Road Ecology

A nonprofit organization committed to ecological research and conservation

ECOSTUDIES INSTITUTE

ECOSTUDIES INSTITUTE

Contact Information: Ecostudies Institute P.O. Box 703 Mount Vernon, WA 98273 305-213-8829 ecostudies@ecoinst.org

Wildlife crossings: are they worth it? No aspect of road ecology has received as much attention as wildlife crossings.  Wildlife crossings can take many forms - underpasses, overpasses, warning signs, crosswalks - but the point is to allow animals to cross the road safely.  Structures that allow wildlife to cross above or below the roadway are without doubt the most effective, but debate persists as to whether the benefits of constructing and maintaining these structures justifies the cost.  A recent report by Bridget Donaldson, a research scientist at the Virginia Transportation Research Council, suggests that they do.  Examining two underpasses in Virginia, one that cost approximately $250,000 to construct and the other approximately $590,000, Donaldson found that the cheaper underpass had only to prevent 3 deer-vehicle collisions per year to pay for itself, while the more expensive had to result in 9 fewer collisions annually.  Given that she documented over 600 instances of deer using the underpasses to cross below the roadway, it is quite likely that the residents of the state of Virginia benefit economically from the existence of these wildlife crossings.   Although this analysis is not definitive, it does suggest that well-placed wildlife crossings will pay for themselves.  Indeed, Donaldson's cost-benefit analysis is quite conservative because the only cost involved is the cost of property damage to the motor vehicle ($2,530). The actual costs of each collision are likely much higher, as one must also consider the insurance costs (which are passed on to all consumers); costs associated with human injury or death, including costs of lost productivity; the economic value of the animal; and the cost of cleaning up the accident and removing the animal carcass.   A simple cost-benefit analysis also ignores the more elusive benefit that comes from reducing habitat fragmentation and maintaining viable populations of wildlife.  For a species with economic value, such as deer or elk, these benefits could be estimated based on the economic value we place on each animal (as measured by the amount of money spent hunting or observing these species), but for other species estimating the benefit of a wildlife crossing will be more challenging. In the end, however, the strongest argument for building wildlife crossings may come from the courts.  In 2003, the Court of Appeals for the State of Arizona upheld a $3.1 million verdict against the state in a case in which a motorist sued the state after colliding with a road-killed elk on Interstate 40 near Flagstaff.  The court held that the Arizona Department of Transportation "had ample notice of a dangerous condition on this portion of I-40" and that the state was negligent in failing to take additional measures to prevent elk from wandering on to the highway.  Other state courts have ruled differently in other cases, yet all of these decisions were made on much narrower grounds, and thus Booth v. State of Arizona may provide a better glimpse at the future relationship between state departments of transportation and wildlife crossings.