Road crossings for Wildlife history and current projects
Onsite Audio File:How Wildlife Bridges Reconnect the Wild.m4a
Wildlife Crossings and the Global Rise of Road Ecology
Wildlife crossings are specially designed structures that help animals move safely across roads, railways, and other transportation corridors. They include vegetated overpasses, tunnels, culverts, canopy bridges, amphibian passages, escape poles, fencing systems, and animal-detection technology. Together, these measures form an important part of road ecology, the study of how transportation networks affect wildlife, habitats, water, vegetation, and ecological processes.
Roads can divide habitats, interrupt migration routes, isolate animal populations, and cause large numbers of wildlife-vehicle collisions. Crossing structures seek to reduce these impacts by restoring movement between fragmented areas while also improving safety for motorists.
Why Wildlife Crossings Are Needed
Transportation infrastructure can create major ecological barriers. Animals attempting to cross busy roads may be injured or killed, while animals that avoid roads may lose access to food, mates, seasonal ranges, breeding areas, and climate refuges.
Habitat fragmentation can also isolate populations and reduce genetic diversity. These effects are especially serious for wide-ranging species such as mountain lions, elephants, bears, elk, deer, pronghorn, and wolves. Smaller animals, including salamanders, frogs, turtles, snakes, crabs, monkeys, koalas, and sloths, face different but equally significant risks.
Wildlife crossings address these problems by providing routes designed around the movement patterns, physical abilities, and behavioral needs of particular species.
Major Types of Wildlife Crossings
Wildlife overpasses, sometimes called green bridges or ecoducts, are broad bridges covered with soil, native plants, rocks, and other natural features. They are often used by large mammals and can reconnect entire habitat corridors across major highways.
Underpasses and culverts allow animals to move beneath roads. Their effectiveness depends on dimensions, lighting, moisture, vegetation, surrounding terrain, and the species expected to use them. Large underpasses may accommodate elephants, deer, elk, mountain lions, and giraffes, while smaller tunnels may serve amphibians, reptiles, and other small animals.
Canopy bridges connect trees above roads and are designed for arboreal animals such as monkeys, sloths, possums, and other climbing species. Rope bridges and suspended mesh structures are commonly used in tropical forests and urban areas.
Species-specific measures include koala escape poles, crab bridges, salamander tunnels, fish passages, and fencing designed for animals of different sizes. These projects demonstrate that no single crossing design works equally well for every species.
The Importance of Fencing and Placement
Crossing structures are generally most effective when paired with fencing. Fencing guides animals toward safe passages and prevents them from entering dangerous sections of roadway. Poorly designed fencing can trap animals or create new barriers, so escape routes, jump-outs, gates, and maintenance are important.
Location is equally important. Researchers use roadkill records, GPS tracking, camera traps, migration data, habitat mapping, genetic studies, and computer modeling to identify collision hotspots and important movement corridors.
A crossing built in the wrong place may receive little use, even when its physical design is sound. Strategic placement based on scientific evidence can improve ecological effectiveness and make better use of limited public funding.
Species Respond Differently to Crossing Designs
Different animals respond to crossing structures in different ways. Some species readily use enclosed tunnels, while others prefer open structures with natural light and vegetation. Predators and prey may avoid passages used heavily by people, livestock, or competing species.
Research in Banff National Park and other locations has shown that crossing width, height, length, vegetation, noise, human activity, and proximity to suitable habitat all influence animal behavior.
Monitoring is therefore essential. Cameras, tracks, genetic sampling, sensors, and field surveys help determine whether animals are using a crossing and whether the project is restoring movement at the population level.
Wildlife Crossings in the United States
The United States has expanded federal and state support for wildlife-crossing infrastructure. The federal Wildlife Crossings Pilot Program funds construction, planning, mapping, monitoring, fencing, engineering, and related activities intended to reduce wildlife-vehicle collisions and reconnect habitats.
Federal grant rounds have supported projects in numerous states. State governments have also created dedicated programs, appropriations, partnerships, and transportation-planning requirements.
Colorado has developed major overpasses and underpasses for elk, mule deer, pronghorn, and other species. The Greenland Wildlife Overpass across Interstate 25 is among the largest wildlife bridges in North America.
Wyoming’s Trapper’s Point system protects an ancient pronghorn migration route and is frequently cited as an example of a wildlife-crossing investment producing long-term economic benefits through collision reduction.
Utah has constructed crossings along major transportation corridors and approved substantial state funding for additional projects. The Interstate 80 overpass in Parleys Canyon serves deer, elk, moose, bears, and other wildlife.
California projects include the Wallis Annenberg Wildlife Crossing over Highway 101, the Laurel Curve underpass beneath Highway 17, and a State Route 97 overcrossing used by mule deer even before construction was fully complete.
Other notable programs exist in Arizona, Nevada, Oregon, Washington, Montana, Florida, New Jersey, New York, Massachusetts, and Vermont.
California Wildlife Connectivity Projects
California contains many roads that divide important habitats. The Wallis Annenberg Wildlife Crossing is intended to reconnect the Santa Monica Mountains with habitat north of Highway 101. The project is designed for mountain lions as well as smaller mammals, reptiles, insects, and plants.
