![Forman encourages highway designers to “Think still bigger. Get vehicles off the ground surface, and think how many ecological and human values would be enhanced.” The eco-motorway partially answers this call with an overpass for cars rather than animals. Seventy miles south of Paris, the Loing Viaduct extends nearly a mile, an impressive span that accommodates the meanders of the Loing River and its broad floodplain. Elevation allowed engineers to minimize disturbance to habitats, vegetation and riparian areas during the highway’s construction and operation. [Photo courtesy of Vinci]](https://placesjournal.org/wp-content/uploads/2011/09/tepper-19-road.jpg)
High-speed rail may get the flashy headlines, but most U.S. transportation dollars go to building, widening and maintaining roads. President Obama’s 2012 budget proposal called for substantially increased spending on rail and public transit, but nonetheless allocates 55 percent of transportation funds to the Federal Highway Administration. 1 The United States adds 32,000 lane miles annually to the 4 million miles of public roads already crisscrossing the country. 2 For more than a century, we have allowed expressways, arterials and rural roads to define our landscapes without seriously considering how we might redefine the road. Engineers have rarely attempted to incorporate ecological functions, let alone artistry, into a design practice historically dominated by concerns for speed and efficiency.
In the last decade, the emerging field of road ecology has galvanized scholars and practitioners eager to address this problem. Road ecologists investigate the complex interactions between roads and the natural environment: how roads act as barriers inhibiting the movement of plants, animals, water and soils; how traffic run-off contaminates surface and underground water; and how particulate emissions and noise pollution affect habitats. They also help develop and test solutions to these pervasive problems.
In the last decade, the emerging field of road ecology has galvanized scholars and practitioners eager to address this problem. Road ecologists investigate the complex interactions between roads and the natural environment: how roads act as barriers inhibiting the movement of plants, animals, water and soils; how traffic run-off contaminates surface and underground water; and how particulate emissions and noise pollution affect habitats. They also help develop and test solutions to these pervasive problems.
The practice of road ecology began in Europe in the 1970s and later spread to the U.S. by way of the annual International Conference on Ecology and Transportation. In 2003, the seminal text Road Ecology, written by Richard T.T. Forman and Daniel Sperling along with twelve co-authors, helped to formalize the movement. As Forman explains, the book “pulled the diverse scientific and planning threads of the field together and added distinctive synergisms, resulting in a distinct field which researchers and planners can and do hang their hat on, and push important frontiers.” Major research centers now include the Road Ecology Center at UC Davis, the Center for Transportation and the Environment at North Carolina State University, and the Western Transportation Institute’s Road Ecology Program at Montana State University. The WTI organized last year’s ARC International Wildlife Crossing Infrastructure Design Competition, which brought new momentum and attention to the practice, particularly from architects and landscape architects. In the long term, Forman and many colleagues advocate reducing automobile dependence and removing roads. In the near term, the focus is on innovative design and renovation. As long as we remain politically and financially committed to the highway system, road ecologists say, we must consider not only if, but how we design roads.
Several European countries — notably France, the Netherlands, Switzerland and Germany — mandate an intensive highway design process that integrates environmental factors in the earliest phases of project design and makes extensive use of wildlife crossings and other ecological mitigation infrastructure. The scope of this investment manifests in large-scale systems like the 108 water treatment basins lining France’s new “eco-motorway” and the nine ecoducts (Europe’s equivalent to wildlife overpasses) currently under construction in the Netherlands as part of a national landscape connectivity initiative working towards the creation of a National Ecological Network.
