Interstate 5 spans the West Coast, originating at the nation’s busiest international border crossing at San Ysidro (San Diego), California, and culminating at Blaine, Washington. This freeway connects all of the major population centers of the western seaboard, including San Diego, Los Angeles, Sacramento, Portland and Seattle. Via Interstates 580 and 505, Interstate 5 provides freeway connections to the populous San Francisco Bay Area.
Guide and Major Projects
Beginning at the International Border at San Ysidro, Interstate 5 connects the metropolitan areas of Tijuana, Baja California, and San Diego, California. Due to significant traffic loads at all hours of the day and night, plans called for expansion of the northbound border inspection facility and realignment of the southbound lanes into a larger border inspection facility. A three phase, $735-million project expands the port of entry to 62 northbound inspection booths and one dedicated bus lane among other improvements including expanded pedestrian processing facilities and connectivity to a new multi-modal transportation hub in Mexico. Initial work was completed in April 2011 when a new pedestrian bridge was completed. Phase 2, pertaining to the I-5 North and Southbound Inspection Facilities, is slated for completion in summer 2018.3
Passing through the border inspection station, Interstate 5 immediately assumes the role of an urban freeway, with eight to twelve lanes for its entire length through San Diego County. The freeway replaces old U.S. 101, which used to follow surface streets between the border and Downtown San Diego. While some parts of the old road are buried (such as in National City, where it was overrun by the Mile of Cars and in La Jolla, where Interstate 5 was routed on top of the old road), many extant sections of U.S. 101 are still around for driving enjoyment, especially between La Jolla and Oceanside via San Diego County Route S-21.
With the recent population explosion resonating throughout Southern California, eight-lane Interstate 5 is ill-equipped to handle the needs of daily commuters, visitors, business people, international tourists, truckers and more. Plans call for expansion of Interstate 5 in San Diego, for instance, to ten or more lanes, including the implementation of high occupancy vehicle lanes. One such project will add an HOV lane per direction from Manchester Avenue to California 78 during work between late 2015 and 2018 (see this document for details). This work precedes the planned construction of I-5 Express Lanes, from La Jolla Village Drive in San Diego to Harbor Drive in Oceanside. These will operate similarly to the I-15 Express Lanes through San Diego County. Work proposed between 2020 and 2035 will upgrade the existing carpool lanes to Express Lanes.
One such large-scale project was the reconstruction and expansion of the interchange between Interstate 5 and Interstate 805 through the San Diego communities of Sorrento Valley (Mira Mesa), Torrey Hills and Carmel Valley. The freeway was widened to a dual freeway configuration, which allows for trucks and local traffic to use the lanes that lead to exit ramps, while through traffic may use the express lanes. The northbound local bypass opened in early 2006, followed by the southbound local bypass in spring 2007.
Continuing north through Orange County, Interstate 5 was reconstructed and widened substantially in the mid-2000s between California 73 and California 91. Parts of this section of freeway contain as many as 22 lanes, including auxiliary and carpool lanes. Even so, the interchange between Interstate 5 and Interstate 405 can be very busy and congested during rush hour periods and on weekends.
Entering Los Angeles County, Interstate 5 reverts to its originally constructed alignment, following concrete poured in the 1960s in some areas. Interstate 5 is generally six lanes wide. Construction underway expands the freeway northwest from Buena Park to Commerce. Work started between the Coyote Creek over crossing and Marquart Avenue in January 2012. Construction continues on Segment A through December 2018. Segment B between I-605 and I-710 and C at the I-710 interchange is proposed to start in winter 2025. For more, please see the official web page.
One of the biggest congestion points along Interstate 5 is at its junction with Interstate 10, U.S. 101 and California 60. This maze of interchanges, ramps and other maneuvers remains largely unchanged since its original construction, and so it is overwhelmed by traffic every day. Through traffic on Interstate 5 is squeezed into two lanes at one point as well as merged with traffic from the busiest freeway in Southern California, Interstate 10 (the Santa Monica Freeway). From here, Interstate 5 generally follows old U.S. 99, which was decommissioned in 1964.
Leaving the Los Angeles Basin, Interstate 5 regains its full freeway configuration of eight to ten lanes, but the evening commute generally hits at the north end of San Fernando Valley. The interchange between Interstate 5, Interstate 210 and California 14 is a choke point, even with the truck bypass. The California 14/I-5 interchange is also the site of two devastating earthquake collapses, one in 1971’s Sylmar Earthquake and the other in 1994’s Northridge Earthquake.