The Laurel Curve wildlife underpass beneath Highway 17 in the Santa Cruz Mountains provides a safer passage for mountain lions, deer, bobcats, and other animals. Monitoring has confirmed its use, although conservationists argue that additional crossings are needed throughout the region.
Coyote Valley is another important connectivity area linking the Santa Cruz Mountains and the Diablo Range. Conservation planning there seeks to preserve wildlife movement across roads, developed land, and other barriers.
California also supports statewide connectivity mapping, wildlife-crossing guidance, and roadkill reporting through agencies, universities, land trusts, and conservation organizations.
International Wildlife-Crossing Projects
Canada’s Banff National Park contains one of the world’s best-known and longest-running wildlife-crossing systems. Fencing, overpasses, and underpasses along the Trans-Canada Highway have reduced collisions and allowed animals to move between habitats.
The Netherlands has developed numerous ecoducts across highways and railways. Natuurbrug Zanderij Crailoo is a large land bridge spanning transportation infrastructure and developed areas near Hilversum.
Australia uses crossings for koalas, kangaroos, possums, reptiles, amphibians, and other animals. Christmas Island employs bridges, tunnels, barriers, and road closures to help millions of red crabs complete their annual migration to the ocean.
Costa Rica has installed canopy bridges for monkeys, sloths, and other tree-dwelling animals. Scientists there also use ecological data to identify priority locations for road mitigation.
Kenya has constructed railway and highway underpasses in the Tsavo ecosystem. Research indicates that elephants and other animals use these structures differently depending on design and surrounding habitat.
India has developed wildlife underpasses along transportation corridors used by tigers, elephants, and other species. Singapore’s Eco-Link at BKE reconnects forest reserves separated by a major urban expressway.
Wildlife-crossing programs and research also exist in Germany, France, China, Botswana, Brazil, and throughout Europe.
Economic and Public-Safety Benefits
Wildlife-vehicle collisions can cause injuries, deaths, vehicle damage, emergency-response costs, insurance claims, and economic losses. Large-animal crashes involving deer, elk, moose, cattle, or bears can be especially dangerous.
Well-placed crossings and fencing can substantially reduce collisions. When avoided crash costs are measured over many years, some projects can eventually pay for themselves.
Crossings can also protect tourism, hunting, wildlife-watching, ecosystem services, and rural transportation networks. These combined benefits have encouraged governments to treat wildlife infrastructure as both a conservation measure and a public-safety investment.
Federal and State Funding
Funding sources include federal transportation grants, state appropriations, fuel taxes, vehicle fees, bonds, mitigation funds, conservation programs, tribal partnerships, local governments, and private donations.
Federal programs have awarded hundreds of millions of dollars for wildlife-crossing construction, planning, mapping, and monitoring. State initiatives in Colorado, Utah, Oregon, Virginia, Nevada, Wyoming, and other locations demonstrate growing political support for dedicated funding.
Long-term funding is important because successful projects require planning, land acquisition, engineering, environmental review, construction, monitoring, maintenance, and repair.
Research and the Development of Road Ecology
Road ecology developed from research showing that roads influence wildlife mortality, habitat quality, animal abundance, water flow, vegetation, invasive species, pollution, noise, and landscape connectivity.
Foundational studies examined the effects of roads on animal populations and the factors that influence crossing use. Later research has focused on fencing effectiveness, genetic connectivity, optimal crossing placement, climate adaptation, and population-level outcomes.
Researchers increasingly use computer models to compare crossing locations and design networks that reconnect several habitats at the lowest practical cost. These tools can help transportation planners prioritize investments where ecological and safety benefits are greatest.
Community Science and Local Participation
Community volunteers play an important role in identifying migration routes and roadkill hotspots. Salamander-crossing brigades in the northeastern United States help amphibians cross roads during spring migrations while collecting useful scientific data.
Public roadkill-reporting systems allow residents to document collision locations. These observations can reveal patterns that official crash reports may miss and can help agencies identify candidates for fencing, tunnels, signs, speed reductions, or larger crossing structures.
Partnerships among transportation departments, wildlife agencies, tribes, universities, land trusts, nonprofit organizations, and local communities are often essential to project success.
Design Challenges and Limitations
Wildlife crossings are not a complete solution to habitat loss. A bridge or tunnel cannot protect a migration route if surrounding habitat is later developed or if animals cannot reach the structure safely.
Projects may also face high construction costs, land-use conflicts, political opposition, maintenance problems, and uncertainty about long-term ecological outcomes.
Some crossings restore individual animal movement without yet providing clear evidence of population recovery. Others may work well for one species but poorly for another. Monitoring and adaptive management are necessary to address these limitations.
The Future of Wildlife-Friendly Transportation
Future transportation systems are likely to incorporate wildlife connectivity earlier in planning and design. Rather than adding mitigation after roads are built, agencies can identify important corridors before construction begins.
Climate change increases the importance of connected landscapes because animals may need to shift their ranges in response to drought, wildfire, changing temperatures, and altered vegetation.
New technologies, including remote cameras, acoustic sensors, GPS collars, automated animal-detection systems, artificial intelligence, and improved ecological modeling, may help planners design more effective projects.
