Banff used 6 vegetated overpasses to curb highway wildlife collisions along 82km of road; the result transformed fragmented wilderness into connected animal corridors

Banff used 6 vegetated overpasses to curb highway wildlife collisions along 82km of road, creating a system designed to help animals move between habitats without entering the highway. The project began when the Trans-Canada Highway through Banff National Park was expanded from two lanes to four. Parks Canada combined fencing with wildlife underpasses and overpasses to reduce wildlife-vehicle collisions and maintain habitat connections. Today, the system has six overpasses and 38 underpasses, while fencing covers 82 km of highway. Research has recorded more than 200,000 crossings by 11 species of large mammals. The project has also become a reference for wildlife crossing work in other countries.

Banff used 6 vegetated overpasses to curb highway wildlife collisions along 82km of road as part of a wider effort to reduce the effects of roads on animals. The Trans-Canada Highway passes through Banff National Park and divides areas used by wildlife.

From the highway, one of the structures can look like a concrete bridge. The top, however, contains soil, grass, trees and wildflowers. Fencing along the highway directs animals toward these crossings and keeps them away from the road.


Parks Canada human-wildlife conflict specialist Steve Michel said the overpasses have been effective for wildlife. The highway system also includes underpasses, with different animals using different types of crossings.

Why Banff needed wildlife crossings?

The Canadian government has spent more than $400 million since the 1980s on upgrading and twinning the four-lane highway. About one-quarter of that budget was set aside for projects intended to reduce wildlife collisions.

Parks Canada planned to fence roughly 180 km of highway and build several dozen wildlife crossing structures. The aim was to reduce animal deaths caused by vehicles while allowing animals to continue moving between habitats.

The crossing system was developed around two main measures:

• Install fencing on both sides of the twinned highway.
• Build wildlife underpasses and overpasses to connect habitats.
• Track animal movement through the structures.
• Use research findings to improve later highway construction phases.

Wildlife movement research in Banff has continued since 1996. Parks Canada describes the monitoring program as the longest-running wildlife crossing research and monitoring program in the world.

Banff’s overpasses changed views after early criticism

The first wildlife overpass in Banff was completed 20 years before the source material marked its anniversary. At the time, the idea faced opposition. Tony Clevenger, who studied the crossing structures for the Western Transportation Institute, said the project initially received criticism. Local newspaper editorials questioned the cost and suggested animals would not use the bridges. The structures cost between $2 million and $3 million each.

There were also concerns about how predators and prey would behave around the fences. Some people believed wolves could drive prey toward the barriers. Clevenger said several years of data and research published in peer-reviewed journals helped change public views about the crossings.

What the research found?

The monitoring program produced data on how animals use the structures. Clevenger's research covered 17 years and found that mortality among large carnivores was 50 to 100 per cent lower on highway sections with overpasses and underpasses.

Elk deaths also fell in these sections. Their mortality rate was close to zero compared with about 100 elk-vehicle collisions per year in the mid-1990s. Researchers recorded 11 species of large mammals using the crossing structures more than 200,000 times.

The recorded users included:

• Black bears
• Grizzly bears
• Elk
• Red foxes
• Hoary marmots
• Boreal toads
• Wolverines
• Lynx
• Garter snakes
• Beavers
• Mountain lions

The crossings therefore became useful for animals beyond the species initially considered in the planning process.

How different animals use the structures?

The crossings are not used by every species in the same way. Michel explained that black bears and mountain lions use underpasses. These structures provide tunnels with limited light and moisture. Grizzlies and ungulates, meanwhile, tend to use overpasses because they provide open sightlines. The design of a crossing can therefore affect whether an animal chooses to use it.

The system has a total of 44 crossing structures. These include six overpasses and 38 underpasses. Banff also has 82 km of highway fencing connected with the wildlife crossing system. Parks Canada says this combination gives Banff the largest concentration of wildlife crossing structures and highway enclosure fencing at one location.

Grizzly crossings also support genetic connection

The impact of the crossings extends beyond preventing vehicle deaths. A 2014 Montana State University study found that grizzly bears were using the structures often enough to help maintain genetic connection between bear populations on opposite sides of the highway.

The highway could otherwise divide populations and reduce movement between them. Regular crossings allowed bears to move across the road and helped prevent the populations from becoming genetically isolated. This finding added another part to the research around wildlife corridors. A crossing can help an animal survive a road and also allow movement between habitats.

The Banff model has reached other countries

Researchers and government representatives from other regions have visited Banff to study its wildlife crossing system. In the 2000s, Salish and Kootenai tribal delegations from Montana visited the park to study grizzly bear use of the overpasses and develop ideas for crossings on the Flathead Reservation.

Biologists from Washington's Cascade Range later examined the system while working on a wildlife crossing project over Interstate 90. Delegations have since come from countries including Mongolia, Argentina and China. Ament recalled a Chinese delegation studying the work of Clevenger and taking notes during his presentation.

Mongolia has also developed policy standards requiring wildlife passage along certain automobile and railway routes in the eastern steppe and Gobi Desert. Plans are being developed for a wildlife crossing in the Gobi to help species including goitered gazelle, black-tailed gazelle and argali bighorn sheep.

Roads can divide habitats even when animals avoid collisions

The issue goes beyond animals being hit by vehicles. Roads can divide habitats and block migration routes. The source material estimates that 25 million kilometres of new roads could be built by 2050, with much of the construction expected in developing countries.

Rob Ament of Montana State University's Western Transportation Institute said many of these roads will enter biodiversity hotspots. Countries building new roads may therefore need to address wildlife movement while infrastructure is being developed. Banff provides information about how crossings can work for species found in the Canadian Rockies. Other regions face different questions.

Researchers need to determine what type of crossing a monkey might use, how large a tunnel should be for a jaguar and how to encourage tapirs in Belize to use crossings. Tapirs can weigh about 230 kilograms and have been killed on roads. The experience in Banff has therefore provided a starting point, while other countries must adapt crossing designs to their own species and landscapes.

The railway remains a separate challenge

While wildlife deaths on the Trans-Canada Highway declined, the Canadian Pacific Railway corridor through Banff presented another problem. In 2010, Parks Canada and CP Rail began a $1 million, five-year study after animals, including grizzlies, were dying on the railway in increasing numbers.

Researchers identified several factors that drew animals toward the railway. These included vegetation and difficulty detecting approaching trains. Bears were sometimes found moving toward trains instead of away from them. The study concluded that there was no single solution to the railway problem. Overpasses could be possible at some locations.

The situation is more difficult because the railway is privately owned. Wildlife managers cannot introduce crossing structures over the tracks in the same way they could on publicly controlled infrastructure. The source also notes that China has built 33 wildlife passages over and under the Qinghai-Tibet Railway to help Tibetan antelope during migration.

Why the Banff project matters for future roads?

Banff has highways and railway lines carrying vehicles and trains through a national park. That creates a combination of infrastructure and wildlife challenges that many protected areas do not face. The research from Banff has provided evidence that wildlife crossings can reduce highway collisions and maintain animal movement.

Parks Canada says continuous research since 1996 has helped improve later stages of the Trans-Canada Highway Twinning Project. The agency has worked with the Western Transportation Institute at Montana State University, the Miistakis Institute of the Rockies, and the Woodcock and Wilburforce Foundations on research and monitoring.

The project shows how fencing, overpasses, underpasses and long-term monitoring can be combined when roads pass through wildlife habitat. It also shows why crossing designs need to be studied for the species and landscape where they will be built.

As more roads are planned around the world, the experience from Banff provides research and engineering information that other regions can use when planning ways to keep wildlife connected to its habitat.