Drivers using Interstate 90, especially commuters from Mercer Island to Seattle, can expect more traffic jams when the center roadway is closed to deliver voter-approved light rail to the Eastside.

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Last week, a red sedan exiting the Mount Baker tunnel stalled on eastbound Interstate 90.

The road had been re-striped, with no right shoulder to pull onto. For 14 minutes, the car blocked the lane, until a state response truck arrived.

This rush-hour delay appears to be the first traffic jam related to the re-striping of I-90 across Lake Washington to prepare for light-rail construction in the center express lanes.

This weekend the express lanes will permanently close and restriping of other lanes will be completed before Sound Transit contractors take over this month.

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And whether you’re leaving Mercer Island, or simply crossing the lake, your drive will require more concentration, and often more time.

One new high-occupancy vehicle (HOV) lane is being squeezed into each direction of the freeway mainline. Some tunnel lanes are as narrow as 10 feet. Shoulders have been removed or reduced. And there are fewer entrance ramps on Mercer Island.

This weekend marks the end of an era for island drivers. Since 1989, they enjoyed unique access to the express lanes, a deal the city made to keep its commuters from drowning in regional traffic drawn by past I-90 expansions.

Late negotiations this spring to help Island commuters failed, so the city filed a lawsuit against the state and Sound Transit. Early Thursday morning, the Mercer Island City Council announced it had approved a “tentative” settlement agreement with Sound Transit. Under the agreement, Sound Transit would pay Mercer Island $10 million.

Someday the efficiency of rail, going from downtown Bellevue to International District/Chinatown Station in 19 minutes, will help thousands leave their cars behind, and serve people who now ride buses.

Sound Transit estimates the $3.7 billion East Link route to Overlake, to open in 2023, will carry 50,300 riders a day in 2030, plus 8,000 in a 2024 extension to Redmond.

Cross-lake trips

The lane conversion on I-90 will disrupt merge patterns and probably worsen traffic slowdowns by a few minutes, between the Eastside and Seattle.

The Washington State of Department of Transportation (WSDOT) chooses to accentuate the positive, by extolling “round the clock” high-occupancy vehicle lanes.

“We are excited to wrap up work on the new HOV lanes that will provide transit, carpools and van pools a more reliable commute that doesn’t depend on the direction of the express lanes,” WSDOT project engineer Aleta Borschowa stated. (The express lanes pointed toward Seattle mornings and Bellevue evenings.)

For general traffic, the state’s traffic study, written in 2006, predicted delays when carpools enter on right-side onramps and weave toward left-side HOV lanes.

Drives from Bellevue Way to Seattle could take nine minutes longer, the study said, but the impact would be less eastbound, and rail would eventually boost overall mobility.

A chokepoint already has formed near Mount Baker Tunnel. Eastbound drivers entering from Rainier Avenue South lost their leisurely merge lane in May, when restriping placed two lanes instead of one approaching the right tube of the tunnel.

More lanes have been reduced to 11 feet instead of the full-size 12 feet. WSDOT ultimately decided to stripe some 10.5-foot lanes on the floating bridge, leaving shoulder room for emergency and towing crews to work safely.

Bridge shoulders westbound are on the left, because drains, slopes and a center barrier built in 1989 prevent a traffic lane there.

Volumes will increase by 15,000 daily vehicles, being diverted from express lanes into the mainlines. Traffic may take months to settle into a pattern, WSDOT says.

Island commuters

Islanders have long known of the 1976 agreement designating the center roadway for transit, and that someday they could lose their access to speedy express lanes.

Another change may loom larger. Island entrances to westbound I-90 will decrease permanently from five to three on Sunday.

Traffic from three areas — the north side, downtown and Island Crest Way — will be channeled to the I-90 ramp at 76th Avenue Southeast. Cars will have to stop for meter signals, then dart into a filled westbound freeway lane.

Riders on the popular Route 550 express bus, already losing the South Bellevue Park-and-Ride for five years, might get caught in the backups between the Mercer Island Park-and-Ride and I-90.

To provide some relief, Sound Transit is funding signals and a short bus lane on North Mercer Way at 76th, which is among four intersections being modified. Still, that’s enormous pressure in one spot. Congestion there is expected to spread to downtown.

“We’re like ants. We’ll find a way to get to that point, and what that path will be. What will be the impact of 1,000 to 1,200 vehicles a day, in a downtown that isn’t even big enough now?” says Elizabeth Buckley, a citizen advocate and opponent of the I-90 changes.

A report by Sound Transit in April asserts “overall mobility for people traveling to or from Mercer Island will remain the same or be improved” even during construction. For instance, carpoolers would save 2 ½ minutes because they’ll have an HOV lane to Seattle in the afternoon.

A closer look shows solo drivers now using the Island Crest Way onramp will lose five to nine minutes overall going to Seattle, at morning peak. But time savings elsewhere, especially for bus riders reverse commuting, will even the scales, it says.

That argument didn’t impress Mercer Island Mayor Bruce Bassett.

“If I’m the guy who lives here and has to get to Seattle, I’m not OK,” he says.

Islanders took a hit last week in a Federal Highway Administration letter denyingthe city’s request — co-signed, among others, by King County Executive Dow Constantine and WSDOT Secretary Roger Millar — to let solo drivers enter the left-side HOV lanes at Island Crest Way, then merge into general lanes after reaching the straight floating bridge. Such maneuvers might obstruct regional buses and reduce the HOV lane below its 45 mph standard, a problem that would be reduced with ramp-metering.

Mercer Island says it will ask members of Congress to intervene.

A temporary city utility tax averaging $78 per household will be collected to pay part of costs associated with the lawsuit, which alleges that state and transit officials have failed to provide Mercer Island with sufficient highway access.

Bassett suggests Sound Transit:

• Hand over the 477-stall park-and-ride to Mercer Island, to be reserved for island residents. Half its parkers arrive from outside, filling the garage early.

• Pay for island circulator buses that meet I-90 express buses.

• Add trips on King County Metro’s limited Route 630 to downtown Seattle and First Hill. Send it directly from Island Crest Way into the HOV lane, instead of crawling to I-90 from the park-and-ride.

Sound Transit will consider leasing temporary parking lots on the island and shuttle buses, spokesman Geoff Patrick said. It won’t relinquish the park-and-ride garage, built with regional taxes.

“It is not possible to create the major benefits that are provided by high-capacity, congestion-free rail service without facing impacts during the construction period. Bellevue and Redmond residents are also going through sacrifices during East Link construction. Mercer Island is fortunate to be the only city along the East Link alignment not facing a significant park-and-ride closure during construction,” a statement said.

Congestion next week will create such an immediate backlash, predicts House Transportation Committee Chairwoman Judy Clibborn, D-Mercer Island, the transit board will have to restart talks with the city.

City newsletters urge residents to form carpools.