Wildlife crossings also provide an opportunity to combine engineering, landscape architecture, ecology, public safety, and community planning. Their growth reflects a broader recognition that transportation infrastructure should move people and goods without unnecessarily severing the ecosystems through which it passes.
Conclusion
Wildlife crossings have developed from isolated experiments into a global conservation and transportation strategy. Overpasses, underpasses, canopy bridges, fencing, tunnels, escape structures, and detection systems can reduce animal deaths, prevent costly crashes, and reconnect fragmented habitats.
The most effective projects are based on scientific research, carefully located, designed for local species, paired with appropriate fencing, and monitored over time. Continued public investment, international cooperation, and community participation will be necessary to expand these systems.
As roads continue to shape landscapes around the world, wildlife-friendly transportation offers a practical way to improve human safety while preserving the movement and survival of animals.
News and Recent Developments
Successful California Wildlife Tunnel Is Just the Start for Struggling Pumas
| Julie Brown | SFGATE | July 2026
The Laurel Curve wildlife underpass beneath Highway 17 is being used by mountain lions, deer, bobcats and other animals, but conservationists say additional crossings are still needed.
New Koala Poles Installed Along Gold Coast Wildlife Hotspot
| Staff | Gold Coast Bulletin | July 2026
Five specially designed escape poles are being installed along a dangerous Australian road to help koalas leave the roadway and return safely to surrounding habitat.
Mule Deer Make History on California’s First State-Built Wildlife Overcrossing
Mule deer began using the new State Route 97 wildlife overcrossing in Siskiyou County before construction was fully completed.
How Wildlife Crossings Are Reconnecting Habitats Around the World
| Eco-Business | Eco-Business | June 29, 2026
Wildlife overpasses, underpasses, tunnels and fencing are increasingly being used worldwide to reduce animal deaths and reconnect habitats divided by roads.
The Case for More Wildlife Crossings
| Staff | Earth.Org | May 14, 2026
Wildlife crossings are presented as an increasingly important response to habitat fragmentation, road mortality and declining ecological connectivity.
Can Green Bridges Help Animals Cross Britain’s Motorways?
| Patrick Greenfield | The Guardian | May 12, 2026
Britain’s Cockrow green bridge reconnects protected heathland across the A3 and provides safe passage for deer, reptiles, insects and other wildlife.
California’s Wildlife Bridge Became a Political Target
| Gabrielle Canon | The Guardian | April 25, 2026
The Wallis Annenberg Wildlife Crossing has faced political criticism even as construction continues toward its revised 2026 completion target.
Largest Wildlife Overpass in North America Saving People and Animals
| Staff | New York Post | April 4, 2026
Colorado’s Greenland Wildlife Overpass reconnects thousands of acres of habitat across Interstate 25 and is expected to sharply reduce wildlife collisions.
A Bridge for Giants: Elephants Use Bengaluru’s First Wildlife Overpass
| Staff | Times of India | March 2026
Camera traps documented elephants using a planted overpass connecting Bannerghatta National Park with nearby forest habitat.
How Wildlife Crossings Revolutionized Conservation
| Yellowstone to Yukon Conservation Initiative | Y2Y | October 19, 2025
The article describes how Banff’s crossing system reduced collisions and became an international model for road ecology.
Wildlife Crossings Seek to Reconnect the Animal West
| Felicity Barringer | Stanford University | September 29, 2022
Western states are increasingly constructing overpasses and underpasses to reconnect migration routes and reduce wildlife collisions.
Animal Crossings Helping Wildlife Navigate Busy Roads
| Patrick Greenfield | The Guardian | December 29, 2021
International examples include tiger corridors, crab bridges, possum tunnels and other structures designed for animals of different sizes.
How Wildlife Bridges Make Animals and People Safer
| Starre Vartan | National Geographic | April 16, 2019
Wildlife bridges and tunnels have reduced animal-vehicle collisions in locations ranging from Canada to Australia.
Funding, Policy and Government Programs
How Four States Are Funding Wildlife Crossings for Better Safety
| Noel Fletcher | Forbes | May 31, 2026
Colorado, Oregon, Utah and Virginia have pursued new state funding policies intended to expand wildlife-crossing infrastructure.
The State of Colorado’s Wildlife Crossings
| Environment Colorado Research and Policy Center | Environment America | October 31, 2025
This overview examines completed, planned and proposed wildlife-crossing projects throughout Colorado.
Five Reasons for Colorado to Build More Wildlife Crossings
| Pew Charitable Trusts | Pew | August 13, 2025
The article outlines the safety, conservation and long-term economic benefits of constructing more wildlife crossings in Colorado.
Wildlife-Crossing Pilot Program Grant Selections
| Federal Highway Administration | FHWA | December 2024
The project list describes individual federal grants for wildlife overpasses, underpasses, fencing, planning and monitoring.
Wildlands Network Celebrates New Federal Crossing Grants
| Wildlands Network | Wildlands Network | December 20, 2024
The announcement highlights projects such as the Mammoth Lakes crossing system intended to protect mule-deer migration routes.
FHWA Announces 2024–2025 Wildlife-Crossing Grant Selections
| Federal Highway Administration | FHWA | December 20, 2024
The selection page identifies federally supported construction, planning, mapping and design projects in 16 states.
