New ramp metering to help provide better I-405 traffic flow

A new congestion-busting tool will be ready for action next week to help with the occasional afternoon backups on southbound Interstate 405 through Renton.

Beginning Sept. 16, the Washington State Department of Transportation will start metering the on-ramp from Sunset Boulevard to southbound I-405. The ramp meter will only activate when traffic on southbound I-405 dips below the posted speed limit.

Ramp metering works by using a stop light to evenly space vehicles as they enter the highway. Drivers will briefly wait at a stop light on the end of the ramp and proceed when it turns green at a pace that allows for easier merging and better traffic flow.

"This is a proven tool that helps improve travel times on the highway, and reduce merge-related collisions by at least 30 percent," said WSDOT traffic engineer Mark Leth.

Like all metered on-ramps, WSDOT will monitor the need for activation daily while keeping an eye on the nearby surface streets. Drivers will notice the Sunset Boulevard meter may be dark some days when traffic is light and active on days when delays from State Route 167 create significant backups.

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