In North America, such large-scale projects are less common; yet the most iconic works of ecological road infrastructure in the world are the six massive wildlife overpasses lining the Trans-Canada Highway in Banff National Park. The overpasses are part of a larger system of ecological infrastructure that Parks Canada began developing in the early 1980s to address concerns about increased traffic and collisions between vehicles and large mammals. The expansion of the crossing system coincides with the phased “twinning” or widening of the Trans-Canada Highway. Ongoing, year-round monitoring by the Banff Wildlife Crossings Project has proven the crossings’ effectiveness at reducing wildlife mortality, and it is also informing the implementation for future phases of the highway expansion. 3
Unfortunately, the monumental overpasses come with an outsized price tag. Parks Canada constructed the first two overpasses at Banff in 1997 for roughly $2.5 million USD each, but the cost for the four additional overpasses last year shot up to between $4.5 and $5 million USD each. The high cost has hindered widespread use. Nonetheless, cost-benefit analyses increasingly include potential financial savings from the $8 billion in property damage that, according to the Federal Highway Administration, results annually from animal-vehicle collisions in the U.S. 4
Banff wildlife ecologist Tony Clevenger sees the high cost of wildlife crossings as a design problem and initiated the ARC Competition as a response. His colleagues at the Western Transportation Institute, together with the Woodcock Foundation, invited interdisciplinary teams to design wildlife overpasses for West Vail Pass, which is along a stretch of I-70 passing through the Rockies 100 miles west of Denver, and to compete for a $40,000 honorarium. The crossings would serve populations of black bear, bighorn sheep, lynx, bobcat, elk, coyote and deer inhabiting the national forests divided by the freeway. Five finalist teams — chosen from a pool of 36 — developed solutions that were not only materially and functionally innovative, but also cost-effective. Finalists included teams led by Balmori Associates, the Olin Studio, Janet Rosenberg & Associates, Zwarts & Jansma Architects; the winner was the team of HNTB and Michael Van Valkenburgh Associates.
The ARC competition generated a store of viable design ideas that add to the substantial body of research the U.S. has already contributed to road ecology; yet Clevenger noted that presently the nation is behind the curve in translating its research into infrastructure, particularly relative to European countries. This photo essay looks at two of the proposals from ARC as well as existing ecological road infrastructure in the U.S. and Europe. The projects, both built and proposed, underscore the promise of road ecology to enhance habitat connectivity and reduce wildlife mortality, and also to ameliorate the broader conflicts between human infrastructure and natural ecosystems.
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Parks Canada initiated the Banff Crossings Project in the mid-1980s to mitigate the effects of a phased Trans-Canada Highway expansion. The twinning of the highway through the National Park has resulted in four lanes divided by a wide green median. The green space preserves a park-like appearance, but the design triples the width of the right-of-way, creating a significant wildlife barrier.
The first phase of wildlife infrastructure at Banff, along a 28-mile pilot corridor, includes 11 underpasses of four distinct types (creek bridges, elliptical metal culverts, prefabricated concrete boxes and an open-span concrete bridge) and miles of eight-foot-high fencing to funnel animals toward the crossings. The bridge shown here creates a 33-foot underpass favored by deer and coyotes. Although wildlife crossings have been built elsewhere, the Banff Project is unique because of the extensive research associated with it, which has generated the world’s largest data set on wildlife use of highway crossings.
The iconic wildlife overpasses along the Trans-Canada Highway in Banff National Park facilitate wildlife movement and protect animals and vehicles from colliding. Six landscaped bridges, each 180 to 200 feet wide, extend habitat across the highway in strategic locations identified by researchers overlaying data about wildlife-vehicle collisions and animal migration patterns. They feature natural elements from the surrounding ecosystems, including immature spruce-pine forest favored by bears and sticks and scree preferred by amphibians and small mammals. Humans (except researchers) are banned from the crossings.
From 1996 to 2010, Banff researchers recorded 11 species of large mammals using 30 wildlife crossings more than 220,000 times. Ongoing monitoring informs successive phases of highway expansion, helping ecologists and engineers identify the most effective types and placement of structures and appropriate dimensions. Early results showed that large carnivores like grizzly bears and wolves were reluctant to use underpasses; although initially they were also wary of the pilot 180-foot-wide overpasses, over a five-year period they changed their migration patterns to accept them. Overpasses constructed in 2010 were expanded to a 200-foot width, based on the observation that animals prefer a more “open” crossing.
