Interstate 405 (California)

Interstate 405 (California)

Interstate 405 (I-405, and colloquially referred to as "The 405" or the four-oh-five) is a major north–south Interstate Highway in Southern California. It is a bypass of Interstate 5, running along the western and southern parts of the Greater Los Angeles Area from Irvine in the south to near San Fernando in the north. The entire route is known as the northern segment of the San Diego Freeway.

I-405 is a heavily-traveled thoroughfare by commuters and freight haulers along its entire length and is the busiest and most congested freeway in the United States. The freeway's annual average daily traffic between exits 21 and 22 in Seal Beach reached 374,000 in 2008, making it the highest count in the nation. It has played a crucial role in the development of dozens of cities and suburbs along its route through the Greater Los Angeles area.

This route is part of the California Freeway and Expressway System.