Interstate 5 (I-5) is a major north–south route of the Interstate Highway System in the United States, running largely parallel to the Pacific Coast between the Mexican border and the Canadian border. The segment of I-5 in California runs across the length of the state from the Mexican border at the San Ysidro Port of Entry in the San Ysidro neighborhood of San Diego to the Oregon state line south of the Medford-Ashland metropolitan area. It is the longest interstate in California at , and accounts for more than half of I-5's total length of . It is also the second longest stretch of Interstate Highway (and the longest for a north-south Interstate) with a single designation within a single state after I-10 in Texas.
It is the most-used of the two major north–south routes on the Pacific Coast, the other being U.S. Route 101 (US 101), which is primarily coastal. I-5 links the major California cities of San Diego, Santa Ana, Los Angeles, Stockton, Sacramento, and Redding. The San Francisco Bay Area is about west of the highway.
I-5 is known colloquially as "the 5" to Southern California residents and "5" to Northern California residents due to variations in California English. I-5 also has several named portions: the John J. Montgomery Freeway, San Diego Freeway, Santa Ana Freeway, Golden State Freeway, and West Side Freeway.
Route description
The entirety of Interstate 5 in California is defined in section 305 of the California Streets and Highways Code as Route 5:Route 5 is from the international boundary near Tijuana to the Oregon state line via National City, San Diego, Los Angeles, the westerly side of the San Joaquin Valley, Sacramento, and Yreka; also passing near Santa Ana, Glendale, Woodland, and Red Bluff.
This definition corresponds with the Federal Highway Administration (FHWA)'s route logs of I-5.
I-5 is part of the California Freeway and Expressway System, and is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. The segment of I-5 from State Route 89 (SR 89) to US 97 forms part of the Volcanic Legacy Scenic Byway, an All-American Road. I-5 is also eligible to be included in the State Scenic Highway System; however, it is a scenic highway as designated by the California Department of Transportation (Caltrans) only from SR 152 to I-580.
San Diego County I-5 begins at the San Ysidro Port of Entry from Mexico in the San Ysidro neighborhood of San Diego. Immediately after the border, I-805 splits off to the northeast and serves as a bypass of I-5 that avoids downtown San Diego. I-5 itself continues northwest and meets the western end of SR 905, a route that connects with the Otay Mesa border crossing. I-5 then continues northward and joins the southern end of SR 75, a highway connecting to Coronado via the Silver Strand. I-5 then enters Chula Vista, briefly leaving the San Diego city limits. It continues along the east side of San Diego Bay where it intersects with SR 54 and enters National City. From there, I-5 veers around Naval Base San Diego and reenters the city limits of San Diego. I-5 subsequently intersects with four state routes: the southern end of SR 15, which continues the I-15 corridor, SR 75 and the Coronado Bridge, the western end of SR 94, and SR 163. In addition to serving downtown San Diego, I-5 also provides access to Balboa Park from the Pershing Drive exit. The portion of I-5 from the Mexican border to SR 94 at downtown San Diego is named the John J. Montgomery Freeway in honor of John J. Montgomery, a pioneer aviator who flew a glider from a location near Chula Vista in 1884.
I-5 continues northwest from downtown as the San Diego Freeway until it reaches its junction with I-8, then turns slightly to the north while passing SeaWorld and Mission Bay. Thereafter, I-5 intersects the western end of SR 52 near La Jolla before entering University City. At Nobel Drive, the San Diego LDS Temple towers over I-5. Shortly afterward, I‑5 passes through the UC San Diego campus and intersects the northern terminus of I-805 before continuing north and intersecting the western end of SR 56. At this interchange, there is a local bypass that provides the only access to Carmel Mountain Road from both directions and provides the only direct access to SR 56 going northbound.
North of the San Diego city limits, I-5 enters the city limits of Solana Beach, and then three incorporated cities to the north: Encinitas, Carlsbad and Oceanside. In Oceanside, I-5 intersects the SR 78 freeway and the SR 76 expressway and continues through Camp Pendleton. It then follows the Pacific Ocean coastline for the next . Toward the northern end of its routing through Camp Pendleton, I-5 passes through San Onofre State Beach and near the San Onofre Nuclear Generating Station. I-5 enters Orange County at the Cristianitos Road exit.
Orange County
Upon entering Orange County, I-5 goes through San Clemente. At Dana Point, I-5 turns inland while SR 1 continues along the coast. I-5 then heads due north through San Juan Capistrano and Mission Viejo, intersecting the SR 73 toll road heading northwest. I-5 continues to the El Toro Y interchange with I-405 in southeastern Irvine, splitting into lanes for regular traffic as well as for truck traffic (though autos can use these lanes as well). From that point, I-405 takes over the San Diego Freeway designation, while I-5 becomes the Santa Ana Freeway as it runs southeast to northwest.
After the El Toro Y junction, I-5 intersects SR 133, a toll road that eventually connects to SR 241. Just before the Tustin city limits, I-5 passes over SR 261, the final toll road of the Eastern Transportation Corridor, but traffic must use Jamboree Road to access the latter. I-5 then intersects SR 55 and enters Santa Ana, the county seat of Orange County. Towards the northern side of Santa Ana, I-5 intersects both SR 57 and SR 22 in what is known as the Orange Crush interchange. Following this, I-5 briefly enters the city of Orange and then traverses Anaheim, passing along the north side of Disneyland. I-5 then intersects SR 91, passes through Buena Park and crosses into Los Angeles County.
