Overview
The I-405/SR 167 interchange was one of the state's worst traffic bottlenecks. One factor in the bottleneck is the merging conflict on the collector-distributor route that separates from the mainline of southbound I-405 at the interchange. In the prior lane configuration, traffic exiting the collector-distributor to southbound I-405 crossed traffic entering the collector-distributor from northbound SR 167. These weaving movements resulted in accidents and increase congestion on both southbound I-405 and northbound SR 167.
This project built a grade separation ramp connecting the southbound I-405 offramp to the southbound SR 167 on-ramp to reduce congestion (see a before-and-after driving map). Crews also realigned the ramp from southbound I-405 to northbound SR 167 to accommodate new ramp.
 | Improves Safety
The new ramp reduces the risk of accidents by separating traffic entering and exiting I-405 at SR 167. WSDOT traffic engineers expect this project to cut accidents on the collector-distributor by 30 percent This project also upgrades safety features in this location to current highway design standards.
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 | Relieves Congestion
The ramp helps reduce congestion by eliminating the weaving motion between the I-405 southbound on ramp from SR 167 and the I-405 southbound off ramp to SR 167 by providing a separate elevated lane for traffic heading to southbound SR 167.reduce congestion on southbound I-405 and northbound SR 167 during non-peak hours.
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 | Protects Environment
This project contains features that improve the environmental attributes of the area. These include:
• A state-of-the-art emerging technology stormwater treatment facility inside the loop ramp in the northeast corner of the interchange. In this facility, an S-shaped series of shallow ponds progressively filters stormwater runoff before it is discharged into a nearby stream.
• Improving the buffer of Springbrook Creek on city of Renton property to compensate for the removal of trees in the Rolling Hills Creek buffer.
• Landscaped plantings within the interchange area designed by WSDOT architects. The plantings include a variety of native trees and wetland grasses that will enhance the aesthetics of the interchange.
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 | Economic Incentive
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Partnerships & Cooperation
The project worked with the city of Renton to improve the buffer of Springbrook Creek on city property. This compensated for the removal of trees in the Rolling Hills Creek buffer.
Funding
This project was funded through the following sources:
- Existing Funds - $9.96 Million
- Total Funding Available From All Sources - $9.96 Million
Contact Us
Assistant Project Engineer Mark Sawyer
WSDOT Kent Design/Construction Office
21851 84th Ave. S.
Kent, WA 98032-1958
Phone: 253.872.2958
E-mail: sawyerm@wsdot.wa.gov
Public Information Officer - Myly Posse
15700 Dayton Avenue North, MS-103
Seattle, WA 98133
(206) 440-4700
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