The entirety of Interstate 10 in California is defined in section 310 of the
California Streets and Highways Code as
Route 10, and that the highway is from: (a) Route 1
State Route 1 (SR 1)] in
Santa Monica to Route 5 [I-5] near Seventh Street in Los Angeles.(b) Route 101
US Route 101 (US 101)] near
Mission Road in Los Angeles to the Arizona state line at the
Colorado River via the vicinity of
Monterey Park,
Pomona,
Colton,
Indio, and
Chiriaco Summit and via
Blythe. Because I-10 west of I-5 cannot access US 101, and I-10 east of I-5 cannot access US 101 southbound, signage instead directs motorists to the continuation of I-10 via I-5 between the
East Los Angeles Interchange and the Santa Monica Freeway. The
Federal Highway Administration (FHWA)'s Interstate Highway route logs, along with most maps, also indicate that I-10 is
cosigned along this segment, 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 FHWA. I-10 is eligible to be included in the
State Scenic Highway System, but it is not officially designated as a scenic highway by Caltrans. The Santa Monica Freeway is I-10 from SR 1 to I-5, as named by the State Highway Commission on April 25, 1957. The section between the
Harbor (I-110) and
San Diego (I-405) freeways is also signed as the Rosa Parks Freeway, after the
African-American civil rights activist. The I-10 freeway is signed as the
Christopher Columbus Transcontinental Highway in Santa Monica. The removal of this designation, however, may result in the eventual removal of this signage. At the East Los Angeles Interchange,
SR 60 diverges east toward
Riverside and
Pomona. I-10 then turns north, running concurrently with
I-5 for approximately . Then, I-10 heads east and merges with the traffic from the spur to US 101 onto the San Bernardino Freeway. While the construction of the
Century Freeway several miles to the south reduced
traffic congestion to a considerable amount by creating an alternate route from downtown to
Los Angeles International Airport, the Santa Monica Freeway is still one of the busiest freeways in the world. All three freeway-to-freeway interchanges along its length are notorious for their congestion and are routinely ranked among the top 10 most congested spots in the US. Due to the high traffic volume,
car accidents are so common that Caltrans has constructed special accident investigation sites separated from the freeway by fences. These enable the
California Highway Patrol to quickly clear accidents from the through traffic lanes, and the fences reduce congestion by preventing
rubbernecking (in which vehicles slow down so their occupants can watch the accident investigation). The Santa Monica Freeway is considered the border between
Downtown and
South Los Angeles. Part of the freeway also skims the
Byzantine-Latino Quarter.
San Bernardino Freeway I-10 heads east from the
East Los Angeles Interchange to
I-710 in
Monterey Park. It then continues through the
San Gabriel Valley suburbs of
Alhambra,
Rosemead,
San Gabriel,
El Monte, and
Baldwin Park before intersecting with
I-605. It then travels through
West Covina, briefly enters
Covina, and then travels up the Kellogg Hill into
San Dimas, where I-10 intersects with
SR 57 (formerly part of
I-210) and
SR 71 at the
Kellogg Interchange. I-10 then heads east through Pomona and
Claremont, leaving Los Angeles County to enter
San Bernardino County. In 2019,
SBCTA planned to add two more interchanges in
Fontana at Beech and Alder Avenues to reduce congestion at the Sierra and Cherry avenue exits.
Riverside County In Riverside County, I-10 goes through
Calimesa before entering
Beaumont and merging with the eastern end of SR 60 (itself formerly the California segment of
US 60). In
Banning, I-10 has a diamond intersection with
SR 243 before passing through
San Gorgonio Pass between the
San Bernardino and
San Jacinto mountains (where the vegetation makes a rapid change between Mediterranean and desert ecology) and entering
Palm Springs. The next of the freeway, between
SR 111 and Dillon Road, was named the
Sonny Bono Memorial Freeway in 2002. ==Express lanes==