Interstate 380 California


Interstate 380 is the short, busy connector between Interstate 280 at San Bruno with U.S. 101 (Bayshore Freeway) at South San Francisco and San Francisco International Airport (SFO). It consists of a six lane freeway with auxiliary lanes added between on and off-ramps.

Interstate 380 connects with the airport via reconstructed ramps that parallel U.S. 101 for a short distance. This connection was upgraded in the early 2000s as part of an expansion project at San Francisco International Airport (SFO) that included a new terminal. An extension of the Bay Area Rapid Transit (BART) system enhanced access to the airport. Ramps for this new rail corridor are commingled with those for the freeways.


I-380 was established by the December 1968 Federal Aid Highway Act, and it was constructed by the early 1970s to replace then-California 186. Designated the Portola Freeway at the time of its construction, it was given a second name in the 1990s as the Quentin Kopp Freeway.

Plans previously called for extending Interstate 380 west from its current terminus at Interstate 280 to California 1 at Pacifica. However, such a freeway was heavily disputed due to environmental, terrain, and traffic impact issues. Provisions for the extension were however made at the interchange between I-280 and I-380. These are visible by travelers headed westbound on Interstate 380. Exit numbers along Interstate 380 start at five and reference the unconstructed alignment from Pacifica.

Throughout the latter half of the 20th century, studies also called for additional crossings of San Francisco Bay. One of the corridors considered was a bridge system linking Interstate 380 on the San Francisco Peninsula with Interstate 238 at the East Bay. The crossing was envisioned to span the bay near its widest point. Several obstacles, including funding and mitigating for environmental concerns, prevented the proposed route from moving forward. The I-380 proposal was separate from the "Southern Crossing", a cross bay route planned for further north closer to San Francisco. Dan Faigin provides more detailed information on the crossing on California Highways.