Federal Government Awards $125 Million for Wildlife Crossings
| U.S. Department of Transportation | USDOT | December 20, 2024
Federal grants were awarded to 16 projects designed to reduce wildlife-vehicle collisions and improve habitat connectivity.
Wildlife Crossings Save Lives, Money and Improve the Environment
| Pew Charitable Trusts | Pew | November 5, 2024
Wildlife crossings can simultaneously reduce vehicle crashes, lower public costs and reconnect wildlife populations.
Nevada Should Boost Funding for Wildlife Crossings
| Pew Charitable Trusts | Pew | June 25, 2024
Nevada has built dozens of animal crossings, but advocates argue that a permanent funding source is needed to expand the system.
Utah Leads the Way on Wildlife Crossings
| Jennifer S. Holland | Pew Trust Magazine | February 2, 2024
Utah’s wildlife-crossing investments build on decades of work protecting migrating deer, elk, pronghorn and other animals.
Federal Investments in Habitat Restoration and Wildlife Crossings
| U.S. Department of Transportation | USDOT | December 6, 2023
The federal overview explains how transportation funding can support habitat restoration, pollinator projects and wildlife crossings.
Federal Government Awards First $110 Million in Crossing Grants
| U.S. Department of Transportation | USDOT | December 5, 2023
The first major round of federal Wildlife Crossings Pilot Program grants supported projects intended to prevent crashes and reconnect habitats.
States Need Dedicated Wildlife-Crossing Funding
| Pew Charitable Trusts | Pew | May 2, 2023
Dedicated state funding can help transportation agencies plan crossing projects before collision hotspots become more dangerous and expensive.
Funding for Wildlife-Crossing Infrastructure
| ECONorthwest | Pew Charitable Trusts | April 2023
This detailed report assesses state-level revenue sources that could support wildlife overpasses, underpasses and related fencing.
States Can Help Pay for New Wildlife Crossings
| Pew Charitable Trusts | Pew | April 27, 2023
The report evaluates fuel taxes, vehicle fees, bonds, appropriations and other mechanisms for funding crossing infrastructure.
United States Launches First Wildlife Crossings Pilot Program
| U.S. Department of Transportation | USDOT | April 4, 2023
The federal program marked the first dedicated national funding initiative for reducing wildlife-vehicle crashes through crossing infrastructure.
Wildlife Crossings Benefit Animals, People and Climate
| Pew Charitable Trusts | Pew | February 14, 2023
Experts recommend incorporating wildlife connectivity into transportation planning while considering climate change and Indigenous knowledge.
Out West, Wildlife Crossings Bring a Return on Investment
| Pew Charitable Trusts | Pew | February 25, 2020
Wyoming’s Trapper’s Point crossing system greatly reduced collisions and demonstrated that crossing investments can eventually pay for themselves.
Wyoming Wildlife-Crossing Initiative
| Wyoming Wildlife and Roadways Initiative | State and nonprofit partnership | Current
The initiative raises funds and public support for crossing projects at Wyoming’s highest-priority wildlife-collision locations.
Wildlife Crossings Reduce Crashes and Restore Connectivity
| Pew Charitable Trusts | Pew | Current
Pew’s wildlife-crossing initiative promotes state and federal policies that support safer roads and connected habitats.
European Green Infrastructure
| European Commission | European Union | Current
European green-infrastructure policy supports ecological corridors and measures that reduce fragmentation caused by transportation networks.
Colorado Wildlife and Transportation Alliance
| Colorado Department of Transportation | CDOT | Current
State agencies and conservation organizations coordinate research, planning and funding for wildlife-road mitigation in Colorado.
North American Projects and Initiatives
Highway 17 Wildlife Connectivity
| University of California, Santa Cruz | UC Santa Cruz | 2023
Researchers and conservationists monitor how mountain lions and other wildlife respond to the new Highway 17 underpass.
Wallis Annenberg Wildlife Crossing Construction Update
| Tara Lynn Wagner | Spectrum News | November 23, 2023
The crossing over Highway 101 is designed to reconnect habitat used by mountain lions and numerous smaller species in the Santa Monica Mountains.
Utah Approves $20 Million for Wildlife Crossings
| Pew Charitable Trusts | Pew | March 24, 2023
Utah approved one of the nation’s largest state appropriations specifically dedicated to wildlife-crossing infrastructure.
Yoho National Park Highway Twinning and Wildlife Crossings
| Parks Canada | Government of Canada | Current project
Trans-Canada Highway improvements through Yoho National Park include wildlife crossings, fencing and habitat-protection measures.
Washington Habitat Connectivity
Scientists map wildlife corridors and climate linkages that can inform road-crossing and land-conservation decisions.
Wallis Annenberg Wildlife Crossing Project
| California Department of Transportation | Caltrans | Current project
The vegetated bridge over Highway 101 is intended to reconnect the Santa Monica Mountains with habitat to the north.
U.S. Highway 93 Wildlife Crossings in Montana
| ARC Solutions | ARC Solutions | Current
Highway 93 includes extensive fencing and dozens of crossings created with tribal participation on the Flathead Indian Reservation.
