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ITD Projects Southwest Idaho U.S. 20/26 Corridor Preservation Study, Caldwell to Boise

U.S. 20/26 Corridor Preservation Study, Caldwell to Boise

An aerial view of U.S. 20/26 looking west from Eagle Road

Study Facts
Key Number: 7826
Project No.: STP3230(106)

The Idaho Transportation Department (ITD) is studying U.S. 20/26 from Aviation Way in Caldwell to Eagle Road in Boise. This study is called the U.S. 20/26 Corridor Preservation Study. The corridor study is being conducted to identify the transportation improvements needed to preserve the corridor in order to accommodate future traffic demands.

Study Background
U.S. 20/26 is one of a few east-west roadways that stretch from Caldwell to Boise and it is an important commuter route in the Treasure Valley. In 2005, ITD began this study in partnership with the Community Planning Association of Southwest Idaho (COMPASS) to plan improvements to this corridor. Land adjacent to the roadway is being developed and the future is expected to bring mixed-use development that will transform U.S. 20/26 from a rural roadway into a busy urban corridor. Over the past six years, ITD has:
  • Began an environmental review of the U.S. 20/26 corridor.
  • Conducted open houses to provide the public with an opportunity to learn about the corridor study. Stakeholders have expressed concerns, needs and provided input on a vision for the corridor and improvement options. Click here to review a summary of past comments.
  • Developed an access management plan.
  • Developed conceptual roadway designs

ITD is continuing to work with cities, counties, local highway districts and the public to keep U.S. 20/26 functioning as a safe, major east-west route.

Study Components
  • Transportation planning is an important component of this study. It allows ITD to:
    • Develop safety and congestion management strategies in the corridor area, including limiting access to the highway.
    • Identify opportunities to accommodate alternative transportation modes, such as transit, cycling and walking.
    • Identify strategies to preserve right-of-way.
    • Prioritize proposed improvements.
    • Assure consistency between the corridor plan and the land use comprehensive plans for the cities and counties.
  • ITD is working with local governments, highway districts and the public to develop the roadway design for this corridor. Based on input and analysis throughout the project, ITD proposes to widen and improve the entire corridor from Aviation Way in Caldwell to Eagle Road in Boise. The roadway’s future design considerations include:
    • Widening U.S. 20/26 to four or six lanes depending on the location.
    • Making the entire roadway a divided highway with a median in select areas.
    • Improving intersections and cross streets (i.e. add turn lanes, signals, and/or pedestrian ramps, etc.)
    • Adding bicycle and pedestrian facilities along the roadway.
  • ITD will develop a corridor plan for this project that identifies future right-of-way needs and proposed lane configurations. A corridor plan is a series of recommendations for managing and improving the transportation system within a specific corridor, based on a 20-year forecast.

  • The National Environmental Policy Act (NEPA) requires that an environmental review be completed before corridor improvements and land can be acquired with federal funds. An Environmental Assessment (EA) will be completed for the U.S. 20/26 Corridor Preservation Study that will identify impacts to:
    • Social and Economic Conditions/Environmental Justice/Land use
    • Archaeological, Cultural and historical resources/Visual Quality
    • Transportation, Noise and air quality
    • Wetlands/Wildlife, Fish and Vegetation/Threatened and Endangered Species
    • Surface Water/Floodplains/Water Quality/Groundwater/Soils
    • Hazardous Materials

Please visit: for more information on these studies.

Once complete, the Idaho Transportation Department will use the U.S. 20/26 Corridor Preservation Study to:

  • Manage and improve the transportation system within the corridor.
  • Manage access within the corridor.
  • Program, design and construct projects within the corridor as funding becomes available.

Local agencies will use the corridor study to plan and approve future development along U.S. 20/26 between Caldwell and Eagle Road. The corridor study will help coordinate new development with future road improvements and ensure adequate right-of-way remains available for road widening and other potential improvements, such as access points and sidewalks.

Transportation agencies and city planners will continue to coordinate on issues such as access management and future development as the study progresses.

Funds are currently not available to acquire land, prepare final design plans or construct any components of this project.

Contact Us
  • Adam Rush, Idaho Transportation Department, Public Involvement Coordinator,, (208) 334-8119

Make Comments

The Idaho Transportation Department values your input. Submit written comments using one of the forms below or contact for more information.
    •Email Us please include your name and address
    •Download a comment form (word doc)

Compliance with Title VI of the Civil Rights Act
The Idaho Transportation Department (ITD) is committed to compliance with Title VI of the Civil Rights Act of 1964 and all related regulations and directives. ITD assures that no person shall on the grounds of race, color, national origin, gender, age, or disability be excluded from participation in, be denied the benefits of, or be otherwise subjected to discrimination under any ITD service, program, or activity. The department also assures that every effort will be made to prevent discrimination through the impacts of its programs, policies, and activities on minority and low-income populations. In addition, the department will take reasonable steps to provide meaningful access to services for persons with Limited English Proficiency.

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ITD Public Involvement
P.O. Box 7129
Boise, ID 83707-1129
Phone: (208) 334-8119
Fax: (208) 334-8563
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Page Last Modified: 11/4/2014 7:43:41 AM

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Idaho Transportation Department
3311 W. State Street P.O. Box 7129
Boise, ID 83707-1129
(208) 334-8000