Back Interstate 5 ve Washingtonu Czech Interstate 5 em Washington Portuguese Міжштатна автомагістраль 5 у Вашингтоні Ukrainian 5号州际公路华盛顿州段 Chinese
 Interstate 5 | ||||
|---|---|---|---|---|
| Purple Heart Trail | ||||
 A map of Western Washington with I-5 highlighted in red | ||||
| Route information | ||||
| Maintained by WSDOT | ||||
| Length | 276.62 mi[1][2] (445.18 km) | |||
| Existed | August 14, 1957[3][4]–present | |||
| History | Completed in 1969[5] | |||
| Tourist routes | ||||
| NHS | Entire route | |||
| Major junctions | ||||
| South end |  I-5 at the Oregon state line in Vancouver | |||
| North end |  Highway 99 at the Canadian border in Blaine | |||
| Location | ||||
| Country | United States | |||
| State | Washington | |||
| Counties | Clark, Cowlitz, Lewis, Thurston, Pierce, King, Snohomish, Skagit, Whatcom | |||
| Highway system | ||||
| ||||
Interstate 5 (I-5) is an Interstate Highway on the West Coast of the United States that serves as the region's primary north–south route. It spans 277 miles (446 km) across the state of Washington, from the Oregon state border at Vancouver, through the Puget Sound region, to the Canadian border at Blaine. Within the Seattle metropolitan area, the freeway connects the cities of Tacoma, Seattle, and Everett.
I-5 is the only interstate to traverse the whole state from north to south and is Washington's busiest highway, with an average of 274,000 vehicles traveling on it through Downtown Seattle on a typical day. The segment in Downtown Seattle is also among the widest freeways in the United States, at 13 lanes, and includes a set of express lanes that reverse direction depending on time of the day. Most of the freeway is four lanes in rural areas and six to eight lanes in suburban areas, including a set of high-occupancy vehicle lanes in the latter. I-5 also has three related auxiliary Interstates in the state, I-205, I-405, and I-705, as well as several designated business routes and state routes.
The freeway follows several historic railroads and wagon trails developed during American settlement of western Washington in the mid-to-late 19th century. The state legislature incorporated local roads into the Pacific Highway in 1913, connecting the state's southern and northern borders between Vancouver and Blaine. The Pacific Highway was built and paved over the next decade, and became the northernmost segment of the national U.S. Route 99 (US 99) in 1926.
The federal government endorsed the creation of a national expressway system in the 1940s, including several bypasses on US 99 that were built by the state in the early 1950s. The state's planned toll superhighway in the Seattle area was shelved in favor of a federally-funded freeway under the new Interstate Highway System, under which I-5 was created in 1957. Construction of I-5 was completed in 1969, and several segments of the highway have been widened or improved in the decades since.
- ^ Multimodal Planning Division (February 26, 2014). "State Highway Log Planning Report 2013, SR 2 to SR 971" (PDF). Washington State Department of Transportation. pp. 220–322. Retrieved June 14, 2018.
- ^ "Table 1: Main Routes of the Dwight D. Eisenhower National System Of Interstate and Defense Highways as of December 31, 2017". Federal Highway Administration. December 31, 2017. Retrieved June 15, 2018.
- ^ Official Route Numbering for the National System of Interstate and Defense Highways (Map). American Association of State Highway Officials, Public Roads Administration. August 14, 1957. Retrieved June 14, 2018.
- ^ Weingroff, Richard F. (1996). "Federal-Aid Highway Act of 1956, Creating the Interstate System". Public Roads. 60 (1). Washington, D.C.: Federal Highway Administration. ISSN 0033-3735. Retrieved June 14, 2018.
- ^ Dougherty, Phil (April 10, 2010). "Interstate 5 is completed in Washington state on May 14, 1969". HistoryLink. Retrieved June 14, 2018.