Trapper’s Point Wildlife Crossing
| Wyoming Wildlife Federation | Wyoming Wildlife Federation | Current
Two overpasses and several underpasses protect the ancient Path of the Pronghorn migration corridor near Pinedale, Wyoming.
State Route 260 Wildlife Crossings
| Arizona Department of Transportation | ADOT | Project history
Crossing structures and fencing along State Route 260 have significantly reduced elk and deer collisions.
Robert L.B. Tobin Land Bridge
| Phil Hardberger Park Conservancy | Phil Hardberger Park | Current
The San Antonio land bridge reconnects two sections of urban parkland divided by Wurzbach Parkway.
Peter Lougheed Wildlife Overpass
| DIALOG | DIALOG | Current project
The Alberta crossing was designed to provide a safe, ecologically appropriate route for wildlife over a busy highway.
Paynes Prairie Wildlife Crossing
| Florida Museum of Natural History | University of Florida | Project history
A barrier wall and culvert system along U.S. Highway 441 protects snakes, turtles, frogs and other wetland wildlife.
Oregon Wildlife Corridors
| Oregon Department of Fish and Wildlife | ODFW | Current
Oregon’s movement strategy identifies priority habitats, migration routes and locations where roads interfere with animal movement.
Oracle Road Wildlife Crossings
| Federal Highway Administration | FHWA | Project history
Wildlife bridges and underpasses north of Tucson were designed to reconnect Sonoran Desert habitat divided by State Route 77.
Nevada Wildlife Crossings
| Nevada Department of Transportation | NDOT | Current
Nevada’s crossing network includes large overpasses and underpasses serving mule deer, pronghorn and other desert wildlife.
Montana Wildlife and Transportation Partnership
| Montana Department of Transportation | MDT | Current
Montana uses fencing, underpasses, bridges and other accommodations to reduce highway impacts on wildlife.
Laurel Curve Wildlife Crossing
| Land Trust of Santa Cruz County | Land Trust of Santa Cruz County | Current
The Highway 17 tunnel and fencing system provides mountain lions and other animals with a safer route through the Santa Cruz Mountains.
Kootenay National Park Wildlife Crossings
| Parks Canada | Government of Canada | Current
Wildlife fencing and crossing structures along Highway 93 South help protect animals moving through the Canadian Rockies.
Keechelus Wildlife Overcrossing
| Conservation Northwest | Conservation Northwest | Current
The Keechelus overcrossing is part of a larger effort to reconnect wildlife habitat across Interstate 90 in Washington.
Interstate 90 Snoqualmie Pass Wildlife Crossings
| Washington State Department of Transportation | WSDOT | Current project
The Interstate 90 reconstruction includes bridges, culverts and a vegetated overpass reconnecting Cascade Mountain habitat.
I-25 Greenland Wildlife Overpass
| Colorado Department of Transportation | CDOT | Current project
The large Colorado overpass was designed primarily for elk, mule deer and pronghorn moving through the Interstate 25 corridor.
Coyote Valley Wildlife Crossings
| Santa Clara Valley Open Space Authority | Open Space Authority | Current project
Conservation planning in Coyote Valley includes efforts to maintain wildlife movement across roads connecting the Santa Cruz Mountains and Diablo Range.
Colorado Wildlife-Crossing Project Map
| Colorado Department of Transportation | CDOT | Current
Colorado documents crossing structures, collision-reduction projects and wildlife-sensitive transportation planning throughout the state.
California Wildlife Crossing Guidance
| California Department of Transportation | Caltrans | Current
Caltrans provides information on planning, designing and monitoring structures intended to improve wildlife movement.
California Wildlife Connectivity
| California Department of Fish and Wildlife | CDFW | Current
California’s connectivity program identifies important movement corridors and supports projects that reconnect habitats across roads and development.
Banff National Park Wildlife Crossings
| Parks Canada | Government of Canada | Current
Banff’s system of fencing, overpasses and underpasses is one of the world’s longest-running wildlife-road mitigation programs.
Arizona Wildlife Linkages
| Arizona Department of Transportation | ADOT | Current
Arizona identifies important wildlife linkages and incorporates crossing structures into transportation projects.
International Crossings and Programs
Canopy Bridges for Primates
| Staff | Mongabay | March 2021
Aerial bridges are increasingly used to reconnect forest canopies for monkeys and other arboreal animals.
Toohey Forest Koala Underpass
| Brisbane City Council | Brisbane City Council | Current project
Brisbane is developing an under-road passage with guide fencing, escape points and refuge poles for koalas and other forest animals.
Slaty Creek Wildlife Underpass
The large underpass beneath the Calder Freeway has been monitored for use by mammals, reptiles, amphibians, birds and other fauna.
Singapore Eco-Link at BKE
| National Parks Board | Government of Singapore | Current
The forested bridge over the Bukit Timah Expressway reconnects two nature reserves separated by a major urban highway.
NH-44 Wildlife Underpasses in India
| Wildlife Trust of India | Wildlife Trust of India | Current
Underpasses along National Highway 44 allow tigers and other animals to move between protected habitats in central India.
Natuurbrug Zanderij Crailoo
| Goois Natuurreservaat | Goois Nature Reserve | Current
This extensive Dutch ecoduct spans a highway, railway and other developed land while connecting natural habitat near Hilversum.