The Banff overpasses have been replicated around the world. The structural design — shown in this crossing outside of Oslo, Norway — consists of two single spans with a center support. Canadian engineers developed the corrugated steel structures to meet the same minimum bridge codes as concrete overpasses that accommodate heavy vehicular traffic, even though the crossings only need to support vegetation, substrate, snow and the few animals crossing at any one time. Their bulk contributes to the high cost, which — while not prohibitive in Norway, as the government proceeds with a 100-year infrastructure upgrade — has weighed heavily against their adoption in the United States.
Large overpasses exceed the scope of most American highway budgets, but Banff’s road ecology work resonates in projects like The People’s Way, a 56-mile stretch of US-93 that bisects the Flathead Indian Reservation in Northwest Montana. Perhaps the most ecologically responsive corridor in the U.S. to date, it connects the City of Missoula to Glacier National Park and features 42 fish and wildlife crossings. All but one of these are underpasses, largely imperceptible to drivers. The one single-span overpass occurs along a grizzly migration corridor that made the highway infamous for fatal and costly collisions.
The People’s Way retrofit, completed between 2004 and 2010, originated as a proposal to create a four-lane divided highway, which local opposition blocked for 20 years. The Confederated Salish and Kootenai Tribes, who hold title to the land, successfully redirected plans toward alignment changes that accommodate increased traffic while minimizing encroachment into adjoining wetlands. Landscape architects from Jones and Jones mediated negotiations between tribal, state and federal authorities, and created a design that, as Dale Becker, the Tribes’ Wildlife Program Manager, says, “lays the highway on the land,” protecting wildlife and cultural resources. [Map from Concept Design Plan by Jones and Jones, courtesy of the Confederated Salish and Kootenai Tribes]
Of the $150 million spent on the retrofit, $10.5 million went to wildlife crossings — $1.5 million less than the cost of a single overpass in Banff. The Tribes place high importance on aquatic ecosystems and groundwater quality, so most underpasses coincide with stream crossings, where road ecologists have attended to fish passage, flood plain and wetland protection, and erosion control, as implemented with the geo-textile matting shown here. In the background, a set of stairs known as a “jump out” helps wildlife cross the eight-foot-high fence from the highway side.
Post-project analysis of the People’s Way by the Western Transportation Institute Road Ecology Program uses research methods developed by colleagues in Banff, including monitoring crossings with motion-detecting cameras. The resulting images double as public relations tools, demonstrating the value of the infrastructure and raising support for future projects. Comprehensive road ecology projects are still rare in the U.S., where, as Richard T.T. Forman observes, it takes “states, counties, and municipalities [to] somehow make our hodgepodge work.” Forman contrasts this with Europe’s centralized national and international planning. [Image courtesy of the WTI]
The ARC competition for Vail Pass, organized by WTI, imagines ecological road infrastructure on a grander scale, on par with Banff, but materially and financially more efficient. The Olin Studio’s “Wild (X)ing,” shown here, combines “static and living systems” in habitat modules, which enable vegetation to be easily inserted and removed from the crossing’s structural grid, which is similar to a green roof. Olin envisions glass-reinforced plastic trays that arrive on the site pre-planted with species for one of six distinct habitats: spruce and fir forest, xeric grassland, xeric shrubland, mesic grassland, mesic shrubland and wet meadow. [Image courtesy of the Olin Studio]
Wild (X)ing's scooped shape — a feature shared by several ARC entries — widens in the center and pulls upward at the sides, creating a valley landscape on top that Olin partner David Rubin says “aims for normality” and puts wildlife at ease by blocking sightlines and traffic noise. The arc and perforated ceiling simultaneously maximize light underneath the structure for drivers, mitigating what Rubin perceives as “the tunnel-like qualities” and “heavy, burdened image” of other wildlife crossings. Built-in drainage physically lightens the load, allowing for a more substantial soil profile and mature vegetation. [Image courtesy of the Olin Studio]
