From Sound Transit:

On June 3, 2017, WSDOT and Sound Transit are scheduled to open a new HOV lane in each direction on Interstate 90 between Mercer Island and Seattle and permanently close the center roadway express lanes. This will allow Sound Transit to start construction of the 14—mile East Link light rail extension from Seattle to Redmond.

This is a change for I-90 commuters and everyone that uses I-90 across Lake Washington and it will take time for people to adjust to new habits and traffic patterns. It could take months for traffic to settle into its new routine. There will be three general purpose lanes for single occupant vehicles traveling on I-90 and an HOV lane in each direction. More information can be found here.

HERE'S WHAT TO EXPECT:

Single occupant vehicles traveling between Mercer Island and Seattle

• All traffic to and from Mercer Island will use the I-90 mainline.
• Single occupant vehicles will no longer have access to westbound I-90 at Island Crest Way. Drivers will need to use 76th Avenue Southeast, East Mercer Way or West Mercer Way to access westbound I-90.

Carpools and vanpools traveling between Mercer Island and Seattle

• Carpools and vanpools traveling between Mercer Island and Seattle can use the new mainline HOV lanes.
• Note: The 5th Avenue South ramp in Seattle will become bus only.
• Drivers heading from Mercer Island to Seattle can get on westbound I-90 at Island Crest Way.
• Later this summer, carpools and vanpools heading from Seattle to Mercer Island will be able to exit from the eastbound I-90 HOV lane directly to Island Crest Way.

Bus riders

• There are no changes for bus riders traveling to and from the Eastside via I-90.
• The I-90/Rainier Avenue Freeway Station will continue to operate until September 2018 when Sound Transit begins construction on the Judkins Park Light Rail Station.
• When the I-90/Rainier Avenue Freeway Station closes buses will use Fourth Avenue South and Rainier Avenue South to travel between downtown Seattle and I-90.