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Staff recommends Duff Avenue 'road diet' in long‑range corridor plan to improve safety and walking access
Summary
City staff presented a long-range vision for Duff Avenue that would convert most four-lane undivided segments to a three‑lane cross section with a shared-use path, arguing modeling shows similar traffic operations while improving pedestrian and bicycle safety; council asked for additional local crash modeling and outreach clarifications.
City transportation staff proposed a long-range redesign for Duff Avenue that would convert most four-lane undivided segments to a three‑lane cross section with a center two‑way left‑turn lane and an 8‑foot shared‑use path on the west side. The presentation, given July 21 during a special Ames City Council workshop, framed the change as a safety- and multimodal‑first approach while keeping traffic operations acceptable under conservative growth assumptions.
"The 3‑lane section advances the priorities established in many of the city's plans — safety for all users, safer pedestrian crossings, walkability and bikeability," said Kyle Thompson, transportation planner for the City of Ames. Staff showed corridor volumes between about 9,000 and 12,600 vehicles per day today and used a conservative 0.5% annual growth rate to forecast to 2050. Using 85th‑percentile count data and microsimulation, staff reported only small differences in intersection delay between the existing 4‑lane and proposed 3‑lane sections — typically about one to two seconds at most.
The technical presentation emphasized that a 3‑lane cross section allows dedicated left‑turn phases at signals and creates opportunities for median refuges at crossings such as 12th Street by the Mary Greeley medical campus. Staff also showed local precedents — South Dakota Avenue in Ames operates as a 3‑lane segment at comparable ADT — to illustrate feasibility.
Council members asked staff to drill down on the expected safety benefits for Duff specifically. "The 19 to 47 percent crash‑reduction range you cite — is that national or Duff‑specific?" one councilmember asked. Thompson replied that the 19–47% figure is national and agreed to produce Duff‑specific modeling or a clearer local estimate in the final report.
Staff stressed the corridor plan is a guiding, phased document (10–20 year horizon) and not a construction commitment; final project designs and CIP programming would return to council for approval. The study team plans to bring the finalized report back in the fall for direction and acceptance.
