Interstate 405 - Definition and Overview

Interstate 405 is the designation of three different tertiary interstate routes of Interstate 5.

California

Interstate 405 in southern California, part of the San Diego Freeway for its entire length, is a loop branch of Interstate 5. It splits off from I-5 in the northern San Fernando Valley, travels south through the Santa Monica Mountains, and generally mirrors the path of the Pacific coast thereafter (albeit 5-10 miles inland). It rejoins I-5 at the El Toro Y, a notorious traffic congestion point, near the former El Toro Marine Corps airbase in central Orange County.

Detailed information on I-405, including cities through which it passes and freeways with which it intersects, can be found on the San Diego Freeway page.

Washington

Interstate 405 in Washington state is a 30-mile loop route that bypasses downtown Seattle east of Lake Washington. The northern terminus is in Alderwood, Washington and the southern terminus is in Tukwila. The highway runs through what has since become the "Eastside" technology center of Redmond, Bellevue, and Kirkland, making it an often congested commuter path. I-405 is known for its meandering "s-curves" through Renton. It intersects with Interstate 90 and a number of major state routes. Its official name is "Renton Freeway," though it is not signed as this. Interstate 405 was laied overtop of historic Secondary State Highway 2A.

Major Interchanges

• Interstate 5 (terminii in Tukwila and Lynnwood)
• Washington State Route 167 (exit 2 in Renton)
• Interstate 90 (exit 11 in Bellevue)
• Washington State Route 520 (exit 14 in Bellevue)
• Washington State Route 522 (exit 23 in Bothell)
• Washington State Route 527 (exit 26 in Mill Creek, Washington)
• Washington State Route 900 (exit 5 in Renton)
• Washington State Route 518 (continuation beyond Tukwila)
• Washington State Route 525 (continuation beyond Lynnwood)

Major cities and suburbs

• Lynnwood
• Bothell
• Kirkland
• Bellevue
• Newcastle
• Renton
• Tukwila

Oregon

Interstate 405 in Oregon is a short loop route, also known as the Stadium Freeway, that connects downtown Portland west of the Willamette River to Interstate 5. I-405 only travels through the city of Portland. It opened to traffic on Feb. 25, 1969. It contains an interchange intended for the cancelled I-505.

On its northern end, I-405 crosses the Willamette River on the Fremont Bridge. See Interstate 5.

Interstate 405 shares pavement with U.S. Highway 30 from Exit 0 (Interstate 5) to Exit 1A (NW Industrial District). It intersects with U.S. Highway 26 at Exit 1D.