Safe Passage

The I-40 Pigeon River Gorge Wildlife Crossing Project

I-40

Research results unveiled for Safe Passage project area, providing framework for wildlife–vehicle collision prevention

The burden imposed by I-40 on wildlife habitat connectivity and transportation safety makes the Pigeon River Gorge a national priority site for wildlife–vehicle collision mitigation.

On June 29, two partners of the Safe Passage Fund Coalition — Wildlands Network and the National Parks Conservation Association — released their official report, Road Ecology Research and Mitigation Strategies to Improve Wildlife Connectivity and Human Safety along I-40 in the Pigeon River Gorge.

The much-anticipated report details the findings of more than three years of roadside research in the I-40 Pigeon River Gorge project area combined with analysis of 20 years of historical data. The study was one of largest road ecology research projects ever completed in the eastern United States.

The report was authored by a team of cooperating researchers and scientists:

  • Liz Hillard – Ph.D., Senior Wildlife Biologist, Wildlands Network
  • Steve Goodman – Conservation Biologist, National Parks Conservation Association
  • Ron Sutherland – Ph.D., Chief Scientist, Wildlands Network
  • Jeff Hunter – Southeast Regional Program Manager, National Parks Conservation Association

Based on the research findings, the report provides 20 detailed mitigation recommendations for improvements to existing structures or creation of new structures throughout the Gorge, and calls for installation of a system of strategically placed wildlife fencing. Additionally, through consensus, the report’s authors provide seven “top priority” recommendations, including key opportunities to construct wildlife overpasses and install larger culverts under the highway.

Click here to read the executive summary of the report, and click here to read the report in full.

READ THE SUMMARY

The research provides the framework for mitigation strategies to both improve existing structures and construct new wildlife-specific structures to reduce wildlife–vehicle collisions (WVCs) and increase wildlife habitat connectivity.

Not just about the bears: Researchers consider mesocarnivore needs in Safe Passage study

By Steve Goodman, Volgenau Wildlife Research Fellow with National Parks Conservation Association & Co-research Lead for the Pigeon River Gorge Wildlife Connectivity Study

Though the target species of our Safe Passage research are black bear, elk and white-tailed deer — selected because they are relatively easy to monitor and are of the highest concern from a driver safety perspective — they’re not the only animals we’ve studied through this project.

We’ve also collected data on mesocarnivores, which are small to mid-sized mammals whose diets are mostly comprised of other animals, and we are assessing their needs for safe passage under Interstate 40 as well. Mesocarnivores in our study area include bobcats, coyotes, gray foxes, long-tailed weasels, otters, raccoons, red foxes and Eastern spotted skunks.

While improving safe passage for larger mammals should, in general, benefit smaller critters too, several mesocarnivores have very specific requirements that we also must consider when planning new structures or improving existing ones.

We also always work on increasing our understanding of the needs of even smaller animals — like frogs, salamanders and snakes — but that is for a future blog.

Through wildlife camera research in the Pigeon River Gorge, Safe Passage researchers have observed these mesocarnivore species (and more), just within the forested I-40 right-of-way.

In the News: Smoky Mountain Living interviews Safe Passage’s Jeff Hunter

In February 2022, Smoky Mountain Living magazine published “A Conversation With the Smokies’ Wildlife Crossing Guard,” an interview with Safe Passage facilitator and National Parks Conservation Association senior program manager Jeff Hunter.

In the article, Hunter spoke with reporter Holly Kays on wildlife crossings in the Smokies, as well as the work of Safe Passage: The I-40 Pigeon River Gorge Wildlife Crossing Project.

“Interstate 40 opened in the gorge in 1968, and at that time the bear population was probably a quarter of what it is today — if not less — and there were no elk on the landscape,” Hunter said in the interview. “Today we have a growing bear population and a growing elk population that’s on both sides of the highway.”

Hunter went on to describe the increase in mortality rates along this stretch of interstate, as well as the work being done to mitigate this increase, then added: “The park is big, but wildlife doesn’t recognize the boundaries. So we have to work outside the boundaries if we’re going to make an impact.”

To read the full interview in Smoky Mountain Living, click here.

NCDOT to begin construction on wildlife crossing at Harmon Den

The bridge over Harmon Den Road at Interstate 40 Exit 7. Photo courtesy of Google Maps Satellite imagery

On Nov. 3, 2021, the North Carolina Department of Transportation announced preparations for significant construction on Interstate 40 over Harmon Den Road, at Exit 7 in Haywood County. Starting as soon as Nov. 9, a contractor for the NCDOT will begin work to replace the bridge at this exit, integrating wildlife crossings into the new structure.