While it is unusual for design competitions to emphasize the bottom line, first prize in the ARC went to the lowest bidder, perhaps not coincidentally the only team co-led by engineers and landscape architects. HNTB Engineering’s and Michael Van Valkenburgh and Associates’ technically sophisticated “Hypar-Vault” scales modularly to twice the width of a Banff crossing without a center support and at half the area cost. While many existing wildlife overpasses have an 80-year lifespan, scientists expect migrations to evolve within 30 years as climate patterns shift, which makes this modular design appropriate. Since a module can be lifted with a single crane, construction can proceed without shutting down traffic. [Images courtesy of HNTB and MVVA]
HNTB and MVVA took an aggressive approach to habitat connection, constructing a “Hypar-Nature” that, as MVVA’s Nicholas Pevzner explains, “we could manipulate beyond the extents of the overpass.” In addition to using exclusionary fencing, the crossing actively recruits animals with “habitat bands” attractive to different species, defining migration lanes analogous to highway traffic lanes. Hypar-Nature shuns the romantic ideal of wilderness in North America in favor of a constructed nature more common in Europe. [Image courtesy of HNTB and MVVA]
ARC’s incorporation of high design aesthetics in ecological and transportation infrastructure is familiar in France. French planners built Europe’s first animal crossings in the 1950s to serve as game passages for hunters, well before the term road ecology was coined. These early models — like the wooden bridge pictured — were narrow, sparsely vegetated or bare concrete. Animals were generally in full view and earshot of the road. France’s overpasses have evolved and proliferated; today there are more than 100 around the country.
Due to increasing public opposition to rural road construction, every new and retrofitted highway in France must have a landscape plan that meets national guidelines developed by landscape architect Bernard Lassus on behalf of the Ministry of Highways. Concept drawings for a section of A85 between the cities of Angers and Tours show a patchwork of plantings across the highway rather than along it, so that the highway landscape meshes into the surrounding matrix of vineyards, meadows and forests. [Image courtesy of Bernard Lassus]
This land bridge along A85, shown during its construction phase, is part of a larger system of earthworks that keeps the road below grade and lessens visual and noise pollution. Lassus solicited input from local farmers to inform planting and drainage systems, while grading slopes to their machinery specifications. In Europe, agricultural land is prioritized as highly as wilderness is in North America. “They’ll tunnel a road to protect grazing land,” WTI Road Ecology Program Manager Rob Ament said, citing European precedents as an inspiration for ARC’s design competition. [Photo courtesy of Bernard Lassus]
France’s commitment to “greening” roads is exemplified by the first “eco-motorway,” a 63-mile section of A19, completing the outer bypass of Paris, that opened with great fanfare in June 2009. According to Vinci, the French engineering company that developed the project, “New motorways are not so popular anymore in France.” Public opinion influenced Vinci to create a socially and environmentally appealing road, which includes a laundry list of ecological features: 200,000 new trees, exclusionary wildlife fencing, 116 animal crossings, two 500-foot-wide overpasses and extensive water quality infrastructure. Noise pollution is controlled through five miles of sound barriers and earthen berms.
Vinci equipped the motorway with descriptive signs, such as this one calling attention to one of 108 retention basins that aim to treat 100% of stormwater run-off. Water is funneled off the road via concrete channels and vegetated swales; it then returns to a river at regulated flows or recharges groundwater tables through an infiltration basin. Water quality infrastructure extends to rest stops, where toilets use harvested rainwater, constructed wetlands treat wastewater and solar panels generate electricity and heat water. Forman speculates that in Europe, “greater emphasis on educating the public” makes the cost of ecological infrastructure “more palatable.” tepper-road-19 Forman encourages highway designers to “Think still bigger. Get vehicles off the ground surface, and think how many ecological and human values would be enhanced.” The eco-motorway partially answers this call with an overpass for cars rather than animals. Seventy miles south of Paris, the Loing Viaduct extends nearly a mile, an impressive span that accommodates the meanders of the Loing River and its broad floodplain. Elevation allowed engineers to minimize disturbance to habitats, vegetation and riparian areas during the highway’s construction and operation. [Photo courtesy of Vinci] tepper-road-20 Dutch engineers do not hesitate to take infrastructure off the ground. Their