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The intersection of Ash Way and 18th Avenue West is nestled in a busy urban setting with sensitive environmental features. To the north, a residential area and school creates a daily stream of pedestrians and bicyclists. Less than a quarter mile to the south, a Park-and-Ride and I-5 on-ramp services a mass of commuter traffic. To safely accommodate all users and relieve traffic congestion, Snohomish County selected a modern roundabout with added pedestrian and bicycle facilities.
WHPacific’s design incorporated a reverse curve alignment for the south leg of Ash Way, allowing the roundabout location to shift southwest. This location provided multiple benefits; not only did it take full advantage of the available triangle-shaped property, it also made construction possible without impacting the adjacent wetlands and stream crossing.
Most importantly, the design met the key project challenge of increasing the intersection’s safety by reducing vehicle speeds to less than 20mph.
AWARD: 2009 ACEC Washington - Engineering Excellence Bronze
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