Kenya’s Tsavo Wildlife Underpasses
| Save the Elephants | Save the Elephants | Current
Research and monitoring examine how elephants respond to railway and highway crossing structures in the Tsavo ecosystem.
India’s Wildlife Crossings and Linear Infrastructure
| Wildlife Institute of India | Government of India | Current
Indian researchers develop guidance for reducing the effects of highways, railways and power lines on elephants, tigers and other wildlife.
Germany’s Wildlife Bridges
| German Federal Agency for Nature Conservation | BfN | Current
Germany’s habitat-connectivity programs include green bridges and other measures for reconnecting landscapes divided by highways.
France’s Green Bridges and Wildlife Passages
| Cerema | French Government | Current
French transportation authorities use ecological passages to reduce habitat fragmentation and improve movement across infrastructure.
Ecoducts of the Netherlands
| Wageningen University and Research | WUR | Current
Dutch researchers study how green bridges, tunnels and fencing reconnect habitats across one of Europe’s densest road networks.
Costa Rica Canopy Bridges
| Wild Sun Rescue Center | Wild Sun Rescue | Current
Rope and canopy bridges help monkeys, sloths and other tree-dwelling species cross roads without descending into traffic.
Christmas Island Crab Crossings
| Parks Australia | Australian Government | Current
Bridges, tunnels and temporary road closures help millions of red crabs reach the ocean during their annual migration.
Brisbane Compton Road Fauna Crossing
| Brisbane City Council | Brisbane City Council | Current
The Australian crossing system combines a vegetated bridge, underpasses, canopy ropes and fencing for koalas and other urban wildlife.
Botswana Wildlife-Friendly Roads
| Kalahari Conservation Society | KCS | Current
Conservation planning in Botswana examines how roads and fences influence elephant and other wildlife movement.
Species-Specific and Community Crossing Efforts
Vermont Amphibian Road Crossings
| Vermont Center for Ecostudies | VCE | Current
Volunteers document and assist salamanders and frogs crossing roads during spring migrations to breeding pools.
Salamander Crossing Brigades
| Harris Center for Conservation Education | Harris Center | Current
Community volunteers help amphibians cross roads while collecting data that can support permanent tunnels and barriers.
New York Amphibian Migrations and Road Crossings
| New York Department of Environmental Conservation | NYDEC | Current
Volunteers record frogs and salamanders crossing roads in the Hudson Valley and help them reach breeding wetlands.
New Jersey Amphibian-Crossing Project
| New Jersey Department of Environmental Protection | NJDEP | Current
New Jersey monitors amphibian migration sites and works with communities to reduce road deaths.
Henry Street Salamander Tunnels
| Town of Amherst | Amherst, Massachusetts | Project history
Small tunnels beneath Henry Street became a pioneering American effort to protect spotted salamanders during seasonal migrations.
Florida Panther Highway Crossings
| Florida Fish and Wildlife Conservation Commission | FWC | Current
Underpasses, fencing and reduced-speed zones are used to protect endangered Florida panthers from vehicle collisions.
Research, Design and Effectiveness Studies
Placing Green Bridges Optimally With Close-Range Habitats
| Christian Wallisch, Till Fluschnik and Leon Kellerhals | arXiv | October 24, 2025
Researchers examine computational methods for choosing cost-effective green-bridge locations within fragmented habitat networks.
How Well Do Wildlife-Crossing Structures Help Animals?
| Kylie Soanes | Transport Ecology | January 22, 2025
Research findings indicate that crossings generally restore animal movement, although effectiveness depends on design, fencing, location and species behavior.
Identifying Wildlife-Road Mitigation Sites in Costa Rica
| Carolina Melisa Pinto and others | Journal of Environmental Management | 2024
Researchers combine multiple data sources to identify priority locations for wildlife-road mitigation in southwestern Costa Rica.
Do Wildlife Crossings Mitigate the Barrier Effect of Roads?
| Kylie Soanes and others | Journal of Applied Ecology | 2024
A large research synthesis finds that crossing structures commonly restore movement across roads, though population-level benefits are less consistently measured.
Wildlife Overpass Size, Distribution and Effectiveness
| Lauren Brennan and others | Frontiers in Ecology and Evolution | December 2022
Researchers review the dimensions, geographic distribution and ecological effectiveness of wildlife overpasses throughout the world.
Elephant Use of Railway Underpasses in Kenya
| Meshack Koskei and others | Global Ecology and Conservation | 2022
Researchers studied how elephants used 41 crossing structures along the standard-gauge railway through the Tsavo ecosystem.
Wildlife Use of Underpasses in Southern Kenya
| Francis Lala and others | Ecology and Evolution | April 2022
Monitoring found that species responded differently to crossing designs, with hyenas and leopards using underpasses more readily than giraffes and some antelope.
Placing Green Bridges Optimally With Habitat Cycles
| Maike Herkenrath and others | arXiv | January 28, 2022
The paper investigates mathematical methods for selecting affordable green-bridge networks that reconnect multiple species’ habitats.
Roads and Wildlife: A Global Review
| Various authors | Frontiers in Ecology and Evolution | 2021
The research reviews the global ecological effects of roads and the mitigation strategies available to transportation planners.