innovations in water management have informed roadways and ecological infrastructure. The “aqueduct” shown here allows A4 to cross a circular canal south of Amsterdam. The road moves under the water, exemplifying an aggressive strategy of combining or stacking land uses. This prevents the highway from disrupting existing habitat or agricultural lands. [Image from A4 Deltaroute Plan (pdf), courtesy of the Rijkswaterstaat] tepper-road-21 Efforts to green the Dutch road network are part of a vision to expand and connect existing nature reserves into a National Ecological Network by 2016. In a country as dense as the Netherlands, creating connectivity requires creativity. Adapting the road system to the Ecological Network is crucial to its success. This map from the Rijkswaterstaat, the Dutch Ministry of Road and Waterway, shows hot spots where roads interfere with the goal of ecological connectivity. National connectivity plans, especially in the Netherlands, France and Germany, have spurred continent-wide initiatives like the emerging Infra Eco Network. [Map courtesy of the Rijkswaterstaat] tepper-road-22 The Netherlands began building animal crossings in the mid-20th century and has since built more than 600 “ecoducts,” used primarily by deer, small mammals and amphibians. This picture shows the country’s first ecoduct, in the Hoge Veluwe National Park. A recent contract will install nine new ecoducts in the next two years. However, the trend of “co-use” most evident in the world’s longest ecoduct, the Natuurbrug Zanderij Crailo — which extends 800 meters across a rail line, two roads, a river, a business park and sports complex — has yet to demonstrate its ecological efficacy. tepper-road-23 Each Dutch National Highway has a comprehensive landscape plan that addresses its place within the road, water and landscape systems and includes measures for dealing with air and noise pollution, water quality and habitat. At the Rijkswaterstaat, engineers, landscape architects, policymakers and ecologists share office space. Their collaboration generates elegant combinations of systems, heavily engineered but with nature’s best interests in mind. [Image from A4 Deltaroute Plan, Rijkswaterstaat] tepper-road-24 The Dutch National Eco-Compensation Program requires habitat replacement at a 1:1 area ratio. This highway junction along A12 speaks to the program’s slogan, “New Road; New Nature.” Rijkswaterstaat landscape architect Jan Willem de Jager designed the central highway loop to encompass a water retention basin and wet meadow habitat. Like most Dutch road projects, it also includes a separated bike path. Jager notes that Dutch highways often incorporate earth berms for support, drainage and noise screening because they are easy to maintain, inexpensive and resistant to structural failure. [Site plan and photograph courtesy of Jan Willem de Jager, Rijkswaterstaat] tepper-road-25 Innovations like noise-reducing, porous asphalt, smog-absorbing coating for sound barriers, and roll-out paving emerge regularly from the Rijkwaterstaat’s “Roads to the Future” program, which supports research into new materials and techniques for transportation infrastructure. The Dutch highway system will inevitably be retrofitted, not expanded — there is simply no room for more roads. However, the same techniques can be applied toward ecologically responsive road design in countries that are building new roads, where, as Ament notes, engineers “have the opportunity to do smart design from the outset.” Collaboration between scientists, landscape
Forman encourages highway designers to “Think still bigger. Get vehicles off the ground surface, and think how many ecological and human values would be enhanced.” The eco-motorway partially answers this call with an overpass for cars rather than animals. Seventy miles south of Paris, the Loing Viaduct extends nearly a mile, an impressive span that accommodates the meanders of the Loing River and its broad floodplain. Elevation allowed engineers to minimize disturbance to habitats, vegetation and riparian areas during the highway’s construction and operation. [Photo courtesy of Vinci]
Dutch engineers do not hesitate to take infrastructure off the ground. Their innovations in water management have informed roadways and ecological infrastructure. The “aqueduct” shown here allows A4 to cross a circular canal south of Amsterdam. The road moves under the water, exemplifying an aggressive strategy of combining or stacking land uses. This prevents the highway from disrupting existing habitat or agricultural lands. [Image from A4 Deltaroute Plan (pdf), courtesy of the Rijkswaterstaat]
