Washington State Route 525

SR 525 and its holding lanes at the former Mukilteo ferry terminal

SR 525 begins at the Swamp Creek Interchange with I-5, also serving as the northern terminus of I-405, located in Lynnwood in southern Snohomish County.[3][4] The four-lane controlled-access freeway travels north past Alderwood Mall and a partial cloverleaf interchange with Alderwood Mall Parkway, which serves the eponymous mall.[5] SR 525 continues north under overpasses carrying 164th Street and 148th Street before reaching its partial cloverleaf interchange with SR 99, where the freeway ends.[6] The highway becomes the four-lane Mukilteo Speedway and travels northwest into the city of Mukilteo, serving its commercial and industrial areas located south of Paine Field. SR 525 intersects its spur route, which travels north as Paine Field Boulevard towards the Boeing Everett Factory, before it serves as the western terminus of SR 526. The highway gains a ferry holding lane on its northbound shoulder as it approaches the Mukilteo ferry terminal, located near the Mukilteo Lighthouse Park and a train station, where the designation of SR 525 is carried onto the Whidbey Island Ferry across Possession Sound.[7]

The Mukilteo–Clinton ferry, operated by Washington State Ferries (WSF), takes approximately 20 minutes for each of its 39 daily round-trip crossings.[8] As of October 2017, WSF charges a fare of $5.05 per walk-on passenger and $8.95 per vehicle during off-peak seasons, with varying fares depending on passenger age and vehicle size.[9] SR 525 leaves the ferry terminal at Clinton and travels west through the interior of Whidbey Island in unincorporated Island County as part of the Whidbey Island Scenic Byway, a state scenic byway.[10][11] The highway turns north along Holmes Harbor in Freeland and continues through Greenbank before SR 525 terminates at SR 20 south of Coupeville and the Naval Outlying Landing Field Coupeville.[12][13]

Every year, the Washington State Department of Transportation (WSDOT) conducts a series of surveys on its highways in the state to measure traffic volume. This is expressed in terms of average annual daily traffic (AADT), which is a measure of traffic volume for any average day of the year. In 2012, WSDOT calculated that the busiest section of SR 525 was its southern terminus at I-5 and I-405, serving 61,000 vehicles, while the least busiest section of the highway was at the Mukilteo ferry terminal, serving 5,700 vehicles.[14] SR 525 is designated as part of the National Highway System from Lynnwood to the Mukilteo ferry terminal,[15] classifying it as important to the national economy, defense, and mobility.[16] WSDOT designates the entire route of SR 525 as a Highway of Statewide Significance,[17] which includes highways that connect major communities in the state of Washington.[18]

The Swamp Creek Interchange in Lynnwood, the southern terminus of SR 525 and the northern terminus of I-405, viewed from above in 1967. The overpass in the distance is 164th St. SW, where SR 525 was designated at that time.

SR 525 uses the Whidbey Island Ferry between Mukilteo and Clinton, which began as a route of the Island Transportation Company in 1919. The ferry was later taken over by the Puget Sound Navigation Company, who were sold to the state of Washington in 1951 during the formation of the WSF.[19][20][21] The discontinuous road sections of SR 525 were added to the state highway system in 1937 as SSH 1D and SSH 1I, both branches of PSH 1.[22] SSH 1D traveled 54.73 miles (88.08 km) on Whidbey and Fidalgo islands from the Clinton ferry dock to an intersection with the Anacortes branch of PSH 1 at Sharps Corner.[23][24] SSH 1I traveled 10.63 miles (17.11 km) in a circular arc from Everett to Lynnwood, traveling on Mukilteo Boulevard and the Mukilteo Speedway.[23][24]

SR 525 was established during the 1964 state highway renumbering and codified in 1970 as the successor to both SSH 1D and SSH 1I.[2][25] The 62.04-mile (99.84 km) highway was extended south and east from Highway 99 to the newly-completed I-5 in February 1965, using 164th Street NE until a new freeway could be constructed.[26][27] The highway was truncated from Anacortes to its present terminus south of Coupeville after SR 20 was extended across the state on the North Cascades Highway in 1973.[2] SR 525 was re-aligned onto a two-lane freeway between SR 99 and the Swamp Creek in the 1980s, extending the route to I-405. The Swamp Creek Interchange itself was completed in November 1984.[28]

WSF ferry routes were added to its respective state highways in 1994,[2] eliminating one of two gaps along the route of SR 525, the other being a concurrency with SR 99 that was replaced by a partial cloverleaf interchange in 2000 during the widening of the freeway segment in Lynnwood.[29] A spur route, located completely in Mukilteo, was added to SR 525 in 2001 along the route of the four-lane Paine Field Boulevard, connecting the main highway to SR 526.[2]

The Mukilteo ferry terminal, originally completed in 1957, was replaced by a new facility that opened on December 29, 2020.[30] The new terminal, which includes a waiting area, longer car queues, and a transit center, cost $187 million to construct.[31]

State Route 525 Spur
Location	Mukilteo, Washington
Length	0.86 mi[1] (1.38 km)
Existed	2001–present[2]

SR 525 has a 0.86-mile-long (1.38 km) spur route on Paine Field Boulevard in Mukilteo that connects the northbound lanes of the Mukilteo Speedway to SR 526 eastbound towards Everett and the local Boeing factory.[1] Paine Field Boulevard was built in 1999 and signed as SR 525 Spur in 2001,[2] subsequently being widened and improved in 2003 by WSDOT. A proposal to extend Paine Field Boulevard through Japanese Gulch and create a bypass of the Mukilteo ferry terminal has been a part of the city's transportation plan since 2001, but has not been built.[32][33] WSDOT estimated, during its annual AADT survey, that 21,000 vehicles used the highway in 2012.[14]

• Media related to Washington State Route 525 at Wikimedia Commons
• Highways of Washington State
• Whidbey Island Scenic Byway