Highway Guides

Western Terminus - Interstate 280 - San Bruno, California
Perspective from Interstate 380 west
Westbound Interstate 380 approaches the junction with Interstate 280 (Father Junipero Serra Freeway). The forthcoming directional T interchange includes provisions to extend I-380 from I-280 west to California 1. A separate proposal involving the unused roadway called for extending I-380 west to nearby California 35 (Skyline Drive). Photo taken 03/26/16.
The Interstate 380 mainline defaults motorists onto I-280 north with three lanes. A left-hand flyover takes drivers south to San Jose otherwise. Photo taken 11/26/04.
Traffic separates into the flyovers for Interstate 280 as I-380 ends. Photo taken 11/26/04.
Historical Perspective from Interstate 380 west
Button copy signs for Interstate 280 were replaced by 2008 to display Exits 5B/A. Photo taken 11/26/04.
The three lane off-ramp for I-280 passed over Cherry Avenue and separated with three lanes north to San Francisco and two south to San Jose. Photo taken 11/26/04.
Perspective from Interstate 280 south
This interchange sequence sign along southbound Interstate 280 is the first indication of the pending interchange with Interstate 380 east to U.S. 101. Photo taken 11/26/04.
Southbound Interstate 280 approaches Exit 43A for Interstate 380 east to San Francisco International Airport (SFO). Exit 43B, a distributor roadway connecting with Sneath Lane and San Bruno Avenue, would have served the western extension of I-380 had it had been constructed. Photo taken 11/26/04.
An auxiliary lane accompanies I-280 south from Avalon Drive through to the back to back ramps for Sneath Lane (Exit 43B) and Interstate 380 (Exit 43A) east. Photo taken 11/26/04.
Ramps depart for Sneath Lane, San Bruno Avenue and Interstate 380 east from I-280 south. Note the covered up shield for Sneath Lane / San Bruno Avenue (Exit 43B). Photo taken 11/26/04.
Interstate 380 is the best route from Interstate 280 to San Francisco International Airport (SFO). It is the lone freeway linking I-280 with U.S. 101 between San Francisco and San Mateo. Photo taken 11/26/04.
Taking Exit 43A, a two-lane ramp carries drivers from I-280 south to I-380 east below an abandoned overpass built for the western extension. Photo taken 11/26/04.
Eastern Terminus - U.S. 101 - South San Francisco, California
Perspective from Interstate 380 east
Exit 5 quickly departs Interstate 380 east for California 82 (El Camino Real) into San Bruno. An unused roadway remains in place to the left from the scuttled I-380 extension. Travelers otherwise advance toward the cloverstack interchange with U.S. 101. Photo taken 11/26/04.
The I-380 mainline defaults onto ramps for both North Access Road and South Airport Boulevard. The number three lane transitions onto northbound U.S. 101 through South San Francisco while a two-lane off-ramp to the right leads to U.S. 101 south and the passenger terminal of SFO Airport. Photo taken 11/26/04.
A viaduct carries Interstate 380 over three avenues and a railroad corridor as Exit 6A partitions for U.S. 101 south to SFO Airport and San Jose. The mainline connection to North Access Road is assigned Exit 7. It serves a variety of aviation-oriented businesses along the northern periphery of the airport property. Photo taken 11/26/04.
Now on the transition ramp from I-380 east to U.S. 101 south, the two lane exit immediately splits with a slip ramp leading to the passenger terminal flyover ramps. Photo taken 11/26/04.
Perspective from U.S. 101 south
U.S. 101 travels through an industrial area of South San Francisco into the cloverstack interchange (Exit 423) with Interstate 380 west and the ramps to San Francisco International Airport (SFO). Photo taken by Joel Windmiller (04/07/02).
Perspective from San Francisco International Airport Access Road west
Departing from the passenger terminal of San Francisco International Airport, these signs direct motorists to the freeway system. A direct flyover links the terminal area with Interstate 380 west. Photo taken 11/29/04.
Interstate 380 offers a quick route between the SFO Airport and Interstate 280 for the western half of San Francisco. The route, in conjunction with California 1 (19th Avenue), allows travelers bound for Marin County and points north to use the Golden Gate Bridge without having to drive through the city on Van Ness Avenue (U.S. 101). Photo taken 11/29/04.
While the previous two sign bridges were placed by the airport, the next sign bridge is a button copy sign that was Caltrans's standard sign until 1999. The destination for Interstate 380 is San Bruno, but it is also the best route to Pacifica and Daly City, as well as western San Francisco. Photo taken 11/29/04.
Ramps from both Airport Access Roads combine and turn north to run parallel with U.S. 101 (Bayshore Freeway) north directly to Interstate 380 west. Photo taken 11/29/04.
Perspective from U.S. 101 north
U.S. 101 (Bayshore Freeway) runs along the west side of San Francisco International Airport (SFO) as it travels between San Jose and San Francisco. Travelers continue 1.25 miles beyond the passenger terminal exit to Exit 423B for Interstate 380 west. Photo taken 03/26/16.
As U.S. 101 passes under the tangle of ramps associated with the airport interchange, guide signage for I-380 simply references the connection with Interstate 280 (Junipero Serra Freeway). Photo taken 03/26/16.
A two lane flyover parallels the northbound lanes of U.S. 101 from the passenger terminal of SFO Airport directly to Interstate 380 west. Back to back ramps depart otherwise for San Bruno Avenue (Exit 423A) to various car rental and air cargo facilities and I-380 west to San Bruno. Photo taken 03/26/16.
A two-lane off-ramp departs just to the north of the San Bruno Avenue exit for Interstate 380 west. I-380 connects U.S. 101 with parallel California 82 (El Camino Real) in addition to I-280. Photo taken 03/26/16.
San Bruno Avenue spans U.S. 101 (Bayshore Freeway) as Exit 423B parts ways for Interstate 380 west. The adjacent flyover lowers and separates into slip ramps for both I-380 west and the U.S. 101 c/d roadway for San Bruno Avenue. Photo taken 03/26/16.
Perspectives from Airport Boulevard
Airport Boulevard stems north from the intersection of San Bruno Avenue and McDonnell Road to parallel U.S. 101 through to Gateway Boulevard at San Mateo Avenue. The arterial route connects the car rental facilities of SFO Airport with the westbound beginning of I-380 as well. Photo taken 11/26/04.
Airport Boulevard sees a direct ramp for I-380 west as flyovers connecting North Access Road with U.S. 101 pass overhead. An access road to the east provides access to the U.S. 101 ramps from adjacent North Access Road. Photo taken 11/26/04.
Airport Boulevard south at the freeway entrance for Interstate 380 west and U.S. 101 north. Photo taken 03/26/16.
Following the access road east from Airport Boulevard, motorists approach a parking garage and the intersection with North Access Road and Interstate 380 west. Photo taken 11/26/04.
North Access Road west transitions directly onto Interstate 380 west as flyovers depart for U.S. 101 (Bayshore Freeway). North Access Road east encircles SFO Airport through to air cargo facilities. Photo taken 11/26/04.
Perspective from Interstate 380 west
North Access Road west transitions to Interstate 380 beyond the traffic signal with the Airport Boulevard connector road. Single lane flyovers follow to carry motorists west to San Bruno, south to San Jose and north to San Francisco. Photo taken 11/26/04.
The on-ramp from Airport Boulevard provides access to both Interstate 380 west and U.S. 101 north. Photo taken 03/26/16.

Page Updated April 5, 2016.

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State California
Mileage 3.30
Cities San Bruno, San Francisco
Junctions I-280
Source: December 31, 2017 Interstate Route Log and Finders List
I-380 California Annual Average Daily Traffic

Begin Milepost Location To: AADT
4.70 I-280 begin fwy SR 82 128,000
5.47 SR 82 South San Francisco (6.37) 150,000
Source: Caltrans, Traffic Operations Program - Traffic and Vehicle Data Systems [2002]
The ultimate extent of Interstate 380 proposed in 1966.
Construction of Interstate 380 displaced the full cloverleaf interchange between U.S. 101 (Bayshore Freeway) and San Bruno Avenue. A portion of the original footprint remains visible on the west side of the junction today.