From staff reports:

The Washington State Department of Transportation (WSDOT) reports that new ramp meters will help smooth traffic flow and ease congestion along 8 miles of Interstate 5 between Tukwila and Federal Way.

Crews will install ramp meters at four separate interchanges where traffic routinely slows to a crawl during the morning and afternoon rush-hour commutes.

New meters at all four interchanges — eight ramps total — should be in place by summer 2013. The project will cost about $1.4 million, according to WSDOT.

Traffic from the on-ramps is blamed for overloading I-5 during peak travel times. WSDOT reports that ramp meters will control the pace at which vehicles enter the freeway and keep traffic moving.

Ramp meters are proven to reduce collisions by 30 percent or more, according to WSDOT. Every minute a lane is blocked leads to four to 10 minutes of traffic delay.

Ramp meters are already in place at South 320th Street in Federal Way.

Contractor crews will begin installing meters along northbound and southbound I-5 beginning Monday, Aug. 20. The new meters will be located on the following ramps:

• S. 188th Street to northbound I-5

• S. 188th Street to southbound I-5

• S. 200th Street to southbound I-5

• State Route 516 westbound to northbound I-5

• SR 516 eastbound to northbound I-5

• SR 516 to southbound I-5

• S. 272nd Street to northbound I-5

• S. 272nd Street to southbound I-5

Drivers can expect daytime lane closures near each interchange and overnight ramp closures. Crews will also restripe the roadway, install warning signals and add signage.

The speed of traffic on I-5 in South King County has steadily dropped over the years. WSDOT reports that the average morning commute speed for northbound traffic is 37 mph between Federal Way and Tukwila. The average speed for southbound traffic in the evening commute is 40 mph.