Wildlife Crossings Manual

The many effects of roads on plants and animals and their associated habitats have recently been sufficiently well documented to have spawned a new science: road ecology (Forman and Alexander 1998). Road ecology is an applied science that examines and documents the interactions between roads and populations of plants and animals. In its application, it seeks both to document and understand the bases of the interactions and to reconcile the need for safe and effective transportation systems with the need to effectively conserve the environment.

This Wildlife Crossings Guidance Manual (the Manual) is a literature-based guide on how to assess wildlife crossings, and includes a review of best practices to effectively mitigate road/wildlife conflicts. This Manual is intended primarily for biologists, but planners, and engineers may also find the guide useful. The manual reviews: 1) scientific publications and agency reports, 2) best practices from within and outside of California, and 3) additional sources of information to help evaluate the interface between wildlife movement and transportation corridors and to keep track of new information.

Evaluating and reducing wildlife-traffic conflicts is a concern for transportation planners, including those in the Department. Transportation agency biologists can use this Manual to help to plan projects in accordance with state and federal law, and use the information to guide recommended actions with smart planning in mind. The Manual is intended to help Caltrans staff to meet regulatory requirements and enhance efforts to avoid, minimize, or mitigate the effects of roadways on California’s plants, animals, and habitats of special concern. Facilitating wildlife crossing may help to avoid and reduce some of the effects of roadways on wildlife populations while enhancing public safety and restoring habitat connectivity.

This guidance Manual is one component of a larger Caltrans strategy to 1) catalog sources of information and knowledge about wildlife crossing, 2) generate, accumulate, and disseminate this information, and 3) develop guidelines for best practices and effective strategies to address road/wildlife conflicts.

Project Start Date: January 1, 2006

Primary Contact


The following are a list of project related resources.

Documents and Reports

  • The Wildlife Crossing Community website is an interactive manual which allows the community to comment, edit, revise or add additional information regarding wildlife crossing projects, guidance, publications, and case studies.