Interstates 405, in accordance with the Interstate naming rules
, are bypass
loops off of the "parent" Interstate 5
freeway. One Interstate 405 is found in each of the states that Interstate 5 passes through, Washington
, and California
- Interstate 405 in Washington is found in the Seattle area. This approximately 30-mile loop begins off of I-5 in the northern Seattle suburb of Lynnwood and continues south, passing through Bothell, Kirkland, Bellevue, Renton, and Tukwila, before ending back into I-5. Along the way, it intersects Interstate 90, and Washington State routes 522, 520, and 167. I-405 is the main north-south corridor on the eastern shores of Lake Washington.
- Interstate 405 in Oregon is found in the Portland area. This freeway is almost miniature, forming an approximately 4-mile-long loop around the downtown core of the city. The freeway diverges from I-5 in an industrial district north of the Rose Quarter and crosses the Fremont Bridge into downtown, curls south around the center in a trench the width of a city block, and ends into I-5 at the northern end of the John's Landing neighborhood. Along the way it connects into US-26 and US-30.
- Interstate 405 in California is found in the Los Angeles area. This freeway loop is about 70 miles long. It begins off of I-5 in the San Fernando Valley, just next to the tiny municipality of San Fernando. It continues south through Beverly Hills, Culver City, Inglewood, and El Segundo. In Lawndale and Torrance it arcs to a southeasterly direction, and then continues through Carson, Long Beach, Signal Hill, Rossmoor, Westminster, Midway City, Huntington Beach, Fountain Valley, Costa Mesa, and Irvine. In eastern Irvine, I-405 rejoins its parent. Along the way it connects with US-101, Interstate 10, Interstate 105, Interstate 110, Interstate 710, and Interstate 605. I-405 in the LA area is known as the "San Diego Freeway"; I-5 south of Irvine then takes over this moniker, and retains it all the way to San Diego.