36th Street/Hill Road/Catalpa Drive Roundabout Design

KAI produced a concept design report for the proposed six-leg, “dog-bone” shaped roundabout at the intersection of 36th Street, Hill Road, and Catalpa Drive in Boise, Idaho. Throughout the project, KAI staff maintained a sensitivity to pedestrian concerns, right-of-way and environmental constraints, and school access needs. One of many noteworthy challenges was the determination of the appropriate lane configurations on the Hill Road approaches, which included detailed investigation and post-processing of traffic model volumes, numerous collaborative meetings with ACHD and City of Boise staff, and application of sound engineering judgment. The ultimate resolution, which was approved by ACHD Commission, was to recommend and design multilane approaches, but allow for additional evaluation in future design stages. KAI developed sketch and CAD draft conceptual roundabout designs and estimated the overall construction cost for the preferred, multilane alternative. Throughout this project, KAI staff worked closely with ACHD staff to refine traffic volume scenarios, apply ACHD Roundabout Policy for evaluating natural paths, fastest paths, etc., and make reasonable design exceptions as needed.