Interstate 405 is a 72-mile auxiliary route of I-5 through the western Los Angeles Basin and Orange County, running from Irvine in the south to San Fernando in the north. Despite its modest length, it carries some of the highest traffic volumes of any urban interstate in the United States — the Sepulveda Pass segment between West LA and the San Fernando Valley regularly handles over 380,000 vehicles per day, making it among the busiest single segments of any US interstate.
For freight, I-405 is the bypass alternative to I-5 through downtown Los Angeles. Container traffic to and from the Port of Long Beach uses both I-405 and I-710, and the Long Beach-to-LAX corridor is one of the most truck-dense urban segments in the country. The route serves LAX directly and connects to virtually every major LA-area freeway: I-105, I-10, I-110, US-101, and I-5 itself at both endpoints.
There is no significant terrain — I-405 is an entirely urban interstate, climbing only over Sepulveda Pass at about 1,170 ft. The dominant operational issues are chronic congestion (peak periods often exceed 4-hour windows), weather-related disruptions are limited to occasional brush fires that close lanes for smoke, and seasonal Santa Ana wind events that affect the Sepulveda Pass.
- Auxiliary route of I-5 through the western LA Basin and Orange County
- 72 miles total — one of the shortest interstates with heaviest peak volumes
- Sepulveda Pass segment carries over 380,000 vehicles per day
- Direct connection to LAX (Century Boulevard exit)
- Concurrent with no other interstate
- Tolled HOT lanes (Express Lanes) operate in Orange and LA counties
- CARB-compliant truck routing applies — pre-2010 trucks restricted