Caltrans integrates both fish and wildlife considerations into the design of their state highway structures to improve habitat connectivity for native fish and wildlife species. Crossing features, such as animal detection and driver warning systems, undercrossings provided by span bridges, overpasses that create land bridges, and wildlife exclusion and lateral escape measures, greatly enhance wildlife connectivity and survivability along the state highway system. Best practices for multi-purpose design include early coordination with stakeholders, assessing existing water conveyance features, incorporating maintenance measures to keep passageways clear and unobstructed, and making smart use of fencing to ensure additional barriers to movement are not created. The result of sound planning, design and implementation is a suite of aquatic and terrestrial species that benefit from connected ecosystems, and safer drivers that have fewer wildlife-vehicle encounters.

  • Addressing terrestrial wildlife connectivity can and should be incorporated as part of fish passage solutions/design through full span structures.

  • Taxa-specific solutions are not as successful nor as effective as solutions that provide passage/porosity for a suite of species.

  • Leveraging terrestrial connectivity considerations with fish passage connectivity solutions will result in the most significant benefits to native fish and wildlife than addressing either terrestrial or aquatic connectivity issues in isolation and will result in long-term cost savings for conservation restoration and enhancement activities.

  • California has an opportunity to serve as a nationwide model by implementing a coordinated, comprehensive, multi-taxa approach to enhancing connectivity along the state highway system, which could result in other California management agencies using similar solutions on their transportation corridors.

Guidance for Successful Fish and Wildlife Connectivity Projects

Successful fish and wildlife connectivity projects require adequate planning and continuous staff support to achieve desired goals. The six steps in the process include:

  • Using science and data to inform barrier locations with the greatest biological value.

  • Selecting the proper engineering solution after considering a variety of alternatives that maximize return on investment.

  • Obtaining adequate funding to permit, construct, and monitor the site post-construction.

  • Ensuring appropriate permits are acquired to construct the project.

  • Constructing the project.

  • Evaluating the success of the project design in meeting connectivity goals.



Fund priority locations



Implement project



Successful design performance


Successful connectivity and environmental enhancement projects are often arduous and require support from many disciplines and agencies. These steps ensure that scientists, engineers, and advocates focus on properly identifying priorities, and improving outcomes and return on the limited available funding.

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