UDOT advances Center Street as preferred I‑15/Spanish Fork interchange after screening alternatives

On March 20, 2024, Utah Department of Transportation project manager Darren Bunker told the Utah County Commission that, after two rounds of screening, UDOT is advancing a Center Street interchange concept for the proposed I‑15/Spanish Fork interchange.

Bunker said the study evaluated five initial concepts — at 400 North, Center Street, 100 South, 900 South and a split interchange — against the project's three goals: regional mobility (direct access to I‑15), safe multimodal connections to a planned transit facility, and improved local mobility on Spanish Fork Main Street. He described a two‑stage process: a level‑1 high‑level screening to test basic effectiveness, followed by level‑2 analysis of environmental and regulatory impacts.

"We have selected this concept to move forward to that more detailed design," Bunker said, summarizing UDOT's decision to carry the Center Street option into further engineering. He told commissioners the Center Street option had the fewest residential relocations and the lowest impacts to aquatic and to the properties protected under "section 4 f," which UDOT identified as historic sites and certain park or resource areas.

UDOT presented comparative figures used in the screening: the 400 North option would have attracted roughly 38,000 vehicles in their analysis while the split interchange would have attracted about 56,000; the 100 South concept would have required substantial property acquisition and relocation (UDOT cited 39 full acquisitions, 33 relocations and impacts to more than 90 properties at that location) and higher impacts to archaeological sites. Despite stronger traffic performance for the split interchange, Bunker said its impacts to resources governed by "section 4 f" made it infeasible at this stage.

The agency said it would refine design work on drainage, hydraulics, pedestrian and bicycle accommodations and local access in the coming months and expects to select a preferred alternative in the spring, approximately May. After that selection, UDOT plans a 30‑day public comment period and will respond to comments collected during the environmental process.

Bunker also noted that separate, but related, transit planning for the FrontRunner South project could affect vehicle access decisions at 100 South. He said UDOT is coordinating with the South Valley transit team and examining options to preserve farm access and the farmers' market on Center Street where possible, while still providing safer crossings for pedestrians and bicyclists (including the possibility of retaining 100 South for farm vehicles but rerouting pedestrian/bicycle traffic under I‑15).

UDOT provided the commission with a fact sheet and contact information for the study team and encouraged public engagement during the comment period.

Next steps: UDOT anticipates completing the detailed analysis by spring and making a preferred‑alternative selection in May, with a 30‑day public comment period to follow.