Proposed wildlife crossings in Jackson, Wyoming

Vehicle collisions with large mammals can result in property damage, injury and death. The Wyoming Department of Transportation (WYDOT) estimates that there is a 79-percent chance of a driver's colliding with wildlife on Wyoming roads.[4] WYDOT also estimates that these collisions result in $50 million in damage per year (vehicle damage and personal-injury costs).[5] WYDOT estimates that the average animal collision in Wyoming will cost a driver $11,600.[6] In a 2003 study by the Jackson Hole Wildlife Foundation, it was estimated that wildlife collisions in Teton County cost $1.2 million per year.[7] More recently, the Jackson Hole Wildlife Foundation completed an economic impact assessment for 2016-2017 that found total economic loss from wildlife collisions to be $3,172,837 in Teton County.[8]

The Nature Conservancy (TNC) estimates that wildlife collisions cost Wyoming drivers $25 million in injury and property damage, and $24 million to taxpayers in lost wildlife productivity. TNC also estimates that Wyoming wildlife collision costs involving mule deer, elk and moose are $10,500, $25,319, and $37,873, respectively.[9] A number of studies document the economic value of wildlife, including the major local economic drivers of tourism, recreation and hunting.[10] Studies indicate that there are approximately 211 fatalities and 29,000 human injuries in the United States each year due to vehicle collisions with wildlife.[11]

Wildlife is impacted by roads and traffic in five broad categories: loss of habitat, road mortality, barriers to wildlife movement, decreases in habitat quality, and the introduction of non-native species. These categories are used to estimate the impact of roads on biological conservation. In addition to deer, elk and moose, animals with high conservation value in the area include river otter, lynx, grizzly bear, and bison.[3] According to Anthony Clevenger of the WTI, "generalizations about the conservation value of habitat corridors remain elusive because of the species-specific nature of the problem".[12] Due to the complex nature of habitats in and around Jackson, the Teton County Wildlife Crossing Master Plan evaluates the biological conservation value of each roadway based on the migration patterns of large and medium-sized mammals most likely to encounter vehicle traffic on a specific route.[3]

The Jackson Hole Wildlife Foundation (JHWF) demonstrated the urgency of this problem by tracking moose-specific deaths due to vehicle collisions in the Jackson area. JHWF tracked 50 moose deaths due to collisions over a decade, and compared that to the estimated 70 moose that live near town. Their research indicates that this moose population could be at risk due to the frequency of collisions.[13] JHWF believes that it "can save an average of 190 moose, 210 elk and 360 deer every 20 years" with the construction of wildlife crossings.[14]

In assessing biological conservation value, the concept of ecological permeability becomes an important element of the master plan. Ecological permeability has broad scientific consensus. Although vehicle–wildlife collisions are the most acute aspect of biological conservation with respect to wildlife overpasses, the ability for species to migrate and interact with the larger ecosystem is considered crucial for the health and maintenance of species and ecosystem. Research also demonstrates that facilitating permeability requires that wildlife crossings be species-specific; for example, ungulates prefer overpasses and carnivores prefer underpasses.[15] The Teton County Master Plan takes these biological-conservation and permeability factors into account in its analysis and planning process.[3]

Studies indicate that wildlife warning signs can reduce collisions by nine to 50 percent, and Teton County has a variety of warning signs in place. Animal-detection systems that alert drivers when an animal is active in the area can reduce collisions by 33 to 97 percent.[3]

Speed limits vary along the target roads between 25 and 65 miles per hour (40 and 105 km/h), with the average speed limit 55 miles per hour (89 km/h) (variable speed limits, depending on daylight, are set along two stretches of highway).[3] Since research shows that most collisions occur at dawn and dusk, Teton County has implemented variable speed limits that decrease driving speeds at night.[16] The master plan does not recommend a general reduction in speed limits, however, due to a possible negative impact on safe highway driving.[3]

The master plan cites four studies indicating that wildlife fences are "one of the most effective and robust mitigation measures to reduce collisions with large animals."[3] Wildlife fencing can keep animals off the road and funnel them to safe crossing locations. Best practices should be used to ensure that fencing is species-specific, minimizing larger ecological impacts.[3]

There are numerous types of wildlife crossings that can be implemented in Teton County. These include overpasses, open span bridges, underpasses and pipes. Similar to wildlife fencing, the success of crossings depends on their design process and how they relate to target species. The Master Plan used existing research to make recommendations based on animal type, including six ungulate species and eight carnivore species.[3]

Multiple use structures facilitate the movement of humans and wildlife. Although the master plan evaluated their feasibility, it does not recommend them due to their potential to increase the number of vehicle-wildlife collisions.[3]