Beyond San Fernando Valley, Interstate 5 ascends to one of the highest points along its journey along the western coast. Crossing the Tehachapi Mountains at Tejon Pass (elevation 4,144 feet) as well as the infamous San Andreas fault, I-5 transitions from an urban to a rural freeway for the first time in its northbound journey. In order to make the grade manageable for trucks, the northbound lanes of Interstate 5 just north of Castaic switches sides with the southbound lanes. The result is several miles in which northbound Interstate 5 is on the left side of the freeway rather than the right side! This kind of configuration is rare; Interstate 8 east of Yuma, Arizona has a similar inversion of its east and westbound lanes.
Descending into the massive Central Valley via the Grapevine, Interstate 5 immediately splits into two routes: I-5 follows the Westside Highway, avoiding all major population centers between the Grapevine and Tracy. California 99 follows the old U.S. 99 route, connecting with most major Central Valley cities, including Bakersfield, Fresno, Modesto, and Stockton. Fresno holds the dubious distinction as the largest city in the country not served by an Interstate highway. Nevertheless, Fresno still has its old standby, California 99. Most traffic destined for the Bay Area and points northward prefer to take Interstate 5, which is shorter and avoids urban traffic.
The next several hundred miles can be peaceful or stressful depending on the day of the week and time of year. During holiday weekends, Interstate 5 can be a parking lot filled with travelers eager to reach relatives and friends in Northern or Southern California. At other times, Interstate 5 is as free-flowing as any rural freeway. However, over the past decade or so, more people have been using “the 5” to connect between Southern and Northern California. As this kind of usage increases, more traffic delays become problematic in the Central Valley, even if the nearest city is many miles away.
Once at Interstate 580, travelers en route to the San Francisco Bay Area may exit west to their destination. Interstate 5 remains in the Central Valley, closely following the California Aqueduct and Path 22, the flagship transmission power lines that follow the freeway through much of the state. Whenever Southern California needs power from Northern California, these power lines carry that extra power needed to satisfy their needs. The power lines also work in reverse, thus ensuring that neither part of the state is without power for a long period of time.
Finally Interstate 5 passes through some cities in the Central Valley, including Tracy, Manteca, Stockton, and the capital city, Sacramento. By the time Interstate 5 reaches Sacramento, it has expanded to eight to ten lanes. Passing under Business Loop I-80, I-5 is well below grade … so low that the bottom of the nearby Sacramento River is higher than the level of the freeway as it passes by Old Town Sacramento. Occasionally, with significant amounts of rain and other variables, this section of Interstate 5 may flood.
However, there are plans to change this. Some Sacramento leaders want to see their access to the river restored, and part of that would require removing Interstate 5 from between downtown Sacramento and Old Town Sacramento. I-5 would then be re-routed to the west, connecting with Interstate 80 and Business Loop I-80 in West Sacramento at their current interchange, then continuing northeast to rejoin current I-5 at the current I-5/I-80 interchange. This ambitious plan faces many hurdles, including major cost and environmental concerns, and nothing has been finalized.
Interstate 5 leaves Sacramento almost as quickly as it arrived. Again meeting California 99, I-5 serves the west edge of the northern Central Valley (via old U.S. 99W), while California 99 and California 70 serve the east side of the valley (via old U.S. 99E and Alternate U.S. 40). Most of the towns passed by Interstate 5 are tiny, but they have seen growth through the addition of fast food restaurants, gas stations and motels. Behind the veneer of these services, old towns with a great deal of history and farming tradition — such as Williams, Arbuckle, Willows, and Orland — await.
Passing through Red Bluff, Interstate 5 enters the rolling hills that separates Red Bluff from Redding. I-5 leaves the Central Valley, and glimpses of towering Mount Shasta become common. Changing from the great valley to mountain scenery, I-5 cuts towering mountains as it winds its way northward along old U.S. 99. This terrain remains similar as Interstate 5 passes through northern California and enters southern Oregon. By the time it reaches Eugene, the freeway has entered the narrow Willamette Valley, and it approaches Portland.
Both Portland and Seattle have several concerns with Interstate 5. In Portland, the Interstate Bridge over the Columbia River is substandard and causes traffic delays daily. In Seattle, the freeway is congested daily and cannot support the ever increasing crush of traffic.
High Priority Corridor
Interstate 5 is part of High Priority Corridor 30: Camino Real for its entire length. In the Everett-Seattle-Tacoma area, Interstate 5 is also part of High Priority Corridor 35: FAST Corridor.
