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Highway Passages for Small Terrestrial Wildlife – Summary and Repository of Design Examples

Project #: 4W7193
Start Date: 04/26/2018
End Date: 09/18/2019

There is a need to better understand how to make road crossing structures that are designed for purposes other than wildlife passage (e.g., drainage structures, bridges across streams or rivers, or livestock crossings) also suitable for small animal species. This project will review and summarize existing information on how to reduce the impacts of roads on small animal species, including terrestrial mammals, amphibians, and reptiles. The team will review plan sheets, photographs, and detailed project descriptions and summarize design criteria for structures that provide safe passage across roads, as well as barriers designed to keep these species groups off the highway and guide them towards safe passage opportunities. The team will set up a central repository with case studies and plan sheets for structures and barriers (both successful and unsuccessful) to demonstrate lessons learned in providing connectivity and reducing direct road mortality.

The results of this effort will provide transportation planners, road designers, and road builders with a synthesis of the most current information about how best to provide safe passage across roads for small animals and reduce direct road mortality. User accessibility and ease-of-use will be essential components of this synthesis. The information will allow for better and more cost-effective decision making, better compliance with state and federal environmental regulations, and increased population viability of selected small animal species in the landscape.


The two objectives of this research are to: 1. Gather and summarize existing information on road passage structures and exclusion barrier systems,
including specifications, monitoring techniques, lessons learned, and synthesize the information to identify knowledge gaps for small terrestrial mammals, reptiles, and amphibians; and 2. Develop a navigable report linked to a central repository of case studies, including plan sheets and other supporting documents for user friendly access by state DOTs.


  • Marcel Huijser
    Marcel Huijser


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