Lynnwood link extension is a proposed 13.7km-long new light rail link between Northgate and Lynnwood in Seattle, Washington, US.

The project is being executed by Sound Transit, with construction works scheduled to begin in early-2018 and expected to be completed by 2024. It is estimated to have an investment of $3.07bn.

The light rail extension is expected to reduce travel time by offering a fast, frequent and reliable connection between Lynnwood and Northgate. The extended line is expected to serve between 63,000 and 74,000 passengers a day by 2035.

Lynnwood link extension background and development details

The economic development and population growth along the I-5 corridor have resulted in traffic congestion during peak hours.

Sound Transit has proposed the Lynnwood link extension to solve the traffic congestion issue, providing a reliable light rail system between south Snohomish County and the University of Washington, downtown Seattle and Seattle-Tacoma International Airport.

Apart from complementing the regional multimodal transportation connections, the extension will address the issue of overcrowding caused by insufficient transit capacity.

The project forms a major part of Sound Transit’s public transit system extension authorised by voters in 2008. The alternatives analysis and scoping of the project were completed between 2010 and 2012.

The final environmental impact statement for the project was issued in April 2015. Sound Transit received a record of decision from the Federal Transit Administration (FTA) in July 2015.

The final design phase began in 2016, while the permitting process is expected to be completed by 2018.

Lynnwood link extension route and station details

The Lynnwood link extension will continue along the I-5 corridor and include four new stations at Northeast 145th Street, Northeast 185th Street, Mountlake Terrace Transit Centre and Lynnwood Transit Centre.

“Sound Transit has proposed the Lynnwood link extension to solve the traffic congestion issue, providing a reliable light rail system.”

The stations will feature parking garages, bus drop-off facility, elevators, elevated platforms and noise-blocking walls, ticket machines and information kiosks, and public restrooms.

The extension will also have provision to add new stations at NE 130th and 220th streets in the future subject to the availability of funding.

Rolling stock

The trains on the extended line will travel with a four-minute headway during the peak weekday commutes. The journey from Lynnwood to downtown Seattle will take 28 minutes.

Each car will be capable of accommodating approximately 200 passengers, up to four bicycles, four wheelchairs, and multiple suitcases.

Construction details

The light rail link extension will be built in sections with major construction works taking two years or more to complete. Several streets along the I-5 corridor will be closed during the construction.

The NE 145th station will be installed with two sculptures named Helical Sine Wave Trusses, which will allow the flow of stormwater from the station’s garage roof into a mitigating bog and landscape.

Proposed alternatives

The alternatives that have been evaluated for the Lynnwood link extension included no-build alternative and several other light rail alternatives divided into three segments based on the geographical location.

Segment A included six alternatives between Northgate in Seattle and NE 185th Street in Shoreline, on the east side of I-5 corridor.

Segment B encompassed four alternatives between NE 185th Street in Shoreline and 212th Street SW in Mountlake Terrace.

Segment C provided three alternative departures from I-5 corridor to reach the Lynnwood Transit Centre station, with park-and-ride facilities at the station.