Overview
US-20 is a valuable lifeline route across east Idaho. The corridor west of Idaho Falls is needing substantial improvements to continue safely and effectively serving travelers and commuters. This project will develop preliminary design plans for reconstructing the aging US-20 roadway and determining how future passing lanes may be implemented to enhance safety along the route.
Need for this Project
The existing roadway, originally constructed in 1950, has surpassed its service life. In addition, the roadway foundation is failing, and routine maintenance treatments are becoming less effective. Reconstructing this part of US-20 is needed to ensure it can continue serving as a safe route for motorists.
This area of the US-20 corridor is located in Butte, Bingham, and Bonneville counties. It serves as the primary route to access the INL and the city of Arco, and is a popular east/west route between Mountain Home and Idaho Falls. The 60-mile stretch sees many diverse users, including snowplows, farming equipment, buses, motorhomes, trailers, and more.
This project will evaluate turning US-20 into a four-lane highway. Adding passing lanes will increase safety by improving traffic flow and providing safe passing opportunities.
What This Project Includes
Community Involvement
Community involvement is important to ITD and to the success of this project. ITD is coordinating with many local city and county officials, and several local agencies about the project, including the INL, Department of Energy (DOE), Department of Defense (DOD), and Bureau of Land Management (BLM).
In addition, ITD will communicate with the public through a variety of channels and provide opportunities for community members to give input on the project. ITD hosted a public meeting for community members to learn about the project in September 2025:
- 47 people attended in person, 160 viewed online
- 25 total comments were received
- Postcard invitation sent in advance to 7,200 homes
- Comments largely expressed support and approval for this project
- Some recommended improvements specifically to the “Puzzle• junction
- Others offered specific design consideration input such as providing and/or improving access roads; making accommodations for farm equipment; reconsidering locations of some turnaround areas; and accounting or wildlife in the area
As a result of this public feedback, alterations to some turnarounds and access points have been made through the design process since. A future project to improve the Puzzle is currently programmed for the year 2031 and feedback will be integrated once design phase in underway there.
To view information from this September 2025 meeting, please click here.
Turnaround Access
ITD has received and addressed multiple questions about access to the Idaho Falls Speedway at Noise Park off of US-20. Feedback was used in working with the City of Idaho Falls and Idaho National Guard, the property owners at this turnaround.
Timeline
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2024
- Established parameters of project
- Began early environmental and technical work
- Reached out to local agencies and stakeholders
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Spring 2025
- Continued environmental and technical work
- Evaluated design alternatives
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Summer 2025
- Met with property owners
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Fall 2025
- Finalized preliminary design plans and environmental and technical work
- Hosted public meeting
-
2026
- Construction could possibly begin dependent on funding.
Project schedule may change as more data and information is gathered.
Frequently Asked Questions
With a four-lane divided highway, US-20 west of Idaho Falls will look and operate more like the route from Idaho Falls to Rexburg, minus interchange exits. In order to ensure safety of at-grade intersections, motorists will need to access a turnaround location in order to cross the highway or turn left. Decelerations lanes will be included at each turnaround location and will be approximately 700 feet long. This will allow traffic to safely slow down before getting into the turnaround area. Motorists will then stop at the stop line until it is safe to proceed forward or turn left. The turnaround areas will be big enough for farm vehicles and semi-trucks to safely wait in without impeding traffic.
Proposed turnaround areas are located at:
ITD has coordinated with property owners, emergency responders and agencies, such as the City of Idaho Falls, Idaho National Laboratory, Bureau of Land Management, and Idaho Military throughout this project.
Each proposed turnaround location was selected based on safety data, traffic counts, and other factors:
- Large turning movements found in the traffic study (particularly at 105th W, 135th W, the INL Materials and Fuels Complex entrance at Taylor Blvd, and the INL Reactor Site entrance at Fillmore Blvd)
- Agricultural access (such as at 155th W and MP 285.2)
- Future development plans (such as at MP 299.7 and 288)
- Preferred two to three mile spacing between turnaround locations (between 65th W and MP 291) for safety
Many community members and local leaders have shown an interest in improvements to the US-26/US-20 Junction. Based on this feedback, ITD has added a future project to improve the Puzzle, currently programmed for 2031 depending on funding. ITD will gather public input and feedback to begin designing improvement plans as that project gets closer.
ITD has already received interest from several contractors on this project. Construction will include building several miles of four-lane divided highway, reclaiming old lanes, constructing turnaround areas and rock excavation. ITD anticipates this will take two construction seasons to complete.
One of the key benefits of the project design is that traffic will be essentially uninterrupted as the new roadways are being built. During construction, traffic will continue to use the existing US-20 lanes while two new lanes are built. Then, traffic will use the new lanes while the old lanes are reconstructed.
Construction on this project is being split up into 10-mile sections for funding and constructability purposes.
Downloads & Resources
Contact Information: gregg.bowman@itd.idaho.gov