Los Angeles County After crossing the county line, I-5 goes through several cities southeast of Los Angeles, including La Mirada, Santa Fe Springs, and Norwalk. In Downey, I-5 intersects I-605, which serves as a north–south connector route between the cities east of Los Angeles, including those in the San Gabriel Valley. I-5 then enters Commerce, passing the Citadel Outlets shopping center, and intersects I-710 before entering the large unincorporated community of East Los Angeles and later the city proper of Los Angeles. When the freeway reaches the East Los Angeles Interchange east of downtown Los Angeles, I-5 becomes the Golden State Freeway as US 101 takes over the Santa Ana Freeway designation. At this interchange, I-10, SR 60, and US 101 intersect; I-10 continues north on I-5 for about before continuing east towards San Bernardino and points farther east.
On the north side of downtown, the Golden State Freeway follows the Los Angeles River, intersects SR 110 and SR 2 and passes along the eastern side of Griffith Park. The route continues through the San Fernando Valley, intersecting the Ventura Freeway (SR 134). It briefly enters the city of Glendale and then Burbank, passing near Burbank Airport before reentering the Los Angeles city limits and intersecting the northern end of the Hollywood Freeway (SR 170). Near the city of San Fernando, I-5 intersects SR 118. Following this, I-5 intersects three routes in succession: the northern end of I-405, the western end of I-210, and the southern end of SR 14 at the Newhall Pass interchange. It then crosses the Newhall Pass through the Santa Susana Mountains into the Santa Clarita Valley. I-5's carpool lanes also have direct connectors with the carpool lanes on the SR 170 and SR 14 freeways (an additional direct connector with the HOV lanes on I-405 near Mission Hills is planned). This allows a continuous HOV lane to run from Palmdale to North Hollywood via SR 14 to I-5 to SR 170.
I-5 continues along the western city limits of Santa Clarita and passes Six Flags Magic Mountain, intersecting SR 126 just north of there.
Tejon Pass and Grapevine
The Golden State Freeway then rises sharply, passing by Lake Castaic and undergoing a unique crossover resulting in a left-driving configuration for about before the highway crosses back into its standard alignment. This section is known as the Five Mile Grade. After cresting the Five Mile Grade, the freeway enters the Angeles National Forest. It passes Pyramid Lake and intersects SR 138 before crossing the Tejon Pass through the Tehachapi Mountains near the Los Angeles–Kern county line, with Path 26 power lines generally paralleling the freeway.
After entering Kern County, the freeway sharply descends for from at the Tejon Pass to at Grapevine near the southernmost point of the San Joaquin Valley, approximately south of Bakersfield and south of its interchange with SR 99 at Wheeler Ridge.
This stretch of I-5 through the Tejon Pass and Grapevine typically gets snow at higher elevations during the winter. Although Caltrans may require vehicles to use snow tires, snow chains, or other traction devices during and after snowstorms, the California Highway Patrol will instead usually close this segment altogether during these conditions because of the steep grade of the pass, and the amount of passenger traffic and big-rigs that generally use the corridor. Whenever there is such a closure, traffic must either wait for it to reopen, or endure a multi-hour detour. An automated gate on the freeway's median in Castaic north of Lake Hughes Road allows drivers to turn around when such closures occur.
Central Valley From SR 99 at Wheeler Ridge to Woodland, I-5 is known as the West Side Freeway. I-5 parallels SR 33, skirting along the far more remote western edge of the Central Valley, and is largely removed from the major population centers such as Bakersfield, Fresno and Modesto; other state highways provide connections. I-5 still runs within the vicinity of Avenal, Coalinga, Los Banos, and a handful of other smaller cities on the western edge of the Central Valley. For most of this section, the Path 15 electrical transmission corridor follows the highway, forming an infrastructure corridor along with the California Aqueduct. After the Grapevine, I-5 crosses the California Aqueduct. This is first time out of 5 times that I-5 crosses the aqueduct.
North of the Grapevine, I-5 intersects SR 166, SR 119 and SR 43 before meeting SR 58, a highway that continues east to Bakersfield, near the town of Buttonwillow. I-5 then intersects SR 46 before entering Kings County. From the Utica Avenue exit to I-580, I-5 parallels the eastern foothills of the Diablo Range. It crosses the California Aqueduct for the second time. In Kings County, I-5 intersects SR 41 before briefly entering the city limits of Avenal, where it intersects SR 269. In Fresno County, I-5 intersects SR 198 and SR 145 before running concurrently with SR 33 for several miles. I-5 then crosses into Merced County, intersecting SR 165, SR 152 and SR 33 near the San Luis Reservoir (where SR 152 provides a major connection to the Monterey Peninsula and the Silicon Valley), and SR 140 at the Stanislaus county line. I-5 crosses the California Aqueduct for the third time between SR 152 and SR 33 and again near Crows Landing.