In the 2000s, WSDOT began a series of construction projects on sections of the SR 203 corridor that aimed to improve traffic congestion and increase road safety. A roundabout was constructed in southern Duvall to replace the unsignalized intersection at Northeast 124th Street in 2004, the first to be built on a rural highway in Western Washington, and received favorable feedback from local residents. WSDOT completed construction of a second roundabout in 2008 at the highway's southern terminus with SR 202 in Fall City, costing $4 million. A 2004 study of potential improvements to SR 203 also suggested the addition of a rumble strip in the road's centerline, along with hard landscaping to force motorists to slow down when entering populated areas. A fish culvert on Loutsis Creek was replaced by a composite arch bridge in 2020, the first of its kind in the state.