Interstate 8 (I-8): Route, Miles by State, Crashes and Bridges

How long is I-8?

FHWA's Route Log gives I-8 348.82 miles as of January 2026: 170.12 in California and 178.70 in Arizona. I-8 shares no pavement with another Interstate, so none of its miles are booked to a different route, and the crash rates below use those two state figures as they stand.

Other published lengths land within two miles of the Route Log. Wikipedia lists 350.34 miles (171.98 in California, 178.36 in Arizona), and Interstate Guide lists 348.25 (169.92 and 178.33). California accounts for most of the spread, with Wikipedia's state figure 1.86 miles above the Route Log's.

Where I-8 starts and ends

The western end is an at-grade intersection with Sunset Cliffs Boulevard and Nimitz Boulevard in San Diego's Ocean Beach neighborhood. The eastern end is a trumpet interchange with I-10 at I-8 Exit 178 (I-10 Exit 199), on the southeast side of Casa Grande and roughly halfway between Phoenix and Tucson.

Eastbound, I-8 is the Ocean Beach Freeway until it crosses I-5 near Old Town, then the Mission Valley Freeway past Hotel Circle, La Mesa and El Cajon. It climbs through the Cleveland National Forest past Alpine and Pine Valley and crosses four high points of roughly 4,000 feet: Carpenter, Laguna and Crestwood summits and the Tecate Divide. The descent into the desert loses 3,000 feet in 11 miles, with eastbound traffic in In-Ko-Pah Gorge and westbound traffic in Devils Canyon.

At the New River crossing near Drew Road, west of El Centro, the road sits 52 feet below sea level, the lowest point on the Interstate system outside underwater tunnels. Farther east it follows the All-American Canal for about 55 miles, cuts through the Imperial Sand Dunes and comes within half a mile of the Mexican border in eastern Imperial County before crossing the Colorado River into Yuma. In Arizona it passes Telegraph Pass, where the eastbound lanes briefly swap to the left of the westbound lanes, then Wellton, Gila Bend, the Sonoran Desert National Monument and Stanfield.

Interstate junctions along I-8

The list below runs west to east and holds three main Interstates: I-5 and I-15 in San Diego, and I-10 where I-8 ends. At Exit 7 in Mission Valley, I-15 begins and heads north while State Route 15 carries on south. I-805, a three-digit branch of I-5, crosses at Exit 6B, and US 95 at Yuma is the only U.S. highway I-8 meets anywhere on its length.

Fatal crashes on I-8

Crashes on I-8 killed 150 people from 2020 to 2024, about 30 a year. That works out to 8.6 deaths per 100 route miles per year, a bit under the Interstate average of 9.5, and I-8 ranks 26th of 56 routes, counting from the highest rate.

California had 114 deaths and a rate of 13.4, more than three times the Arizona rate of 4.0, even though Arizona has slightly more miles and had 36 deaths. San Diego County led all counties with 72 deaths and Imperial County followed with 42, which together account for every California death. On the Arizona side, Yuma County had 13, Pinal 12 and Maricopa 11.

Deaths held at 37 in both 2020 and 2021, slipped to 32 in 2022, fell to 19 in 2023 and rose to 25 in 2024. NHTSA still treats the 2024 figure as preliminary.

Counties with the most I-8 crash deaths

Bridges on I-8

The 2025 National Bridge Inventory counts 358 bridges on the I-8 main line, 204 in Arizona and 154 in California. Of those, 218 rate Good, 138 Fair and only 2 Poor, both in Arizona, which is about half of one percent. The median bridge was built in 1966.

In the mountains, the Pine Valley Creek Bridge, officially the Nello Irwin Greer Memorial Bridge, is a segmental balanced cantilever span that opened in November 1974 and carries the freeway about 450 feet above the valley floor.

Tolls on I-8

FHWA's toll facility inventory for January 1, 2023 lists nothing on I-8, so a trip from Ocean Beach to Casa Grande carries no toll charges. Neither Wikipedia nor Interstate Guide mentions any toll or express lanes added on the route since then.

How I-8 replaced US 80

I-8 took over most of the old US 80 corridor across California and western Arizona. Wikipedia dates the route to August 14, 1957, the year work began on a US 80 freeway in San Diego between US 395 and Ward Road. Arizona opened its first pieces in 1959, from Sentinel to Piedra and from Gila Bend to State Route 84. Between Gila Bend and Casa Grande the Interstate replaced old State Route 84, since US 80 turned north at Gila Bend toward Buckeye.

California posted I-8 and retired US 80 in its 1964 renumbering. The Ocean Beach Freeway, built as State Route 109, joined I-8 in the early 1970s and pushed the western end past I-5 to Sunset Cliffs Boulevard. California's last gap, between Sunrise Highway and La Posta Road, closed in May 1975. In September 1976 the remains of Tropical Storm Kathleen washed out the road near Ocotillo, and that stretch did not reopen until February 1978.

The Colorado River bridge at Yuma was the last link. Wikipedia gives its opening as September 20, 1978, which completed I-8 from San Diego to Casa Grande; Interstate Guide dates it to 1979. In 1995 the Border Patrol built an interior checkpoint near Buckman Springs Road, just east of Laguna Summit. Officially the California section is the Border Friendship Route, and through San Diego County and into Imperial County it is also signed as the Kumeyaay Highway.

I-8 traffic and road conditions

Searches for I-8 closures come in bursts, rising to several times their normal level in some months. Before you head out, check the California and Arizona traveler sites below for current lane closures, crashes and weather on the stretch you plan to use.

I-8 questions