US-20 Ashton to SH-87 JC

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Thank you for your interest in US-20 Ashton to SH-87 JCT study. The Idaho Transportation Department is hosting Community Meetings focused on the following stretches of US-20:

Island Park Village to SH-87
August 17 from 5 p.m. – 7 p.m.
Island Park EMS Building
4378 County Circle
Island Park, ID 83429

Last Chance to Island Park Village
August 22 from 5 p.m. – 7 p.m.
Springhill Suites by Marriott
4292 North Highway 20
Island Park, ID 83429

Ashton to Last Chance
August 29 from 5 p.m. – 7 p.m.
Ashton Community Center and Library
925 Main Street
Ashton, ID 83420

This online version of those meetings will share the same information but cover the entire corridor. Please review the content and submit your comments by September 8, 2023.

Project logo.

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How to Navigate:

  • Click on the arrows on the bottom left and right side of your screen
  • Use the navigation menu at the left of the screen to revisit any part of the meeting
  • The pages are intended to be viewed in order to provide information about the study. However, you may use the tabs on the left side of the page to select any page

How to Participate:

  • Click through the slides to learn more about the project
  • Comments
    • Provide your comments at any time by clicking the “ COMMENT" button at the top right of the screen.
    • You can close the form to continue through the slides. Please make sure to hit the “Submit” button to confirm that your comment is sent to the project team.
  • The entire session should take less than 15 minutes to complete.

Project Background

With growth in traffic and tourism, ITD is working with agencies and the public to find a solution to address safety and traffic concerns on US-20 between Ashton and the junction with SH-87. ITD is seeking a solution that will handle increased traffic, meet driver expectations, and improve safety.

Map of the project area highlighted. Project beginning near Ashton and Ending at SH-87.

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Planning Process

Next Steps

A schedule of the process next steps. For detailed information, contact Brenda Elordi at the email,

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Community Impact Assessment

ITD is conducting an initial Community Impact Assessment to evaluate existing community and economic conditions from a high-level planning perspective. A detailed analysis will be conducted in the future during the National Environmental Policy Act (NEPA) phase. Topics to be evaluated are:

Property damage icon. Land Use
Property damage icon. Community Characteristics
Property damage icon. Utilities and Emergency Services
Property damage icon. Economic Conditions

How does US-20 function now?

Property damage icon. Increasing congestion is contributing to traffic crashes in the area.

Here’s what the traffic data says:

20-year traffic volume from 2002 to 2021. According to the graphic, July has the highest traffic volume increase from 6,038 vehicles in 2002, to 10,534 vehicles in 2021
Heat map of crashes along project area corridor with densest areas at the SH-47 intersection and the Federal Hill area.

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Since 2021, ITD and the Federal Highway Administration (FHWA) have been working with the public, elected officials and agencies to look at options for improvement safety and reducing congestion on US-20.

ITD anticipates incorporating recommendations made as part of this planning study into future NEPA studies, per Title 23 of the US Code, Part 168.

For more information, view the Level 1, Level 2, Level 3, and Multi-Use Crossing maps. If asked to sign in, please hit cancel and you will be entered into the site.

Screening consists of evaluating each alternative against set criteria such as:

  1. Access Management
  2. Environmental Resources
  3. Constructability
  4. Mobility
  5. Traffic Operations
  6. Safety

Alternatives that don't meet the criteria or have fatal flaws are eliminated. Alternatives needing refinement are modified to reflect stakeholder and agency suggestions or regulatory requirements.

ITD is seeking input on the Level 3b alternatives.

Check icon Indicates Alternative Advances

X icon Indicates Alternative Does Not Advance


For a more detailed look, view the AC2 video and AC3 video.

X icon AC1 (AG) - Four Lane Road Layout

Map of Ashton alternatives AC1.

Check icon AC2 (AG & GS) - Four Lane Road Layout

Map of Ashton alternatives AC2.

Check icon AC3 (AG & GS) - Four Lane Road Layout

Map of Ashton alternatives AC3.
Legend of elements found in the Ashton alternative maps.

Alternating Passing Lanes

What are Alternating Passing Lanes, or Two Plus One Highway?

An alternating passing lane or two plus one highway has alternating passing lanes added to a two-lane highway to allow drivers to pass slower vehicles. The passing lane alternates from one direction of travel to the other within a section of roadway allowing passing opportunities in both directions. A two plus one project can be introduced on an existing two-lane roadway where there is a significant amount of slow moving traffic, limited sight distance for passing, and/or traffic congestion that could be alleviated if motorists had the ability to pass slower vehicles on a more frequent basis.

Alternating Passing Lanes has several challenges including increased close calls and crashes at transition points.

