Fremont, where it has a short concurrency with SR 238. There are plans to construct a new parkway between the I-880 interchange and Mission Boulevard (CA 238).
It then leaves Fremont through the historic Sunol Valley. After exiting the valley, it begins an overlap with I-680. After separating, it runs for several miles over a pass, then enters the city of Livermore; it runs along Isabel Ave until it meets I-580, as the end of its southern section.
Upon reappearing, the route begins at SR 12 in Rio Vista. In 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 U.S. Route 50. As it continues northward, it ends at Interstate 80.
Major intersections 
Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, and do not necessarily reflect current mileage. R reflects a realignment in the route since then. 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|
|Woodside||14.95||SR 35 (Skyline Boulevard) – San Francisco, Santa Cruz|
|21.54||I-280 (Junipero Serra Freeway) – San Francisco, San Jose||Interchange|
|Redwood City||22.68||Alameda de las Pulgas|
|24.70||SR 82 (El Camino Real)||Interchange|
|25.06||Middlefield Road – Downtown Redwood City|
|US 101 north (Bayshore Freeway) / Seaport Boulevard – San Francisco||Interchange; west end of US 101 overlap|
|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|
|R27.66||SR 114 (Willow Road) – Menlo Park|
|R28.19||SR 109 (University Avenue) – East Palo Alto|
|West end of freeway|
|Dumbarton Bridge over San Francisco Bay|
|Newark||R3.75||36||Thornton Avenue, Paseo Padre Parkway|
|R4.88||37||Newark Boulevard, Ardenwood Boulevard|
|I-880 north (Nimitz Freeway) / Decoto Road – Oakland||Interchange; west end of I-880 overlap|
|Fremont||East end of freeway on I-880|
|I-880 south (Nimitz Freeway) / Thornton Avenue – San Jose||Interchange; east end of I-880 overlap|
|8.02||Thornton Avenue, Fremont Boulevard|
|8.33||Fremont Boulevard, Peralta Boulevard|
|9.92||Mowry Avenue – Civic Center|
|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|
|West end of freeway on I-680|
|I-680 north – Walnut Creek, Sacramento||East end of I-680 overlap; no eastbound entrance|
|East end of freeway|
|Pleasanton||23.56||Vallecitos Road – Downtown Livermore||Former SR 84 east|
|I-580 / Isabel Avenue – Oakland, Stockton||Interchange|
|Gap in route|
|Rio Vista||0.13||SR 12 / Front Street – Lodi, Fairfield||Interchange|
|2.49||Ryer Island Ferry across Cache Slough|
|7.25||SR 220 east – Ryde|
|12.08||Ryer Road East – Ryde|
|4.57||Courtland Road – Courtland, Rio Vista|
|9.53||CR E19 (Clarksburg Road) – Clarksburg|
|West Sacramento||15.69||North end of state maintenance at West Sacramento city limit|
|19.85||Lake Washington Boulevard|
|R21.78||I-80 Bus. (Capital City Freeway, US 50) – San Francisco, Sacramento||Interchange; former I-80|
|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|
|24.05||I-80 to I-5 – Reno, San Francisco||Interchange; former I-880|
|24.05||Reed Avenue||Continuation beyond I-80|
- Indicates that the postmile represents the distance along US 101 rather than SR 84.
- Indicates that the postmile represents the distance along I-880 rather than SR 84.
- Indicates that the postmile represents the distance along SR 238 rather than SR 84.
- Indicates that the postmile represents the distance along I-680 rather than SR 84.
- January 1, 2006 California Log of Bridges on State Highways
- CA Codes (shc:250-257)
- CA Codes (shc:260-284)
- "Officially Designated State Scenic Highways and Historic Parkways". California Department of Transportation. December 7, 2007. Retrieved June 22, 2011.
- California Department of Transportation, State Truck Route List (XLS file), accessed February 2008
- California Department of Transportation, Log of Bridges on State Highways, July 2007
- California Department of Transportation, All Traffic Volumes on CSHS, 2003, 2005, and 2006
- California Department of Transportation, California Numbered Exit Uniform System, SR-84 Northbound and SR-84 Southbound, accessed February 2008
- California @ AARoads - State Route 84
- Caltrans: Route 84 highway conditions
- Caltrans: Mid-State Tollway
- California Highways: SR 84
- Live Toll Prices for Dumbarton Bridge