…By Reconciling Mobility

1,569 total words    

6 minutes of reading

A road is a thoroughfare designed to connect two places—a route to link communities. Virtually every definition of “road” implies connectivity. Yet the unintended consequence of centuries of road building has been to divide as much as to connect. Perhaps we ought to revisit the road.

In the last sixty years, the number of cars in the United States has increased more than threefold[1] and settlements have sprawled out from urban centers in unprecedented growth: roads have fragmented our landscapes, divided habitats, and grown ever more congested. Today, new roads are often built for the primary—but misguided—intention to alleviate congestion. Yet it’s clear that more routes lead to more traffic, and inevitably to further fragmentation.[2] Divided habitat and severed landscapes degrade both nature and culture: not least, the wildlife among us.

Today, there are more than 4.8 million miles (7.8 million km) of roads on the continent.[3] Americans have one of the highest rates of private automobile ownership on the planet, with more than a quarter billion vehicles using these roads.[4] Given the dominance of the road in North America and the fact that we now spend on average 1.5 hours per day in the car,[5] it has become disturbingly commonplace—even acceptable—for wildlife to be killed on our roads. Collisions between wildlife and vehicles have increased by 50 percent in the past fifteen years. These accidents now cost Americans a staggering $8 billion every year.[6]

The prevalence of roadkill is both an obvious and disturbing result of the conflict between the needs of humans and animals. The human need to get to where we are going safely and quickly is a basic expectation of modern society. Yet wild animals need connected landscapes: they must cross our roads in search of food, mates, and shelter. Our expanding network of roads, highways, and interchanges criss-crosses the continent, interrupting and disconnecting our landscapes—and with it, the territories of wild animals. Many in the most basic quest for survival are routinely struck and killed by vehicles.

But this is not merely a wilderness or rural issue—it is a problem that affects everyone; those of us living and driving in busy suburban and urbanizing landscapes are more likely to witness or experience the conflicts firsthand.[7] In fact, growing numbers of wildlife-vehicle collisions are leading to higher levels of personal injury and property damage, and with this, rising insurance premiums. While human deaths are not high compared with other accidents, wildlife-vehicle collisions have increased significantly. A recent U.S. Federal Highway Administration study[8] reports that there are approximately one to two million collisions between cars and large mammals every year in the United States. This represents a significant danger to human safety and to wildlife populations. Wildlife-vehicle collisions are also increasing as a proportion of the total accidents on the continent’s roads.[9] Even if not physically hurt or economically affected by a collision, many people report feeling traumatized after hitting an animal.[10]

The TransCanada and the Canadian Pacific Railroad in the Bow River ValleyAlongside these obvious concerns for motorist safety are serious implications for wildlife. Road mortality is documented as one of the major threats to the survival of twenty-one federally listed threatened or endangered species in North America.[11] On a much larger scale, conventional road building results in significant losses of habitat for wild animals. Road networks carve up our landscapes into small, isolated patches in which wildlife must live and move, faced with declining genetic fitness as populations become separated. Worse yet, basic wildlife mobility often conflicts with major transportation routes. Most of North America’s major highways cross the continent in an east-west orientation, but wildlife movement patterns tend to flow north-south following mountain topography, such as the Rockies, the Appalachians, and the coastal ranges. These landforms have always been important habitat and migration corridors, and they may become still more significant. 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.[12]

But roadkill is not simply “bad luck” or an unfortunate consequence of driving; it’s an avoidable cost and a preventable loss. If we rethink our mobility to understand that both humans and wildlife share a common need to move, we can redesign the road to provide safe passage for all.

Indeed, an emerging priority for transportation and natural resource agencies is to make highways safer for both drivers and wildlife. One of the proven solutions is to build wildlife crossing structures.[13] When designed and implemented strategically, wildlife crossing structures can radically reduce the number of collisions to save costs and, most significantly, human and animal lives. Better still would be to redesign our transportation infrastructure to include a network of wildlife-crossing overpasses and underpasses along all key migration corridors.

This is not a new idea. Providing crossing infrastructure at key points along transportation corridors is known to improve safety, reconnect habitats, and restore wildlife movement. Throughout Europe, Asia, Australia, and North America, hundreds of crossing structures have already been implemented with demonstrable success.[14] These include underpasses and overpasses that have been constructed in a variety of sizes and designs. Although wildlife underpasses are less costly to build and more commonly used by a diversity of species, wildlife overpasses are preferred by certain wide-roaming and iconic species at risk, such as grizzly bears. Overpass structures are also more visible and noteworthy to motorists.

