Planning for the Transit Interchange

East Link light rail is currently under construction with service set to begin in 2023. One of the remaining issues under discussion regarding light rail on Mercer Island is the integration of the new rail service with existing bus transit at the Mercer Island Station. Sound Transit and King County Metro are seeking to minimize overlap between light rail and bus service along I-90, maximize transit efficiency and reduce air pollution.

A 2017 Settlement Agreement between the City of Mercer Island and Sound Transit sought to balance the goals of the transit agencies with the City’s desire to protect quality of life for Island residents. The Settlement Agreement outlined the location and design of the Transit Interchange, identifying a roundabout at North Mercer Way and 77th Ave SE as the location for bus loading/unloading and turnaround.

King County Metro was not a party to the Settlement Agreement, but it was known when the agreement was signed that Metro would need to be involved in planning and implementation of the transit interchange. Thus, after the Settlement Agreement was signed, Sound Transit commissioned the Mercer Island Transit Interchange Operational and Configuration Study (Full Study; Exec Summary) to evaluate how Metro buses will integrate with the light rail station. Since the study was completed, Sound Transit and Metro have been working to further refine plans for the interchange, including the design of the improvements to the right of way, the roundabout, bus queueing and layover areas, and pedestrian, bicycle and vehicle circulation.

Throughout early 2019, the City Council has also been in discussion with the transit agencies about expected bus operations and the design details of the proposed interchange. The City Council held two Study Sessions (19 March and 30 April, 2019) at which Sound Transit and Metro presented updates on roundabout design and proposed future bus operations. Meeting materials, FAQ, and comments/questions are provided in the articles below.