Corridor Length = 45.3 Miles

Existing Passing Lanes
Northbound (NB) = 10.9 Miles
Southbound (SB) = 5.1 Miles

Map of possible and existing passing lanes along US-20.

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Design Alternatives

Challenges: Head-on perception

Graphic of alternating passing lanes along the inside lanes.

Challenges: Crown location for snowplows, keeping slower traffic to the right, merging left

Graphic of alternating passing lanes along the outside lanes.

Passing Lane Attributes

1.5–2.0 Mile Preferred

Graphic of alternating passing lanes along the outside lanes.

Note: Driveway access and approach integration in this configuration is based on IDAPA Standards.

Graphic of alternating passing lanes along the inside lanes. with a buffer area of 730 feet between transitions.

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For a more detailed look, view the Alternating Passing Lanes video

At-Grade Intersection/ Alternating Passing Lane Intersection

At-Grade Intersection

Detailed graphic of an at-grade intersection.

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  • The wider median gives drivers a refuge so they can wait to turn safely
  • Provides space to accelerate and decelerate
  • Separates turning and through traffic


  • Potentially increases the possibility of intersection crashes

For a more detailed look, view the At-Grade Intersection video

Alternating Passing Lane Intersection without acceleration or deceleration lanes

Detailed graphic of a grade-separated interchange.

Click image to enlarge


  • Allows for designated left-turn lanes on highway


  • Through traffic is reduced to a single lane in each direction at intersections
  • Adding right-turning lanes would require wider highway
  • Passing lanes must merge lanes before reaching the intersection

Multi-Use Crossings

ITD is evaluating:

  • Multi-use crossing opportunities at trails, pathways, and bridge locations that intersect US-20
    • Cyclists
    • Pedestrians
    • Snowmobilers
    • ATV/UTV riders
    • Equestrians
    • Snowshoers
    • Fishermen and other sportsmen
    • Hikers and other trail users
  • Wildlife crossing infrastructure
    • ITD is evaluating movement and wildlife migration information. Technical assistance is being provided by the U.S. Forest Service, U.S. Fish and Wildlife Service, and Idaho Fish and Game.
Photograph of pedestrian and bike trail at the side of a creek, both passing under a bridge. Below is a detailed graphic of the US-20 Highway bridge crossing a river with a wildlife bench, multi-use trail/path and the hight of the space under the bridge yet to be determined.

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DRAFT Project Purpose and Need

DRAFT Project Purpose and Need

The Ashton to SH-87 Junction section of US-20 was originally built in the 1950s. The current roadway does not provide sufficient traffic flow or passing opportunities to accommodate growing traffic volumes. The roadway has exceeded its service life and requires improvements to roadway and drainage features. Reconstruction will provide the opportunity to include design elements that reduce the severity and frequency of crashes.


The purpose of the US-20; Ashton to SH-87 Junction project is to enhance highway safety and operations by:

  • Improving access management
  • Improving regional freight movement
  • Decreasing severe crashes


The need for improvements to the US-20 corridor is to:

  • Address existing deficiencies, such as:
    • Travel time
    • Congestion
    • Delays
    • Safety
  • Prepare for future growth, economic development and tourism in the region
  • Address freight mobility


When consulting with the public and resource agencies, ITD identified additional goals to be considered as the project is developed:

  • Provide traffic calming measures or separation where the US-20 alignment runs through developed areas
  • Provide multiuse solutions that provide a range of options for recreational users
  • Integrate wildlife movement strategies in the corridor

Environmental Considerations/11 Criteria

Alternatives will be evaluated through a screening process to determine how well they meet the project’s draft purpose and need. The screening process includes evaluating each alternative based on the following 11 environmental criteria.

  1. Visual Resources
  2. Agricultural and Forest Resources
  3. Air Quality
  4. Biological Resources
  5. Cultural Resources
  6. Geology and Soils
  7. Hazards and Hazardous Materials
  8. Hydrology and Water Quality
  9. Land use and Transportation Planning
  10. Noise
  11. Social and Economic Resources

Stay Involved

Please share ideas about the alternatives shown tonight and potential design elements for a future US-20. Public input is an important part of the decision-making process.

For more information, visit the project page.


If you have questions please contact the project team.

Use the comment button at the top right of this meeting to view the comment form where you can submit comments. You can also submit comments via email to
or mail them to:

ITD District 6 C/O Brenda Elordi
206 N. Yellowstone Highway
Rigby, ID 83442

While your comments are always welcome, they can be best utilized if received by September 8, 2023.

Close comment form

While your comments are always welcome, they can be best utilized if received by September 8, 2023.