The Idaho Transportation Department announced Thursday a $42 million expansion project for Highway 20-26 between Caldwell and Nampa, transforming the heavily congested corridor into a divided four-lane highway with dedicated turn lanes, improved intersections, and a multi-use path connecting the two largest cities in Canyon County. The project addresses what ITD identifies as the most dangerous and congested non-interstate road segment in southwestern Idaho, carrying over 28,000 vehicles daily through a stretch originally designed for fewer than 15,000.
Highway 20-26 serves as the primary east-west artery connecting Caldwell and Nampa and carries the daily commutes of thousands of Canyon County workers who travel between the two cities and onward to employment centers in Ada County. The corridor has experienced a significant increase in serious-injury and fatal crashes over the past five years, with ITD recording 47 injury crashes and 4 fatalities in the project area during 2025 alone.
What the Highway Expansion Includes
The project will widen the existing two-lane highway to four lanes with a raised center median from Caldwell’s eastern city limits to Nampa’s western boundary — approximately 8 miles. Six major intersections will receive dedicated left-turn lanes and traffic signals, replacing the current two-way stop configurations that create dangerous cross-traffic movements. A 10-foot-wide paved multi-use path will run alongside the highway’s south side, providing a safe bicycle and pedestrian connection between Caldwell and Nampa for the first time.
ITD District 3 engineer Blake Rindlisbacher said the project was designed to accommodate Canyon County’s projected growth through 2045. “This corridor is going to see traffic volumes double or triple over the next 20 years as Canyon County continues to grow,” Rindlisbacher said. “Building it right now, with capacity for the future, is far more cost-effective than trying to patch and expand a road that’s already failing.”
Funding and Construction Timeline
The $42 million project is funded through federal highway funds ($28 million), state highway distribution funds ($10 million), and local match contributions from Canyon County and the cities of Nampa and Caldwell ($4 million combined). Construction begins in spring 2027 with completion expected in late 2028. During construction, the highway will remain open with reduced lanes and temporary traffic signals.
ITD will coordinate with the Canyon County Highway District and local emergency services to maintain access to homes, businesses, and farms along the corridor throughout construction. Agricultural operations with equipment access needs will receive advance notification of any temporary closures.
Impact on Canyon County Commuters and Businesses
The expansion will significantly reduce commute times and improve safety for the thousands of Canyon County residents who drive Highway 20-26 daily. Current peak-hour congestion adds 15-20 minutes to the Caldwell-Nampa trip; the expanded highway is projected to reduce travel times to 12-15 minutes even at anticipated future traffic levels. Improved access and visibility will also benefit the commercial businesses along the corridor, including agricultural supply companies, equipment dealers, and retail operations.
What Comes Next
ITD will host public open houses in Caldwell (April 10) and Nampa (April 12) to present final design plans and answer questions about construction impacts. Commuters can sign up for construction alerts at itd.idaho.gov/d3. Canyon County residents with questions about property access during construction can contact ITD’s community liaison at 208-334-8300. For statewide transportation coverage, visit Idaho News.