In 2010, the ARC International Wildlife Crossing Infrastructure Design Competition[15] engaged the world’s leading engineers, landscape architects, and ecologists to create the next generation of wildlife crossing infrastructure for North America’s roadways. Designers were challenged to develop new solutions for animal road-crossing structures that would be cost-efficient, ecologically responsive, safe, and flexible; they developed concept solutions that could be readily adapted for widespread use in various locations and under many conditions, including climate change. The resulting schemes made considerable progress toward the (re)design of highways to maintain the integrity and connectivity of our ecosystems, reduce the carbon footprint, minimize the consumption of non-renewable materials, recycle resources, and extend the life cycle of transportation infrastructure—all while providing safe and efficient mobility for humans and wildlife.

By redesigning the road for two “clients”—animal and human—wildlife crossing infrastructure presents a timely opportunity to communicate both the problem and the solution to the public. In building crossing structures that are visible and legible, we may empower motorists to experience engineered landscape designs that create safer roads, while simultaneously demonstrating the importance of (re)connected landscapes. Widespread deployment of this relatively simple redesign tactic may change the way we move and live.

We have proven solutions to reweave our landscapes, protect our wildlife populations and their habitats, and ultimately restore the essential functions of North America’s wild ecosystems. In rethinking mobility and redesigning the road for safe passage for all, we honor the landscapes that sustain us and the places we call home. It’s time to redesign the road.

[1] U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics 2011, National Transportation Statistics, table 1-11,

[2] The problem of habitat fragmentation by roads is well documented in both the scholarly literature and popular media. See, for example, J.P. Beckmann, A.P. Clevenger, M.P. Huijser, and J.A. Hilty, Safe Passages: Highways, Wildlife and Habitat Connectivity. (Washington, D.C.: Island Press, 2010). See also Eric Bendick’s documentary film, Division Street, 2009, at; and an interactive online documentary, Bear71, 2012, by Leanne Allison and Jason Mendes, at

[3] Central Intelligence Agency, The World Factbook, 2012,

[4] S.C. Davis, S.W. Diegel, and R.G. Boundy, Transportation Energy Data Book: Edition 30, U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, June 2011, Table 3.5, pp. 3-9.,

[5] See also R. Buehler, “Transport Policies, Automobile Use, and Sustainable Transportation: A Comparison of Germany and the USA,” Journal of Planning Education and Research 30 (2010): 76-93, DOI: 10.1177/0739456X10366302,

[6] M.P. Huijser, J.W. Duffield, A.P. Clevenger, et al., “Cost-Benefit Analyses of Mitigation Measures Aimed at Reducing Collisions with Large Ungulates in the United States and Canada: A Decision Support Tool,” Ecology and Society 14, no. 2 (2011): 15,

[7] Residents of the northeastern states, particularly West Virginia (1:53) and Pennsylvania (1:86), have the highest risk of collision with deer, according to 2011 data collected by State Farm Insurance,

[8] M.P. Huijser, P. McGowen, J. Fuller, et al., Wildlife-Vehicle Collision Reduction Study. Report to Congress, 2007, by the U.S. Department of Transportation Federal Highway Administration, Washington D.C.

[9] Beckmann, Clevenger, Huijser, and Hilty, Safe Passages.

[10] See, for example, and

[11] R. Van der Ree, J.A.G. Jaeger, E. van der Grift, and A.P. Clevenger, “Effects of Roads and Traffic on Wildlife Populations and Landscape Function: Road Ecology is Moving toward Larger Scales,” Ecology and Society 16, no. 1 (2011): 48,

[12] N.E. Heller and E.A. Zavaleta, “Biodiversity Management in the Face of Climate Change: A Review of 22 Years of Recommendations,” Biological Conservation 142 (2009): 14-32.

[13] A.P. Clevenger and M.P. Huijser, Wildlife Crossing Structure Handbook: Design and Evaluation in North America (Lakewood, CO: U.S. Federal Highway Administration, 2011), pub. no. FHWA-CFL/TD-11-003,

[14] See, for example, L. Tepper, “Road Ecology: Wildlife Habitat and Highway Design,” The Design Observer Group, posted September 22, 2011,

[15] ARC International Wildlife Crossing Infrastructure Design Competition 2010, Competition Brief, See also

Image Credit

“The TransCanada and the Canadian Pacific Railroad in the Bow River Valley” by Tony Clevenger.

Share on facebook
Share on twitter
Share on linkedin
  • Nina-Marie Lister

    Professor Nina-Marie Lister is tenured Associate Professor of Urban and Regional Planning at Ryerson University in Toronto and Visiting Associate Professor of Landscape Architecture at Harvard University Graduate School of Design.

Scroll to Top