Interstate 380 California
Overview
Interstate 380 is a busy connector linking I-280 at San Bruno with U.S. 101 (Bayshore Freeway) at South San Francisco and San Francisco International Airport (SFO). I-380 constitutes a six lane freeway with auxiliary lanes added between entrance and exit ramps.
Ramps at San Francisco International Airport (SFO) were upgraded in the early 2000s as part of an expansion project that included a new terminal. An extension of the Bay Area Rapid Transit (BART) system, which commingles with the I-380 ramps, enhanced access to the airport.
History
HistoryI-380 was established by the December 1968 Federal Aid Highway Act. It was constructed by the early 1970s to replace California State Route 186. Designated the Portola Freeway, it was also named the Quentin Kopp Freeway in the 1990s.
Plans previously called for extending Interstate 380 west from I-280 to California 1 at Pacifica. Heavily disputed due to environmental, terrain, and traffic impact issues, the roadway remains unbuilt. Provisions were however made at the interchange joining I-280 and I-380 and exit numbers start at five, referencing 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 considered from San Francisco to Alameda.
Route Information
East End – South San Francisco, CA
West End – San Bruno, CA
Mileage – 3.30
Cities – San Bruno, South San Francisco
- Junctions –
Source: December 31, 2021 Interstate Route Log and Finders List
I-380 Annual Average Daily Traffic (AADT)
| Location | Vehicles per day |
|---|---|
| I-280 to Exit 5 | 143,900 |
| Exits 5 to 6 | 169,100 |
| US 101 to S Airport Rd | 23,700 |
Source: 2017 Traffic Volumes – Caltrans Traffic Census Program
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.
 Photo Guides
 Photo GuidesEast End 
/ N Access Road – South San Francisco, California
East at 
/ North Access Road
Leading away from I-280, Exit 5 quickly departs Interstate 380 east for California 82 (El Camino Real) in San Bruno. An unused roadway remains in place between the I-380 roadways from the unbuilt extension. 07/11/18
Interstate 380 advances east from El Camino Real toward the cloverstack interchange (Exit 6) with U.S. 101. 07/11/18
The I-380 mainline defaults onto ramps for both North Access Road and South Airport Boulevard. The ensuing exit departs for both U.S. 101 south and the passenger terminal at SFO Airport. Photo taken 07/11/18.
A two lane flyover (Exit 6B) follows from Interstate 380 east for northbound U.S. 101 through South San Francisco. 07/11/18
A viaduct extends east along Interstate 380 over three streets and a railroad corridor to North Access Road (Exit 7) and South Airport Boulevard. 07/11/18
The signalized end of the freeway connects I-380 with North Access Road to a variety of aviation-oriented businesses along the northern periphery of the airport property. 07/11/18
South at
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 by Joel Windmiller (04/07/02)
San Francisco International Airport Access Road west at
Departing from the passenger terminal of San Francisco International Airport, these signs direct motorists to the freeway system. 07/23/16
A direct flyover links the SFO Airport terminal area with Interstate 380 west. 07/23/16
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 to San Bruno, Pacifica and Daly City. I-380 offers a quick route between SFO Airport and Interstate 280 for the western half of San Francisco. I-280, in conjunction with SR 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). 11/29/04
North at
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. 03/26/16
U.S. 101 passes under the multi level interchange with SFO Airport one mile ahead of I-380 west to Interstate 280 (Junipero Serra Freeway). 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. Succeeding ramps depart from the Bayshore Freeway mainline for San Bruno Avenue (Exit 423A) to various car rental and air cargo facilities and I-380 west to San Bruno. 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. 03/26/16
Airport Boulevard / North Access Road at
Airport Boulevard stems north from the intersection of San Bruno Avenue and McDonnell Road and parallels U.S. 101 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. 11/26/04
A direct ramp joins Airport Boulevard with I-380 west as flyovers connecting North Access Road with U.S. 101 pass overhead. An access road to the east provides links with the U.S. 101 ramps from adjacent North Access Road. 11/26/04
Airport Boulevard south at the freeway entrance for Interstate 380 west and U.S. 101 north. 03/26/16
The on-ramp from Airport Boulevard provides access to both Interstate 380 west and U.S. 101 north. 03/26/16
N Access Road connects Airport Boulevard with the Park SFO parking garage and the westbound beginning of Interstate 380. 07/15/23
N Access Road westbound transitions directly onto Interstate 380 where flyovers depart for U.S. 101 (Bayshore Freeway). N Access Road east encircles SFO Airport to air cargo facilities. 07/15/23
N Access Road west transitions to Interstate 380 beyond the traffic signal with the Airport Boulevard connector road. Single lane flyovers follow for I-380 to San Bruno, U.S. 101 south to San Jose and U.S. 101 north to San Francisco. 07/11/18
East End Throwback
Button copy signs previously posted at the six-ramp parclo interchange (Exit 5) with SR 82 (El Camino Real). 11/26/04
Following Exit 6A to the separation for U.S. 101 south and the passenger terminal flyover ramps. 11/26/04
West End – San Bruno, California
West at 
Interstate 380 west ahead of the directional T interchange (Exit 5) with I-280 (Father Junipero Serra Freeway). 07/15/23
The exchange with I-280 includes provisions for the planned extension of I-380 west to SR 1. A separate proposal considered extending I-380 west to nearby SR 35 (Skyline Drive). 07/15/23
The I-380 mainline defaults onto I-280 north with three lanes as Exit 5 A. Left Exit 5 B comprises a flyover onto I-280 south toward San Jose. 07/15/23
South at
Southbound Interstate 280 ahead of Exit 43 A for I-380 east to San Francisco International Airport (SFO). Exit 43 B, 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. 07/11/18
An auxiliary lane accompanies I-280 south from Avalon Drive to the back to back ramps at Exit 43 B for Sneath Lane and Exit 43 A for Interstate 380 east. 07/11/18
Interstate 380 leads directly to San Francisco International Airport (SFO) from I-280. I-380 is also the lone freeway linking I-280 with U.S. 101 between San Francisco and San Mateo. 07/11/18
Taking Exit 43 A, a two lane ramp links I-280 south with I-380 east below an abandoned overpass built for the western extension. 07/11/18
East End Throwback
Button copy signs for Interstate 280 were replaced by 2008 to display Exits 5B/A. 11/26/04
Replaced button copy sign for I-380 and U.S. 101 at the Avalon Drive under crossing. 11/26/04
Page updated September 7, 2023.