Parallel U.S. Routes
South of San Diego, Interstate 5 replaced U.S. 101, thus truncating that route in Los Angeles. However, for the rest of its journey northward, Interstate 5 roughly parallels and replaces former U.S. 99, which was decommissioned in stages between 1964 and 1972. Remnants of the old route are now part of California 99, Oregon 99, and Washington 99. Although Interstate 5 runs closely to the original route of U.S. 99, large sections of the freeway avoid the old alignment and take on a new alignment, especially between Wheeler Ridge and Manteca. Old U.S. 99 instead passed through Bakersfield, Fresno, and Modesto via modern California 99, while Interstate 5 stays clear of urban areas until reaching Stockton. In addition, Interstate 5 replaced U.S. 99W between Woodland and Red Bluff. Today Interstate 5 only intersects a handful of U.S. routes, and only three of them are in California (U.S. 101, U.S. 50, and U.S. 97).
North End – International Border – Blaine, WA
South End – International Border – San Diego, CA
Branch Routes – 13
Total Mileage – 1,381.29
California – 796.53 miles
Cities – San Diego, Santa Ana, Los Angeles, Stockton, Sacramento, Red Bluff, Anderson, Redding, Yreka
- Junctions –
Oregon – 308.14 miles
Cities – Ashland, Medford, Grants Pass, Roseburg, Eugene, Salem, Portland
- Junctions –
Washington – 276.62 miles
Cities – Vancouver, Kelso, Chehalis, Centralia, Olympia, Tacoma, Seattle, Everett, Mt. Vernon, Bellingham
- Junctions –
Source: December 31, 2017 Interstate Route Log and Finders List
I-5 Annual Average Daily Traffic (AADT)
|Location||Vehicles per day|
|San Diego, CA||262,000|
|Lake Forest, CA||356,000|
|Santa Ana, CA||314,000|
|Los Angeles, CA||291,000|
|Paicoma (Los Angeles), CA||302,000|
|Red Bluff, CA||31,500|
|Siskiyou Summit, OR||15,000|
|Eugene / Springfield, OR||68,600|
Source: Caltrans, Traffic Operations Program – Traffic and Vehicle Data Systems 
2002 Traffic Volumes (ODOT)
2002 Annual Traffic Report (WSDOT)
* – estimate 240,000 mainline and 54,000 reversible lanes
Ramp meters for Interstate 5 are also used in San Diego, Los Angeles, Sacramento, and Seattle.
The initial stretch of Interstate 5 built in the Seattle-Tacoma area bypassed U.S. 99 from 54th Avenue East at Fife to Washington 18 near Kitts Corner.
The northern section of I-5 through Los Angeles was completed in 1963 between Lankershim Boulevard (Exit 152) and Interstate 210 (Exits 161A/B).
Sections of Interstate 5 in Southern California were constructed prior to the passage of the Federal Highway Act of 1956, including the Aliso Street Viaduct (built in 1948), portions of former U.S. 101/Santa Ana Freeway (south of Los Angeles) and portions of U.S. 101/Montgomery Freeway (south of San Diego). These sections were added to Interstate 5, and U.S. 101 was decommissioned on shared alignments in 1964. Much of the Ridge Route replacement between Los Angeles and the Central Valley over Tejon Pass and the Grapevine (approximately 43 miles) was completely opened by 1970; improvements included construction of separate alignments for each direction of traffic. Near Castaic, the northbound lanes cross under the southbound lanes to allow for a better uphill grade; they switch back near the Templin Highway (Old U.S. 99/Ridge Route Alternate) interchange. A major freeway corridor built with Federal Highway Act funds was the Westside Highway. Construction on this 321-mile long freeway began in 1963. The last section of Interstate 5/Westside Highway to be completed in California located near Stockton, which opened to traffic on October 12, 1979.2
Interstate 5 in Oregon was completed and open to traffic as a four-lane highway by October 1966. Two segments were completed at that time to finish the route in Oregon: (1) the Marquam Bridge over the Willamette River in Portland (between the Baldock Expressway and East Bank Freeway) opened on October 18, 1966, and (2) a segment south of Canyonville near Douglas County was opened second, on October 22, 1966. The new freeway was dedicated in a ceremony held at the Cow Creek Rest Area.1
Interstate 5 was originally programmed to have one split route: Interstate 5W. Interstate 5W was to start near Vernalis, follow Interstate 580 to Oakland via Hayward, then return to Interstate 5 via Interstate 80 and Interstate 505 near Vacaville. A few shields were minted and posted, but the designation was eliminated in favor of Interstates 505 and 580.
North End – International Border – Blaine, Washington
British Columbia 99 north
Peace Arch State Park at
D Street west at
South End – International Border – San Diego (San Ysidro), California
- Interstate 50th Anniversary: The Story of Oregon’s Interstates by the Oregon Department of Transportation, as compiled from a 2004 report entitled “The Interstate Highway System in Oregon, An Historic Overview” by George Kramer.
- California Celebrates 50 Years of the Interstate Highway System by Caltrans (California Department of Transportation).
- San Ysidro LPOE Project Facts, U.S. General Services Administration web site.
Page updated July 7, 2015.