Council accepts concept study recommending diverging‑diamond design for I‑35/Shawnee Mission Parkway

The City Council accepted, by a 7‑0 vote, the Shawnee Mission Parkway and I‑35 interchange concept study prepared by HNTB, which recommends a diverging‑diamond interchange (DDI) coupled with intersection improvements at Antioch as the preferred alternative.

HNTB project manager Brent Gerard presented traffic modeling that showed heavy queueing and capacity issues at the I‑35 ramps and along Shawnee Mission Parkway. Gerard explained the study evaluated eight configurations, narrowed to three, and ultimately recommended two leading options; the DDI ranked highest across safety, traffic operations and cost categories. “The diverging diamond actually came out on top on every single category,” Gerard said, adding that Antioch intersection improvements are related but separate projects that materially affect the DDI’s performance.

Conceptual planning‑level costs presented to council were roughly $4,300,000 for the Antioch intersection work and a spread of $32,000,000 to $43,000,000 for the DDI depending largely on whether the adjacent BNSF bridge requires reconstruction. HNTB noted that the DDI reduces signal phases, shortens pedestrian crossing distances via mid‑block crossings and yields operational benefits, but said full benefits depend on coordinated Antioch work and partnership with KDOT for right‑of‑way and funding.

Council members asked detailed questions about pedestrian crossings, where additional signals or 'no right on red' restrictions might be needed, and whether the Antioch changes alone would provide meaningful improvements while the city pursues federal funding. HNTB said Antioch work would help and recommended pursuing multiple funding and partnership strategies with KDOT.

Councilmember Hans moved to accept the report; the motion was seconded and the clerk recorded a unanimous 7‑0 vote to accept the study and to pursue next steps of KDOT coordination and funding opportunities.