Traffic was slowed to a crawl in the Lower Queen Anne area on Saturday - all part of the Mercer Mess and some new changes made it even messier.

State Route 99 is fully closed between Valley Street and the southern end of the Battery Street Tunnel and crews have also shut down Mercer Street between 5th Avenue North and Dexter Avenue North.

Those roads will re-open on Monday.

Starting Monday, a five-block stretch of Eastbound Mercer Street will go from four lanes to two and will stay that way for 2 1/2 years. Drivers who use the road to get to Interstate 5 are being urged to get used to it and change their driving habits.

We re counting on people to make some different choices, said Eric Tweit, Seattle Department of Transportation's West Mercer project manager.

Map of the Mercer West changes | detour map

The latest phase of the so-called Mercer Mess project began Thursday with lane closures. The Seattle Department of Transportation said road crews will remove sections of the Aurora Avenue bridge structure, which goes over Mercer Street. Both Mercer Street and the overpass are being made wider as part of the deep bore tunnel project.

Two lanes of Mercer Street and the adjacent sidewalk, between 5th Avenue and Dexter Avenue, will be closed between 9 a.m. and 4 p.m. Friday. Two lanes of eastbound Mercer and one sidewalk will remain open.

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Starting Friday at 11 p.m., Aurora Avenue and Mercer Street will be completely closed to traffic in the area. It will reopen at 5 a.m. Monday. During the closure:

  • State Route 99 will be fully closed between Valley Street and the southern end of the Battery Street Tunnel. Traffic traveling through Seattle via SR 99 will be directed to I-5 north of Seattle at 85th Street or south of Seattle at East Marginal Way.
  • Mercer Street will be fully closed to traffic between 5th Ave. N and Dexter Ave. N. Traffic heading east towards I-5 will be detoured to Denny Way at 5th Ave. N and will reconnect to Mercer St. at Dexter Avenue N. to continue east.
  • Sidewalks will be closed on both side of SR 99 between Thomas and Valley Streets and on the south side of Mercer St. between 5th Avenue N. and Dexter Avenue N.

SDOT said drivers should expect significant delays and plan other routes.

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The lane restrictions will expand Monday. Two eastbound lanes of Mercer Street will be closed between 4th Avenue North, next to McCaw Hall, and 9th Avenue North. To help ease congestion, eastbound Broad Street will open as an alternate route for the first time since 2010. Despite that, drivers should expect delays.

SDOT said it will made signal modifications at 5th Avenue North and Harrison Street as well as Harrison Street and Broad Street in order to improve access to Broad Street.

Left turns from both directions of Mercer Street onto 9th Avenue N. will be restricted. SDOT said drivers heading north towards Westlake and Fremont should use Dexter Avenue N to reach their destinations.

  • Local access will be maintained at Taylor Avenue N.
  • The sidewalk on the north side of Mercer Street will be closed between 5th Avenue N. and Dexter Avenue N. The sidewalk on the south side of Mercer Street will remain open.
  • SR 99 traffic will be shifted to the west side of the roadway between Valley and Harrison streets. Two lanes of SR 99 in each direction will remain open.
  • The northbound SR 99 off-ramp to Mercer St. will be permanently closed. A new signalized intersection at Republican Street and Dexter Avenue N. will be available for northbound SR 99 traffic to reach South Lake Union.

If you are further to the west at Seattle Center, Queen Anne and Magnolia, we re encouraging people to go south downtown either to Denny or even to go along the north side of Queen Anne and Nickerson and come down Westlake if you re going to I-5, said Tweit.

It s going to be frustrating for both drivers and businesses in the area.

I hear a lot of horns honking a lot of people frustrated. Not only do customers come in frustrated, but it's an issue for most of employees, too. The construction is going to be headache commuting and getting here on time, said Mike Gentry, an employee at the Guitar Store in the Mercer corridor.

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