DOT: Ramp metering from Mercer Street to I-5 kicks off March 10

The notoriously congested on-ramps from Mercer Street to Interstate 5 in Seattle will present motorists with a new wrinkle starting next month when ramp metering begins. (Photo: KOMO News)

SEATTLE - The notoriously congested on-ramps from Mercer Street to Interstate 5 in Seattle will present motorists with a new wrinkle starting next month when ramp metering begins.

Officials with the state Department of Transportation announced the upcoming change in a blog entry Thursday.

"Call it a clog, a slow-down, a standstill or some other colorful phrase, merging onto I-5 from Mercer Street in Seattle can be a trying experience, with backups extending beyond the length of the on-ramp to I-5," according to the blog entry. "Also exasperating - the I-5 drive through Seattle as the onslaught of slow-merging vehicles brings freeway traffic to a halt."

Transportation officials say new signals have been installed along the ramps and will be activated on weekends starting March 10. Weekday metering could begin as early as April 10.

The WSDOT blog says the ramp metering "will help to pace the merging vehicles" and created a video to show how it will work:

Transportation officials also gave this description of how the ramp metering will work:

- On Mercer Street, once you cross Fairview Avenue, you will have two lanes on the ramp to northbound I-5 and three lanes on the ramp to southbound I-5 where you can wait for your green light to merge onto the freeway. The signals will alternate traffic from each lane, and instead of a clogged ramp, picture more of a slow leak of vehicles onto I-5. Gaps between merging vehicles will make the merge easier and reduce the risk of collisions near the I-5 on-ramps.

- Traffic engineers will monitor congestion and travel times on I-5 to determine when to turn on ramp metering. In coordination with the Seattle Department of Transportation, they will also monitor and adjust the ramp metering when it is active. As far as backups and delays on Mercer Street itself, engineers do not expect any negative effect.

"Many of us can feel a bit stressed looking ahead to merging traffic. Whether merging lanes or merging from the on-ramp to the freeway, predicting fellow driver behavior can be taxing. The new signals will help to ease some of the anxiety by alternating traffic and taking out the guesswork," the WSDOT blog says.

Transportation officials say the ramp metering will create a steadier flow of traffic onto the freeway, reduce freeway travel times and reduce the severity and number of collisions due to merging traffic.

But commenters on KOMO's Facebook page were skeptical about the plan.

"This is not going to end well. It already can take over 30 minutes to get from Lower Queen Anne to the 5 fwy onramps," commented Doug Briggs.

Ryan Bates commented: "Metering won't work when the traffic is not moving anyways. this will just make the mercer corridor even worse than it is."

And Matt Hanaford commented simply: "As if mercer street weren’t bad enough already."

Undaunted DOT officials remained upbeat about the new approach, however.

"We are confident the new meters at this major downtown intersection will help move traffic out of the city safely and with more consistency," the blog says.

And the Seattle Transportation Department says not to worry.

It said in a statement: "The way WSDOT is proposing to meter the Mercer on-ramps should not significantly change how traffic operates on Mercer Street, day to day."

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