US 36 Wildlife Crossings
A large group of elk cross US 36 with cars stopped on the highway

US 36 Wildlife Crossings

Boulder County is in the process of planning wildlife crossing structures along US 36 between Boulder and Lyons. These structures help reduce collisions between vehicles and wildlife, and make it easier for animals to move around the area. The project is still in its early planning phases and public input, including input from nearby property owners, will be requested and used as the project progresses.

Action Needed

Reducing the number of vehicle-related wildlife accidents on US 36 between Boulder and Lyons has been a longstanding priority. This was further affirmed by the Eastern Slope and Plains Wildlife Prioritization Study (ESPWPS) in April 2022. The report was conducted for the Colorado Department of Transportation and Colorado Parks and Wildlife and outlines regional priorities and recommended actions aimed at decreasing wildlife-vehicle collisions.

Top 5%

The section of US 36 between Boulder and Lyons (emphasis on Nelson to St. Vrain) was rated in the top 5% and has the highest prioritization score in Region 4. This is based on modeling that includes wildlife-vehicle collisions, deer/elk density of winter range use, deer/elk migration routes, traffic volumes overall, and distance from suburban housing density.

10x Higher

Wildlife strikes average 3.2 animals per mile/per year which is more than 10 times higher than the rest of Boulder County, which averages .26 strikes per mile/per year.


The human cost of wildlife collisions is significant. Each accident typically costs drivers $11,100 in property damages and over $101,000 if injured.

Crash Data

Traffic crash data from 2009-2018 shows wildlife-vehicle collisions are most numerous on US 36 between Boulder and Lyons.

Map showing all wildlife crashes in unincorporated Boulder County by Animal Hit (2009-18)

Map showing all wildlife crashes in unincorporated Boulder County by severity (2009-18)

Wildlife Crossings

Boulder County is considering several different wildlife crossing structures including overpasses, underpasses, and wildlife fencing. The exact designs have not been finalized and below are examples of structures being considered.

A moose uses a wildlife overpass

Example of an overpass structure that allows wildlife to safely cross over a road.

Wildlife underpass structure

Example of an underpass structure that allows wildlife to safely cross under a road.

Potential Locations

  • All highway segments ranked in the top 5% of the ESPWPS were further assessed in person.
  • Consultants examined the surrounding topography to identify suitable locations for wildlife crossings and assessed whether existing infrastructure could be modified to accommodate these crossings.
  • Six areas were identified as potential wildlife crossings and one existing structure could be improved.
  • Page 232 of the ESPWPS appendix provides further details about the recommendations.

Map showing six potential spots for wildlife crossings and one existing structure that could be improved

North Foothills Bikeway Feasibility Study

Motor vehicles and bicyclists on US 36 north of Boulder

The North Foothills Bikeway Feasibility Study is underway to determine the feasibility of a bikeway along US 36. This study aims to determine the viability of constructing a dedicated bikeway that would be physically separated from motorized traffic.

Planners are collaborating closely to ensure any proposed bikeway and wildlife crossings are properly coordinated. The designs for both projects will be carefully aligned to accommodate the needs of the other, so that the implementation of one will not adversely impact the other.

By aligning these parallel initiatives, the project teams are working to deliver infrastructure solutions that safely and effectively meet the multifaceted needs of the community and improve wildlife connectivity.

Upcoming Public Meetings

May 15 at 6 p.m. – Society for Ecological: Wildlife Crossings, Habitat Connectivity, and Real World Projects
Join Society for Ecological Restoration-Rocky Mountain’s group of restoration-minded professionals for a panel discussion about all things wildlife crossing and the importance of implementing these projects from wildlife connectivity and transportation safety perspectives.


Additional meetings will be scheduled soon to provide updated information and to gather public feedback.

Previous Public Meetings

April 25 – Parks & Open Space Advisory Committee
Staff introduced the project to the Parks & Open Space Advisory Committee.
Staff Memo

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Grant funding will be essential for the completion of the project. Boulder County will actively pursue various federal and state grant programs to secure the necessary funding.

  • Wildlife Crossings Pilot Program: Established under the Infrastructure Investment and Jobs Act to provide grants for projects that seek to reduce the number of wildlife-vehicle collisions and improve habitat connectivity for terrestrial and aquatic species.
  • America the Beautiful Grant: The National Fish and Wildlife Foundation (NFWF) provides grants aimed at the development of large-scale, locally led projects spanning public and private lands. Priorities include connecting and reconnecting wildlife corridors, large landscapes, watersheds, and seascapes.
  • The Wildlife Crossing Fund: Recently partnered with private and public entities to secure $500 million dollars towards wildlife crossings
  • Safe Crossings for Colorado Wildlife and Motorists Act-SB22-151: Provides $5 million from the state’s general fund specifically towards leveraging match for the FHWA WCPP Grant.

Parks & Open Space has allocated $150,000 from Capital and Stewardship Funds to support future wildlife crossings projects. This funding will serve as matching funds for design and/or implementation efforts.

Partner Support

The project has the support of the following agencies:

  • Colorado Parks and Wildlife
  • Colorado Department of Transportation
  • Local municipalities

Contact Us

Parks & Open Space

Susan Spaulding
Environmental Resources Specialist