Placing Green Bridges Optimally: A Multivariate Analysis
| Till Fluschnik and Leon Kellerhals | arXiv | February 8, 2021
Researchers explore algorithmic approaches for connecting fragmented habitats with a low-cost network of green bridges.
Designing Wildlife Crossings for Ungulates in China
| Bin Zhang and others | Transportation Research | March 14, 2019
Researchers used field surveys and expert knowledge to propose underpass locations for ibex, argali and gazelles along a desert expressway.
Wildlife Habitat Connectivity Across European Highways
| Federal Highway Administration | FHWA | 2002–2015
A federal international study examines European standards, designs and research concerning wildlife crossings and green bridges.
Highway Mitigation Fencing Reduces Wildlife Collisions
| Anthony Clevenger and others | Ecological Applications | 2015
Research emphasizes that fencing and well-positioned crossing structures are most effective when designed as a coordinated system.
ARC International Wildlife-Crossing Design Competition
| ARC Solutions | ARC Solutions | 2010–2011
The competition brought architects, engineers and ecologists together to design an innovative wildlife bridge for Interstate 70 in Colorado.
Effects of Roads on Animal Abundance
| Lenore Fahrig and Trina Rytwinski | Ecology and Society | 2009
The review explains how traffic mortality, habitat loss, avoidance and reduced connectivity influence animal populations near roads.
Banff Wildlife Crossings Project Final Report
| Anthony Clevenger and others | Parks Canada | 2009
The report documents long-term research into wildlife movement, population connectivity and crossing effectiveness along the Trans-Canada Highway.
Wildlife-Vehicle Collision Reduction Study
| Federal Highway Administration | FHWA | 2008
The national study reviews wildlife-collision data and evaluates fencing, crossings, detection systems, signs and other countermeasures.
Wildlife-Vehicle Collision Reduction Report to Congress
| Federal Highway Administration | FHWA | 2008
The report documents the scale of wildlife collisions in the United States and recommends improved data, planning and mitigation.
The Bullwinkle Defense System
| Kristen Philipkoski | Wired | February 2002
Early animal-detection systems used infrared sensors and electronic warning signs to alert motorists when large wildlife approached highways.
Factors Influencing Wildlife-Underpass Effectiveness in Banff
| Anthony Clevenger and Nigel Waltho | Conservation Biology | 2000
Banff research showed that species respond differently to crossing dimensions, habitat cover, human activity and surrounding terrain.
Guides, Books, Toolkits and General Resources
Wildlife Crossings Pilot Program Fact Sheet
| Federal Highway Administration | FHWA | January 28, 2026
The federal fact sheet explains the statutory purpose, eligible activities and funding structure of the United States Wildlife Crossings Pilot Program.
Wildlife-Crossing Pilot Program Notice of Funding Opportunity
| Federal Highway Administration | FHWA | June 2024
The notice describes federal eligibility, selection criteria and application requirements for wildlife-crossing projects.
Wildlife-Crossing Pilot Program Grant Toolkit
| U.S. Department of Transportation | USDOT | June 6, 2024
The toolkit explains how rural governments, transportation agencies, tribes and other eligible entities can seek federal wildlife-crossing grants.
Crossings: How Road Ecology Is Shaping the Future of Our Planet
| Ben Goldfarb | W. W. Norton | September 12, 2023
Ben Goldfarb traces the ecological history of roads and examines attempts to reduce their effects on wildlife and natural systems.
Wildlife Crossings Pilot Program Overview
| Federal Highway Administration | FHWA | August 1, 2023
The program overview summarizes the goals and funding created under the Infrastructure Investment and Jobs Act.
Wildlife-Crossing Communications Toolkit
| Network for Landscape Conservation | Network for Landscape Conservation | 2021
The toolkit provides communication materials for organizations promoting wildlife crossings and transportation-related habitat connectivity.
Wildlife Crossings: Conservation-Media Toolbox
| Iowa State University | Institute for Transportation | 2018
The guide introduces crossing types, design considerations and examples involving animals ranging from amphibians to bears.
Handbook of Road Ecology
| Rodney van der Ree, Daniel Smith and Clara Grilo | Wiley | 2015
This international handbook summarizes research on road mortality, fragmentation, crossing design, monitoring and transportation policy.
Safe Passages: Highways, Wildlife and Habitat Connectivity
| Jon Beckmann and others | Island Press | 2010
The book examines scientific, engineering and policy approaches for maintaining wildlife movement across highways.
Road Ecology: Science and Solutions
| Richard Forman and others | Island Press | 2003
This foundational work established road ecology as a field examining the environmental effects of roads and possible solutions.
Wildlife Crossings Program
| Federal Highway Administration | FHWA | Current program
The federal program provides grants and technical information for projects that reduce wildlife collisions and improve terrestrial and aquatic connectivity.
Wildlife Crossings Pilot Program
| Federal Highway Administration | FHWA | Current program
The pilot program supports construction, engineering, planning, mapping, monitoring, fencing and other wildlife-road mitigation activities.
Wildlife Crossing
| Wikipedia contributors | Wikipedia | Current
This overview traces wildlife crossings from early European structures to modern overpasses, underpasses, canopy bridges and aquatic passages.
