At a Nov. 9 community meeting to discuss the substantial changes to Interstate 90 when East Link light rail construction begins next year, residents heard from Mercer Island city staff, elected officials and consultants that the impacts of the center roadway closure could extend far beyond gridlock on the freeway.

The center roadway of I-90, which contains the reversible transit lanes that many Island commuters use every day, is planned to close in June 2017, and Sound Transit light rail service will begin in 2023. The permanent closure will result in significant changes to the configuration of I-90, and by extension, traffic patterns on city streets. The six-year construction period could be especially difficult for drivers, whose access recently became even more restricted.

The city commissioned a consultant, KPG, to analyze the worst case impacts on local Mercer Island traffic based on a decision by the Federal Highway Administration (FHWA) that Island commuters traveling alone will not be able to use ramps or lanes designated for high occupancy vehicle (HOV) traffic, despite agreements dating back to 1976 that guarantee that access.

Sound Transit and the Washington Department of Transportation (WSDOT) have been working to add one lane of traffic each way to I-90 (referred to by the city as the R8A lanes) and plan mitigation for cities affected by light rail construction.

The traffic analysis for the East Link Project assumed that the R8A lanes would be designated as HOV lanes, and that single occupancy vehicles (SOVs) traveling to or from Mercer Island would be allowed to use these lanes.

The city of Mercer Island was negotiating for benefits like more commuter parking and local bus service for its “loss of mobility” after the center roadway closure, until FHWA’s intervention threw a wrench in those plans. At the meeting, some residents expressed annoyance with this decision, while others questioned why the city didn’t see it coming.

Mayor Bruce Bassett said that the city shares the sense of frustration, and is negotiating to “get the best deal we can from what’s coming.” He said he thought it would be unproductive to try and stop light rail across I-90, especially after voters passed Sound Transit’s recent measure (ST3) expanding light rail service even more.

Bassett also said that FHWA’s current plan for Mercer Island is “unworkable.” The city, with Sound Transit, FHWA and WSDOT, came up with a list of alternatives to consider, and Bassett asked the community meeting attendees if they had anything to add to that list.

Residents like Tom Acker, who started the Save our Suburbs (SOS) community group and ran for City Council last year, said that Islanders may not have voted for Sound Transit’s measures if they knew about the consequences, and asked if there was a way to delay and/or shorten the closure period of the I-90 center lanes.

“There is a grim irony that light rail is projected to make mobility and traffic congestion worse throughout Mercer Island,” Acker said after the meeting.

Michael Lapham of KPG said at the meeting that the FHWA’s decision was made for lane performance, safety and legal reasons. KPG did not analyze the impacts of the planned changes on the freeway itself, but focused on the effects on local streets and intersections. KPG made a similar presentation at the Nov. 7 City Council meeting, analyzing different time periods: 2014 existing conditions, 2017 conditions during construction and 2035 conditions with the completion of the East Link Project.

According to KPG’s traffic simulations, the potential SOV restriction at the Island Crest Way westbound on-ramp would result in traffic being diverted to other I-90 on-ramps, which would increase traffic volumes on local streets and negatively impact traffic operations in and around the Town Center. The Level of Service (LOS) could drop below standards at three Island intersections in 2017 and three more in 2035.

Traffic volumes onto westbound I-90 are highest during the morning commute. Currently, the Town Center and Island Crest Way have SOV access onto westbound I-90 from three on-ramps: 76th Avenue Southeast, 77th Avenue Southeast and Island Crest Way. If the FHWA decision sticks, that would be reduced to a single on-ramp at 76th Avenue Southeast, which would carry almost 1,200 vehicles during the morning peak hour.

“The 76th Avenue Southeast on-ramp would not be able to support this level of traffic and would result in extensive queuing, travel delays and potential for traffic to divert to other westbound on-ramps such as West Mercer Way,” according to the KPG memo.

The north end of the Island may not be the only part affected. Island Crest Way, a principal arterial, carries 23,000 vehicles per day approaching I-90. Mercer Island’s transportation system is based on Island Crest Way forming the primary north-south transportation spine, providing access between I-90 and the southern three-quarters of the Island.

Currently, vehicles traveling between Island Crest Way and Seattle have direct access to westbound I-90 via a tunnel.

“Without additional improvements, congestion and queuing would increase the 2017 and 2035 AM peak hour travel times for SOV traffic between Island Crest Way and westbound I-90 by more than five minutes,” according to the KPG memo.

The SOV restriction would require westbound SOVs on Island Crest Way to exit the high speed arterial and drive an additional half mile on local streets to reach the 76th Avenue Southeast on-ramp. Most would travel on either North Mercer Way or the Town Center streets.

KPG’s traffic simulation modeling showed extensive queuing along North Mercer Way, with backups continuing onto Island Crest Way and into the Town Center. These added traffic volumes would also increase the potential for pedestrian-vehicle conflicts in the Town Center and impact bus operations around the light rail station. The changes to intersection operations should also be reviewed for consistency with air quality standards, according to KPG.

The city will use the results of the KPG traffic analyses in the continued negotiations with Sound Transit, WSDOT and FHWA to achieve the mobility goals of Mercer Island residents.

Sound Transit consultants are currently conducting studies on freeway traffic impacts, and studies are underway on four of the 12 alternatives identified by an interagency work group.

Interim City Manager Pam Bissonnette said that the city doesn’t like all of the alternatives, and in fact, opposes some of them. The city’s preferred alternative is the one that has already been assumed and studied: that Mercer Island SOV traffic will have access to the HOV lanes.

The way that this solution would be acceptable to FHWA is if the lanes were designated as high occupancy toll (HOT) lanes instead of HOV, meaning that single occupants would pay a toll to use the lanes, similar to on I-405. The freeway, and the ramps and intersections near it, are all controlled by WSDOT. Bissonnette noted that while the city has a seat at the negotiating table and is engaging its residents on the alternatives that would be most acceptable to them, “what happens on I-90 is not a local decision.”

After the city’s presentations, Bassett attempted to cut short the general question and answer period and move the citizens into small discussion groups, a move that was protested by the meeting attendees.

As the question and answer period continued, some residents asked about legal action to delay the closure of the center lanes until some of the issues are resolved. Bassett explained that while suing Sound Transit might help the city in one negotiation, it would hurt in the other, as Sound Transit is the city’s partner in its debate with FHWA. The city has both internal and external attorneys advising it, but going to court is not its preferred starting point, Bassett said.

Bissonette also said that the city’s police and fire departments are reviewing the impacts of the I-90 reconfiguration on emergency vehicle access. The restriping from three lanes to four will eliminate the shoulders on the floating bridge.

For more, see www.mercergov.org/rail and www.mercergov.org/R8A.

The closure of the I-90 center roadway will result in the following changes to Mercer Island’s access to and from I-90:

– The reversible ramp at 77th Avenue Southeast to/from the I-90 center roadway will be closed.

– The Island Crest Way westbound on-ramp to the center roadway will be closed and the on-ramp connecting to the I-90 mainline will be restriped to connect with the R8A lanes.

– The 76th Avenue Southeast on-ramp to westbound I-90 will be widened to include a metered general-purpose lane and a HOV bypass lane.

– The Island Crest Way eastbound off-ramp from the I-90 center roadway will be relocated to serve the new I-90 R8A lanes.

Correction: A previous version of this story stated that the community meeting was on Nov. 16. It was on Nov. 9.