Sound Transit and King County Metro provided an update to the Mercer Island City Council on East Link’s construction progress on Tuesday, March 19. The presentation also included information about the future Mercer Island Transit Interchange, which is the new name for the project formerly known colloquially as the bus intercept.
The general concept remains generally similar as previously reported, but at this time Sound Transit and Metro, in coordination with the City of Mercer Island, have made some refinements and identified options for Mercer Island to consider.
The Settlement Agreement which ended East Link-related litigation in 2017 abandoned the previous 80th Ave SE concept and instead mandated the roundabout at the intersection of 77th Ave SE and N Mercer Way to allow buses to turn around; required all regional bus drop-off, layover, and pickup to occur on the south side of N Mercer Way; and limited layovers to no more than 15 minutes, and only in the PM peak period. A diagram of the concept is shown below.
Under the Settlement Agreement, buses would exit the westbound I-90 HOV direct access ramp (1), circulate through the roundabout (yellow circle), then drop off passengers and layover (4) before picking up passengers at the existing eastbound bus bay (5) before re-entering I-90 via the eastbound HOV direct access ramp (6).
Metro expressed concerns about how the various provisions would limit future regional bus service and impact the implementation of Metro Connects. Metro and Sound Transit staff developed proposed changes to the physical configuration and to operations that would increase the number of buses that could use Mercer Island Station. Specifically, Metro requested the ability to drop off passengers earlier (2) to both facilitate quicker access to the station and improve the utility of the layover spaces, the use of layovers throughout the day instead of only during the PM peak, and the addition of more layover space (3). They also suggested the potential addition of an in-lane stop southbound on 80th Ave SE to serve Mercer Island local bus routes (7).
Metro and Sound Transit commissioned a report that analyzes various configurations to determine their ability to support bus service. The report estimates that infrastructure and operations consistent with the Settlement Agreement (the “Limited Service Configuration”) could support approximately 12 buses per hour, due to complications with bus movements for drop-off, layover, and pickup. Allowing passenger drop-offs at the existing westbound bus bay (the “Improved Service Configuration”) could support up to 16 buses per hour by improving ability to access layover areas, while the additional layover space described above (the “Optimal Service Configuration”) could support up to 20 buses per hour.
In response to questions from the Mercer Island City Council about South Bellevue, Katie Chalmers, Service Planning Supervisor for Metro, explained that South Bellevue Station’s bus layover capacity is already maximized with other bus service including I-90 express routes coming up I-405. In addition, buses already in the I-90 corridor coming from Eastgate, Issaquah, or Sammamish find it approximately 10 minutes faster to travel to Mercer Island compared to South Bellevue due to the HOV direct access ramps at Mercer Island and the distance of the South Bellevue Station from I-90. As Metro’s intention is to not run any service across I-90 to Seattle once East Link opens, without Mercer Island, Metro would likely have to send buses to Bellevue Transit Center instead.
Metro has not identified a specific service pattern for I-90 service at this point, and won’t begin this process until 2021, two years before East Link opens. The general concept is to provide service to at least the same destinations as today (Eastgate, Issaquah, Sammamish) and reinvest service hours presently spent getting to and through downtown Seattle back into service on the Eastside. This could lead to improved service frequency, more destinations, or a combination of both.
In response to questions about train capacity Sound Transit’s Mike Bell, Executive Project Director for East Link, and Luke Lamon, Government and Community Relations, noted that peak headways are anticipated to be every 6 minutes (author’s note: 6 minute peak headways may be referring to ST3 buildout and not the anticipated ST2 service plan, which is for 8 minute peak headways) using 4-car trains, which can carry approximately 600-800 passengers depending on how tightly people are willing to squeeze onto trains. Katie Chalmers noted that peak bus ridership on Metro’s service in the I-90 corridor (e.g. excluding the 550 and 554) is between 6-7,000 per day, which is easily accommodated by East Link.
The Mercer Island City Council had additional questions and concerns about project impacts, especially to the residential neighborhood north of N Mercer Way, and also about non-motorized station access and safety at the future roundabout at 77th Ave SE/N Mercer Way and at the 80th Ave SE/N Mercer Way intersection. The Mountains to Sound Trail runs along N Mercer Way in this area and is a heavily used bike route. Sound Transit recently made improvements at the Mercer Island Park and Ride to reduce pedestrian/bicycle conflicts, and is considering pedestrian and bike safety as the roundabout advances through design.
No decisions were made, although Sound Transit indicated it needs a decision soon as construction of the roundabout and other improvements would start in late 2020 to be complete in late 2022 before East Link opens.