Interstate 238 California
Interstate 238 is a short connector between I-880 and I-580 in the East Bay Area of San Francisco Bay. Signed as a north-south route in conjunction with California 238, the freeway portion travels east-west. The cardinal directions allude to the original Mission Freeway plans, which called for SR 238 to continue southeast as a bypass of Hayward, then extend to Interstate 680 just southwest of the Sunol Grade.
Interstate 238 provides part of a truck route between I-580 at Castro Valley and the San Francisco-Oakland Bay Bridge (Interstate 80) in conjunction with the Nimitz Freeway (Interstate 880) through Oakland. This is due to a weight restriction along Interstate 580 (MacArthur Freeway) south of Grand Avenue in Oakland.
Unlike all other three-digit routes within the Interstate Highway System, I-238 has no parent route. The numbering of Interstate 238 was due to the timing of its acceptance into the system; at that time, all “branch” routes of Interstate 80 (180 through 980) were reserved for other routes. Approved by the American Association of State Highway and Transportation Officials (AASHTO) on June 20, 1983, I-238 overlaid a preexisting stretch of State Route 238 between San Leandro and Hayward. The same meeting included the renumbering of Interstate 180 across the Richmond-San Rafael Bridge as an extension of I-580. Renumbering SR 238 as I-180 however was not an option as California does not duplicate its state routes (SR 180 is assigned to a long east-west state route through Fresno).
North End – San Leandro, CA
South End – Hayward, CA
Mileage – 2.23
Cities – Hayward
- Junctions –
Source: December 31, 2018 Interstate Route Log and Finders List
I-238 Annual Average Daily Traffic (AADT)
|Location||Vehicles per day|
|I-580 to Exit 15||158,600|
|Exits 15 to 16A||157,500|
|Exit 16B to I-880||113,400|
Source: 2017 Traffic Volumes – Caltrans Traffic Census Program
Interstate 238 was designated in 1984 as a result of California State Assembly Bill 2741, which modified the route numbering for SR 17 and Interstate 580 in the state highway system. This legislation introduced I-238 and I-980 in Oakland, provided for an extension of I-580 to Marin County, and designated SR 17 as I-880 between San Jose and Oakland. Sign changes due to AB 2741 were implemented along all affected routes by 1985.
Originally California 238 was to continue as a freeway south from Interstate 580 through Hayward. Those plans were shelved indefinitely due to residential opposition and environmental concerns. A court decision in 2003 ended the plans for the recommended Mission Freeway along the green route, with subsequent plans calling instead for the upgrade of Mission Boulevard into an expressway, with potential interchanges at key locations. Stub ramps, since demolished, were previously located along I-680 west of Exit 15 (Washington Boulevard) for the unconstructed freeway.
North End – San Leandro, California
South End – Hayward, California
Interchange sequence sign displaying I-238 to I-880 on westbound Interstate 580. The left lanes of I-580 west default onto Interstate 238 north at Exit 34 in 1.75 miles. I-238 and I-880 provide an alternate route to I-580 for the San Francisco-Oakland Bay Bridge and Interstate 80. Photo taken 02/20/12.
The forthcoming cloverstack interchange joins Interstates 580 and 238 with SR 238 (Foothill Boulevard) to the southeast. There is no access to SR 238 south from I-580 west however. Strobridge Avenue (Exit 35) and Mattox Road instead provides a surface route to Foothill Boulevard south. Photo taken 02/20/12.
Spanning Strobridge Avenue, westbound I-580 separates with three lanes continuing onto the MacArthur Freeway north to eastern Oakland. I-580 splits with SR 13 (Warren Freeway) in 8.5 miles. The Warren Freeway provides a cut off east to SR 24 (Grove Shafter Freeway) for the East Bay Cities of Walnut Creek and Concord. Photo taken 02/20/12.
/ Foothill Blvd north at
Exit 34 carries two lanes south directly to California 238 and Foothill Boulevard. This would have been the Mission Freeway mainline had it been constructed south to Hayward. A single lane ramp otherwise turns west onto Interstate 238 to I-880 for motorists headed south to San Mateo Bridge (SR 92) or San Jose. Photo taken 07/02/06.
Page updated March 5, 2019.