Iowa DOT backs 2x1 roundabout for Willis Avenue at Highway 141; Perry to update RISE application

PERRY — City staff, a consultant team and Iowa Department of Transportation engineers on Thursday told the Perry City Council that the agency’s preferred fix for the Willis Avenue–Highway 141 intersection is a two-lane-to-one-lane (2x1) roundabout, based on safety and traffic forecasts.

Consultant Jennifer McCoy, a senior traffic engineer with Bolton and Inc., told the council that the intersection currently has a high share of angle crashes: "over 50% of our crashes at the intersection are broadside or angle type crashes," and nearly half of recorded crashes there have resulted in injury. She said study modeling that included two near-term developments (JBS and ADR) and a conservative 50% growth projection for the industrial park showed the existing two-way-stop control would degrade to Level of Service F in the near term without changes.

The consultant team analyzed three alternatives: a conventional traffic signal with turn lanes, a multi-lane (2x1) roundabout and a reduced‑conflict intersection (RCI or J‑turn). McCoy summarized the tradeoffs: the signal would meet MUTCD warrants and improve some operations, but a 2x1 roundabout "has been shown to have a 40% reduction in all types of crashes and an 80% reduction in those serious crashes," while the RCI was not carried forward because side‑street and heavy truck volumes make it a poor fit.

Iowa DOT District 4 traffic engineer Austin Yates said the DOT weighs mobility, accessibility and safety when deciding primary‑system projects. "Mobility is number one... underpinning everything is safety," he said, and noted that while signals can improve accessibility they can shift crash types — reducing broadside crashes but increasing rear‑end crashes — a finding echoed in recent Iowa State research the presenters cited.

DOT district engineer Scott ShraMM and other DOT staff discussed why a grade separation (overpass) was impractical at this time: it would require extensive ramps and earthwork, significant right‑of‑way impacts and much higher cost. ShraMM said interchange construction can range widely in cost and is typically considered only when surface intersections have broken down over a multi‑decade planning horizon.

Design details presented included truck aprons and turning radii to accommodate semi‑trucks, a potential northbound slip/bypass lane for heavy northbound movements, pedestrian median refuges for staged crossings, and advisory approach speeds of about 20–25 mph through the roundabout.

City staff and consultants outlined a near‑term schedule tied to the RISE grant process: staff will update a RISE resolution for the council agenda on Monday to reflect the current concept and cost estimates for the intersection and Sumis Avenue work; that updated material would go to the DOT commission (penciled in for April 14) for funding consideration. Consultants estimated a year for design and a construction window staged over two seasons; if approvals and funding proceed, earliest construction was discussed as mid‑2027.

No formal council vote on the intersection occurred at the session. Staff said that if the city chooses not to pursue the RISE path now, DOT could place the project on a five‑year plan and pursue the improvement on its schedule. City staff asked for input on pedestrian and trail connections and other local details to include in the updated resolution and cost estimate.

Council members raised concerns and alternatives during the discussion. One council member repeatedly asked whether a grade separation could be used instead of an at‑grade fix; DOT staff described that option as "impractical" for the near term because of land impacts, drainage and cost. Members also asked about business and truck impacts during construction, and consultants said the roundabout can be built in phases without a full closure and that truck turning paths and a bypass lane were part of the design dialogue.

The next formal step the council was asked to consider is the updated RISE resolution on the upcoming council agenda; if the RISE funding package and DOT approvals move forward, the city would issue a design contract and hold public engagement through the design process.

Meeting participants who spoke on the record included Jacob Erenss (consultant), Jennifer McCoy (senior traffic engineer, Bolton and Inc.), Austin Yates (Iowa DOT District 4 traffic engineer) and Scott ShraMM (Iowa DOT District 4 engineer).