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US 20: Chester to Ashton Environmental Assessment

ITD and FHWA are initiating an Environmental Assessment (EA) to engage the public and evaluate impacts, risks, benefits, opportunities and costs associated with roadway improvements and reconstruction of US 20 between Chester and Ashton.

A public open house was held on Tuesday, June 11, from 4 to 7 p.m. at the Ashton Community Center, 925 Main Street. The displays illustrating the study process, purpose, schedule, and geography can be viewed in the Downloads and Resources. If you have questions, please reach out to the project team at or 208-870-8751.

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Purpose & Need

The purpose of the US 20 Chester to Ashton project is to enhance highway safety and operations by:
• Improving highway capacity and level of service
• Improving roadway condition
• Providing safe, efficient, and well-coordinated access to and from the highway

The need for these improvements is driven by the following:

Roadway Condition

The original road was built in 1932 and various projects have been completed to maintain its usability. However, the roadway has exceeded its design life and current conditions are rated as poor to very poor. Issues such as frost heaves, cracking, and rutting are commonplace along the corridor.



Unconsolidated accesses along the corridor increase the risk of accidents due to increased turning movements and differences in traffic speeds. Between 2013 and 2017, over 30 percent of crashes were same direction sideswipe, rear end, or angle related. As traffic volumes continue to increase, the risk of potential conflict points will also increase.


Highway Capacity & Mobility

The amount of traffic traveling the U.S. 20 corridor from Chester to Ashton has grown significantly. The current configuration does not provide for sufficient traffic flow or passing opportunities to accommodate current and future traffic volumes.

US 20: Chester to Ashton EA Timeline

Public Involvement

•  ITD is evaluating current and future traffic volumes, safety data, and other conditions in the area to develop improvements that address the purpose and need of the project.

•  A key part of ITD’s evaluation is the identification of issues and concerns important to the public. Throughout project development, ITD will solicit feedback from the public on needs along the corridor.

•  Alternatives developed will also be presented to the public and documented through the National Environmental Policy Act (NEPA) process.

Downloads & Resources

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