Speed limits on Aurora Avenue North, Lake City Way and other state-owned streets that run through Seattle are being lowered by 5 mph, the city and state transportation departments announced Monday.

Crews began installing 150 new — and in some cases larger — signs along state roadways Sunday, bringing the highest speed that drivers are permitted to travel in the city down to 40 mph, with the exception of Interstate 5, Interstate 90 and Highway 99 inside the tunnel. New signage on Aurora is expected by mid-April.

The updated speed limits follow an announcement from Mayor Jenny Durkan in 2019 that her administration would lower speeds on all city arterials to 25 mph.

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As of this month, crews have installed about 2,500 signs on about 415 miles of streets — nearly 90% of major roadways in Seattle — posting the 25 mph limit.

But because the state shares control with Seattle over Aurora, Lake City Way, Sand Point Way, Northeast 145th Street, East Marginal Way and West Marginal Way, Durkan’s 2019 order did not immediately apply to those roads.

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It took time for the Seattle Department of Transportation (SDOT) to “go through the processes” with the state, said SDOT spokesperson Ethan Bergerson.

Last week, the state Department of Transportation (WSDOT) approved Seattle’s request to lower speeds on portions of state routes that run along surface streets in the city.

“We worked very closely with the city of Seattle on this,” said WSDOT spokesperson Bart Treece. “Together, we are committed to finding new and creative ways to make safety improvements to drive serious injury and fatality numbers down to zero, because one is too many.”

The state-owned roadways may see further reductions. “Anything above 30 mph, we’re going to continue to evaluate,” Bergerson said, but he could not provide a specific timeline.

Even with fewer people commuting and traffic volumes at historical lows due to the coronavirus pandemic, Seattle recorded the second-highest number of people killed in traffic-related crashes in a decade last year.

State highways that look like city streets but are designed for more traffic often see a disproportionate share of the collisions.

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In 2019, 14 crashes that resulted in serious injuries or deaths occurred along Aurora, and nine more occurred last year, according to SDOT. Lake City Way saw three serious or fatal crashes in 2019 and three more in 2020.

“The loss of lives — often our most vulnerable travelers — due to crashes and collisions on our streets is unacceptable,” Mayor Jenny Durkan said in a statement Monday. “Seattle has been a national leader in lowering speed limits throughout our city, and we are proud to work with WSDOT to roll out speed reductions on state routes in Seattle so all travelers are safe getting to where they need to go.”

SDOT says the simple changes can make a difference.

In an SDOT study of five neighborhoods in north Seattle, data showed that lowering speed limits and increasing the number and frequency of speed-limit signs — without any additional engineering, education or enforcement — resulted in lower speeds and fewer crashes.

The study, which published last summer, compared five years of data between 2013 and 2018 with about one year of data between 2018 and 2019. In locations with new 25 mph speed-limit signs spaced a quarter mile apart, crashes dropped 22%, the study found.

Still, Bergerson said these lower speeds are “just one part of the picture.”

For example, SDOT is also working with WSDOT to repave Lake City Way and add other safety improvements.

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New sidewalks and curb ramps have been installed at Northeast 135th and Northeast 137th streets. Sidewalks and curb ramps will also be constructed at Northeast 82nd and Northeast 95th streets.

SDOT also anticipates receiving a grant from the state this year that would allow the agency to begin major design changes along Aurora. The $2 million would fund community engagement, right of way planning, traffic analysis and design.

The department will roll out educational campaigns to make drivers more aware of the new speed limits but has not asked for additional police enforcement.