Efforts to green the Dutch road network are part of a vision to expand and connect existing nature reserves into a National Ecological Network by 2016. In a country as dense as the Netherlands, creating connectivity requires creativity. Adapting the road system to the Ecological Network is crucial to its success. This map from the Rijkswaterstaat, the Dutch Ministry of Road and Waterway, shows hot spots where roads interfere with the goal of ecological connectivity. National connectivity plans, especially in the Netherlands, France and Germany, have spurred continent-wide initiatives like the emerging Infra Eco Network. [Map courtesy of the Rijkswaterstaat]
The Netherlands began building animal crossings in the mid-20th century and has since built more than 600 “ecoducts,” used primarily by deer, small mammals and amphibians. This picture shows the country’s first ecoduct, in the Hoge Veluwe National Park. A recent contract will install nine new ecoducts in the next two years. However, the trend of “co-use” most evident in the world’s longest ecoduct, the Natuurbrug Zanderij Crailo — which extends 800 meters across a rail line, two roads, a river, a business park and sports complex — has yet to demonstrate its ecological efficacy. tepper-road-23 Each Dutch National Highway has a comprehensive landscape plan that addresses its place within the road, water and landscape systems and includes measures for dealing with air and noise pollution, water quality and habitat. At the Rijkswaterstaat, engineers, landscape architects, policymakers and ecologists share office space. Their collaboration generates elegant combinations of systems, heavily engineered but with nature’s best interests in mind. [Image from A4 Deltaroute Plan, Rijkswaterstaat] tepper-road-24 The Dutch National Eco-Compensation Program requires habitat replacement at a 1:1 area ratio. This highway junction along A12 speaks to the program’s slogan, “New Road; New Nature.” Rijkswaterstaat landscape architect Jan Willem de Jager designed the central highway loop to encompass a water retention basin and wet meadow habitat. Like most Dutch road projects, it also includes a separated bike path. Jager notes that Dutch highways often incorporate earth berms for support, drainage and noise screening because they are easy to maintain, inexpensive and resistant to structural failure. [Site plan and photograph courtesy of Jan Willem de Jager, Rijkswaterstaat] tepper-road-25 Innovations like noise-reducing, porous asphalt, smog-absorbing coating for sound barriers, and roll-out paving emerge regularly from the Rijkwaterstaat’s “Roads to the Future” program, which supports research into new materials and techniques for transportation infrastructure. The Dutch highway system will inevitably be retrofitted, not expanded — there is simply no room for more roads. However, the same techniques can be applied toward ecologically responsive road design in countries that are
Each Dutch National Highway has a comprehensive landscape plan that addresses its place within the road, water and landscape systems and includes measures for dealing with air and noise pollution, water quality and habitat. At the Rijkswaterstaat, engineers, landscape architects, policymakers and ecologists share office space. Their collaboration generates elegant combinations of systems, heavily engineered but with nature’s best interests in mind. [Image from A4 Deltaroute Plan, Rijkswaterstaat]
The Dutch National Eco-Compensation Program requires habitat replacement at a 1:1 area ratio. This highway junction along A12 speaks to the program’s slogan, “New Road; New Nature.” Rijkswaterstaat landscape architect Jan Willem de Jager designed the central highway loop to encompass a water retention basin and wet meadow habitat. Like most Dutch road projects, it also includes a separated bike path. Jager notes that Dutch highways often incorporate earth berms for support, drainage and noise screening because they are easy to maintain, inexpensive and resistant to structural failure. [Site plan and photograph courtesy of Jan Willem de Jager, Rijkswaterstaat]
Innovations like noise-reducing, porous asphalt, smog-absorbing coating for sound barriers, and roll-out paving emerge regularly from the Rijkwaterstaat’s “Roads to the Future” program, which supports research into new materials and techniques for transportation infrastructure. The Dutch highway system will inevitably be retrofitted, not expanded — there is simply no room for more roads. However, the same techniques can be applied toward ecologically responsive road design in countries that are building new roads, where, as Ament notes, engineers “have the opportunity to do smart design from the outset.” Collaboration between scientists, landscape architects and engineers may be the key to protecting land threatened by the 3100 miles of new roads built annually in China, such as the Guizhou highway shown here. [Photo by Sweart via Flickr]
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