Improving Light and Soundscapes for Wildlife Use of Highway Crossing Structures

Research Team: Fraser Shilling (lead), David Waetjen, Travis Longcore, Winston Vickers, Sean McDowell, Adetayo Oke, Aaron Bass, and Clark Stevens

UC Campus(es): UC Davis

Problem Statement: Transportation and other agencies and organizations are increasingly planning and building under- and over-crossing structures for wildlife to traverse busy highways. However, if wildlife do not use these structures due to noise, light, and other factors, then the structures may have a low benefit to cost ratio. Several criteria are key for their success— sufficient safety and/or conservation need, cost, location, and anticipated use by wildlife. There is limited information in wildlife-crossing guidance on how wildlife biologists should advise designers, engineers, and architects on the use of structural and vegetation elements that could reduce noise and light disturbances. Although transportation agency biologists are aware of the potential for traffic noise and light to impede crossing structure use by wildlife, few tools are available to inform their advice to designers, engineers, architects, and habitat designers of the structural and vegetation elements that could reduce disturbance. Each structure represents a significant investment in time, money, and effort. If wildlife freely approach and enter these structures, the expected benefits from these costs are increased, including safer wildlife movement across the right-of-way and increased driver safety. If wildlife are hesitant to or refuse to approach structures due to noise, light, and other factors, then the structures have a much lower benefit to cost ratio.

Project Description: To address this problem, this study used field measurements and modeling of light and noise from traffic to inform and test the designs of two wildlife overcrossings. Wildlife-responsive designs were developed and tested for two crossings being considered or planned by California Department of Transportation in California. For the planned crossing of US 101 near the city of Agoura Hills (the Wallis-Annenberg crossing), the three designs consisted of noise/glare barriers; noise/glare barriers + berm; and noise/glare barriers + multiple berms. For the potential crossing of Interstate 15 south of Temecula, one design used noise/glare barriers of 3 different heights and the other had no barriers. Key limitations and opportunities for each design approach were identified. Creating “dark and quiet paths” using a combination of berms and noise/glare barriers could decrease disturbance in the crossing structure approach zones and increase the wildlife-responsiveness of the designs.

Status: Completed

Budget: $79,800

Project Partner(s): California Department of Transportation, Resource Conservation District Santa Monica Mountains

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