Crossing the Road, Raising the Bar: The ARC International Design Competition

After more than half a century of continuous road building in North America, 2 phenomena have been recognized. First, growing numbers of wildlife-vehicle collisions are leading to higher levels of personal injury and property damage and to increasing insurance premiums. With more than 4.8 million miles (7.8 million km) of roads on the continent (Central Intelligence Agency 2012), Americans have one of the highest rates of private automobile ownership on the planet; more than a quarter billion vehicles use these roads (Davis et al. 2011). Given the dominance of the road in North America, and the fact that we now spend on average 1.5 hr per day in the car (Buehler 2010) it has become disturbingly commonplace—and acceptable—for wildlife to be killed on our roads. While human mortality numbers are not large, wildlife-vehicle collisions have increased by 50% in the past 15 yr. A U.S. Federal Highway Administration study reports that there are an estimated 1 to 2 million collisions between cars and large mammals every year in the U.S. (Huijser et al. 2007), representing a significant danger to human safety and wildlife populations. Wildlife-vehicle collisions are also increasing as a proportion of the total accidents on the continent's roads, costing Americans more than U.S.$8 billion annually (Huijser et al. 2011). In addition to obvious concerns for motorist safety, there are serious implications for wildlife in terms of both population viability and habitat connectivity. Road mortality is documented as one of the major threats to the survival of 21 federally listed threatened or endangered species in the North America (ven der Ree et al. 2011).

Second, at a much larger scale, the last several decades of road building have resulted in significant habitat losses through the linked processes of habitat fragmentation and (by consequence) habitat restriction as species are limited to increasingly isolated patches in which they can live and move. Subsequent loss of gene pool diversity is a related factor that further exacerbates the problem of habitat fragmentation. More recently, research on climate change suggests many wildlife species may be forced to migrate in changing patterns across our landscapes in search of new habitats as resources become scarce in their current home ranges (Heller and Zavaleta 2009).

An emerging priority for both transportation and natural resource agencies is to make highways safer for both drivers and wildlife. One of the proven solutions to improve safety, reconnect habitats, and restore wildlife movement is the provision of wildlife crossing infrastructure at key points along transportation corridors. Throughout Europe, in Asia, Australia, and in various North American locations, wildlife crossing structures have been deployed with demonstrated success. These structures include both underpasses and overpasses, both of which have been constructed in a variety of sizes and designs. Although wildlife underpasses are less costly structures to build and more commonly used by a diversity of species, wildlife overpasses are preferred by certain wide roaming and charismatic species-at-risk, such as grizzly bears (Ursus arctos), for example. Overpass structures are also more widely recognized as they are visible and noteworthy to passing motorists. As such, wildlife overpasses present a timely opportunity for the general public to experience—and identify with—engineered landscape designs that create safer roads while protecting wildlife populations and restoring ecosystem function through improved landscape connectivity. Furthermore, lighter, flexible, and adaptive infrastructures may offer effective means to facilitate wildlife mobility and population survival under uncertain climate conditions.

In 2010, the ARC International Wildlife Crossing Infrastructure Design Competition was launched to explore new materials, new methods, and new thinking about wildlife crossing infrastructure (ARC 2010). The ARC competition engaged interdisciplinary teams of the world's leading engineers, landscape architects, and ecologists to create the next generation of wildlife crossing infrastructure for North America's roadways. Design teams were challenged to develop new solutions for animal road-crossing structures that would be cost-efficient, ecologically responsive, safe, and flexible; the teams developed concept solutions that could be readily...