SR 18 ramps: More traffic and detours ahead in Federal Way

Map of the proposed changes from Triangle Project construction in Federal Way. - Courtesy image
Map of the proposed changes from Triangle Project construction in Federal Way.
— image credit: Courtesy image

City officials are expecting a “significant increase in traffic” on the streets of Federal Way starting at 5 a.m. Monday.

According to the Washington State Department of Transportation, the ramp from westbound Highway 18 to northbound Interstate 5 will close Aug. 8 through Sept. 1. Also, the ramp from Weyerhaeuser Way to westbound Highway 18 will be closed until later this month, according to WSDOT.

The closures are part of the ongoing $112.5 million Triangle Project, which refers to the interchange in Federal Way where Highway 161 (Enchanted Parkway), Highway 18 and I-5 all meet. The interchange has long held a reputation for being dangerous for drivers. Federal Way and King County officials have been working to fund the project for more than a decade.

“This is going to be a major road closure,” said Jessie Hannahs, a senior traffic engineer for Federal Way. “Unlike past closures of ramps, this one will be a 24/7 closure. In the past, they have been just nighttime closures.”

Detour alert

There will be a signed detour route that will take drivers wishing to get on northbound I-5 onto Pacific Highway South and then to S. 320th St. But the detour will bring hundreds of vehicles through the city’s streets.

According to Hannahs, traffic models have identified a total of eight intersections that will see an increase in volumes during the afternoon/evening rush, and 12 intersections will be adversely affected during the morning commute.

“Our understanding is that the first couple of days will be the busiest and most congested while drivers identify the fact that it’s occurring and looking for alternate routes,” said Federal Way Mayor Skip Priest.

To counteract the increase, the city’s traffic engineers will be monitoring the intersections starting Monday and adjusting the timing of traffic signals, Hannahs said.

“There has been communication between WSDOT, Federal Way and Auburn, and on the day of the ramp closures, city traffic engineers will be out in the field, monitoring and making changes as we see needed to decrease as much delay as possible on city streets. We don’t anticipate what we put out in the field (to start) will be perfect. We will be making some changes.”

The massive Triangle Project is actually ahead of schedule for completion in “early fall of 2012,” according to Aleta Borschowa, a project engineer for WSDOT. Original estimates had the project opening to the public in April 2013. Mowat Construction broke ground on the two-and-a-half-year project in August 2010.

The project is in the first of two phases. The opening phase will eliminate the current cloverleaf loop ramps and replace them with flyover ramps for westbound Highway 18 to southbound I-5 and eastbound Highway 18 to northbound I-5. Direct access will be provided to Highway 161 from southbound I-5 and westbound Highway 18 through the construction of new exit ramps at South 356th Street and South 359th Street in Federal Way.

According to WSDOT, when the I-5/Highway 18 interchange opened to traffic in the early 1960s, its cloverleaf design was state of the art in freeway design.

But the light traffic volumes during that time concealed the major flaw of the cloverleaf interchange: the weaving that occurs when traffic merges on and off the freeway. Weaving causes congestion and increases the potential for collisions.

In the past five years, 604 accidents have occurred on Highway 18 near the I-5 interchange, said Paula Hammond, WSDOT secretary.

During the 1960s, the two major thoroughfares each carried less than a quarter of the traffic they do now, according to WSDOT numbers. The existing loop ramps are substandard and are high-accident locations. These improvements will improve traffic flow and safety at this increasingly congested interchange.

The project will modify the I-5/Highway 18 interchange to eliminate weaving vehicle movements. The project is expected to improve existing and future traffic flow; reduce the number and severity of accidents in the vicinity of I-5, Highway 161 and Highway 18; and avoid or reduce the effects on the environment.


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