Wildlife Corridors Conservation Act
| Wildlands Network | Wildlands Network | Current
Federal corridor proposals seek to improve coordination between land conservation and transportation planning.
What Are Wildlife Crossings and How Do They Save Lives?
| World Wildlife Fund | WWF | Current
The explainer describes overpasses, underpasses, canopy bridges, tunnels and natural features that help animals avoid traffic.
Transportation and Wildlife
| U.S. Geological Survey | USGS | Current
USGS-supported studies investigate road mortality, animal movement and methods for identifying effective crossing locations.
Road Ecology and Endangered Species
| U.S. Fish and Wildlife Service | USFWS | Current
Wildlife crossings can support endangered-species recovery while improving safety for motorists.
Road Ecology
| Wikipedia contributors | Wikipedia | Current
Road ecology studies the effects of roads and traffic on animals, plants, water, habitat connectivity and ecosystem processes.
National Wildlife Corridors
| National Park Service | NPS | Current
Wildlife corridors connect seasonal ranges, breeding areas and climate refuges, often requiring safe passage across roads.
Habitat Connectivity and Transportation
| U.S. Forest Service | USDA Forest Service | Current
Forest Service research examines how transportation corridors fragment habitat and how crossings can restore ecological connections.
Ecological Connectivity and Climate Change
| The Nature Conservancy | The Nature Conservancy | Current
Connected landscapes allow wildlife to shift ranges in response to development, drought, fire and changing climate conditions.
Australia’s Wildlife-Crossing Handbook
| New South Wales Government | NSW Environment | Current
The guidelines explain how transportation projects can preserve animal movement through crossing structures, fencing and habitat design.
Organizations, Networks and Research Centers
Yellowstone to Yukon Wildlife Crossings
| Yellowstone to Yukon Conservation Initiative | Y2Y | Current
The program advocates for crossing projects that maintain wildlife movement across the northern Rocky Mountains.
Wildlife Crossings and Road Ecology Resources
| Kylie Soanes | Transport Ecology | Current
The site explains research on crossing effectiveness, habitat connectivity and the ecological consequences of transportation networks.
Western Transportation Institute Road Ecology Program
| Western Transportation Institute | Montana State University | Current
Researchers study animal detection, fencing, crossing design, monitoring and other approaches for reducing transportation impacts.
UC Davis Road Ecology Center
| University of California, Davis | Road Ecology Center | Current
The center conducts research on roadkill, wildlife movement, transportation planning and the effectiveness of mitigation projects.
The Future of Wildlife-Friendly Transportation
| ARC Solutions | ARC Solutions | Current
Design guides and case studies demonstrate how bridges, tunnels, culverts and fencing can be integrated into modern infrastructure.
International Conference on Ecology and Transportation
The conference presents research and case studies involving roads, railways, wildlife crossings and habitat connectivity.
Infrastructure and Ecology Network Europe
| Infrastructure and Ecology Network Europe | IENE | Current
The European network shares research, policy and practical guidance for making transportation infrastructure more compatible with biodiversity.
Freedom to Roam
| National Wildlife Federation | NWF | Current
Wildlife-corridor policy supports connected landscapes and transportation projects that allow animals to move safely.
Center for Large Landscape Conservation Road Ecology
| Center for Large Landscape Conservation | CLLC | Current
The program works with transportation agencies and communities to reduce wildlife collisions and reconnect large landscapes.
California Roadkill Observation System
| UC Davis Road Ecology Center | California Roadkill Observation System | Current
Public observations of wildlife collisions help researchers identify roadkill hotspots and potential crossing locations.
Brazilian Road Ecology Center
| Brazilian Center for Road Ecology | Universidade Federal de Lavras | Current
Brazilian road ecologists research wildlife mortality, crossing locations and mitigation measures across tropical landscapes.
Australasian Network for Ecology and Transportation
| Australasian Network for Ecology and Transportation | ANET | Current
The network connects researchers and practitioners working on wildlife crossings, road mortality and ecological infrastructure.
ARC Solutions Wildlife-Crossing Resources
| ARC Solutions | ARC Solutions | Current
ARC Solutions promotes research-based crossing designs that combine ecology, engineering, architecture and landscape planning.
General Wildlife-Crossing Coverage
How Road Ecology Is Shaping the Future of Our Planet
| Jenni Doering and Ben Goldfarb | Living on Earth | August 22, 2025
Journalist Ben Goldfarb discusses how roads alter ecosystems and how crossing structures can reconnect fragmented landscapes.
Wildlife Crossings Can Protect Migrating Animals
| Jennifer S. Holland | Pew Trust Magazine | June 10, 2020
Bridges, tunnels and fencing can protect migrating herds while reducing costly and dangerous vehicle collisions.
Keep It Wild: Interstate 80 Wildlife Overpass
| Utah Department of Transportation | UDOT | 2019
Utah’s Parleys Canyon overpass was constructed to help deer, elk, moose, bears and other animals cross Interstate 80 safely.
Green Bridges: Safer Travel for Wildlife
| Highways England | UK Government | July 31, 2015
Green bridges planted with local vegetation allow mammals, birds, insects and other organisms to move across major transportation corridors.