The Harmon Den area has long been a hotspot for wildlife-vehicle collisions, and Safe Passage: The I-40 Pigeon River Gorge Wildlife Crossing Project has advocated for building a wildlife crossing at this location. When the NCDOT announced plans to replace the existing bridge structure here, Safe Passage and its partners collaborated with the agency for a safe solution to fit this particular site.

The plans for the new Harmon Den bridge include two paths — one on each side of Cold Springs Creek — to help wildlife migrate from one side of the interstate to the other without encountering vehicles. A 9-foot tall fence will guide animals to the trails, away from traffic and under the bridge. 

NCDOT is also evaluating the use of wildlife guards — similar to slotted cattle guards — to prevent deer and elk from walking up the ramps. These measures will hopefully encourage wildlife to cross under the bridge and reduce the possibility of animal accidents. 

“We are excited to be adding protections for wildlife in this and other upcoming NCDOT projects,” said Division 14 Engineer Wanda Austin in a press release from the NCDOT. “We have worked with a wide variety of interest groups, transportation, and wildlife experts to incorporate these unique features to benefit the people who drive the gorge, and the animals that live in the gorge.”

Austin has been a participating stakeholder in the Safe Passage collaborative since its inception in 2017.

The traffic management plan for this project includes a six-month detour around the bridge, with drivers utilizing the exit and onramps. 

In late October and early November, construction crews from contractor Kiewit Infrastructure South have been mobilizing equipment and preparing to begin significant construction activities. By the first week of November, crews had already begun upgrading the exit and entrance ramps. 

As soon as mid-November, all traffic will be funneled into a one-lane pattern prior to the bridge and will use the ramps as a detour around the bridge. Traffic will remain in this pattern into May 2022 while crews remove and replace the deteriorating structure. 

In a feature article published by the Asheville Citizen Times on Nov. 5, Jeff Hunter, National Parks Conservation Association senior program manager and Safe Passage facilitator, thanks the NCDOT for its collaborative work to make I-40 a safer place for wildlife and motorists alike.

Black bears, elk, whitetail deer and other, smaller animals live in the surrounding mountains and naturally migrate across the area — and across the highway — looking for food, mates and habitat, Hunter told the Citizen Times.

In addition to the unique wildlife features, this five-bridge project is also the first of its kind in the state to be administered in a new method with the intent of forming a partnership between the NCDOT, the contractor and the design team. Kiewit Infrastructure earned the $19 million contract for the first of the five, which has a final completion date set in May 2024.

Exit 7 from I-40, where construction will soon begin to replace the existing bridge structure and add crossings for wildlife.

The current I-40 overpass as viewed from Harmon Den Road.

The result of the new construction manager/general contractor method is lower costs and expedited delivery from the first step in the design phase to the last inspection of the new bridge, and new safe passage underneath.

Drivers desiring to go from Asheville to Dandridge, Tenn., may choose to take I-26 West to Kingsport and then I-81 South to Dandridge. This route adds about 45 minutes to driving time compared to a typical trip through the gorge.

Do animals behave differently around busy roadways? Yes, observation shows.

Observations in the Safe Passage study area and beyond have begun to show that wild animals are keenly aware of the threats associated with roadways.

Safe Passage researchers have observed what appears to be heightened bear vigilance near the highway (see Figures 1A-1C). Researchers in other parts of the country have shown that GPS-collared black bears approaching roads, especially high-volume highways experience increased heart rates (Ditmer et al. 2018) and higher movement speeds (Zeller et al. 2020). 

Roads sometimes serve as barriers and, other times, as mortality traps. It is an ongoing practice in risk/reward evaluation — for food needs, breeding opportunities, etc. — that bears and other wildlife must make when traversing landscapes infused with roads.

Bears observe and approach Interstate 40 with caution

Figure 1A. An adult black bear observing Interstate 40 one hundred feet away.
Figure 1A. An adult black bear observing Interstate 40, from 100 feet away.
Figure 1B. A young black bear observing Interstate 40 one hundred feet away.
Figure 1B. A young black bear observing Interstate 40, from 100 feet away.
Figure 1C. Bear approaching and returning from Interstate 40 seventy feet to the right.
Figure 1C. Bear approaching and returning from Interstate 40, from 70 feet to the right.

Though data collection is not complete, near the highway, Safe Passage has so far observed fewer sows with cubs, fewer sibling-and-adult interactions and fewer of other normal behaviors. This sharply contrasts with observations made at a distance from the highway, where less stressful and less human-disturbed environments show bears being bears — playing or showing aggression, climbing trees and marking surroundings with their scent (see Figures 2A-2C). 

Farther from the highway, bears relax and play

Figure 2A. Bears wrestling in Great Smoky Mountains National Park two miles from Interstate 40.
Figure 2A. Bears wrestling in Great Smoky Mountains National Park two miles from Interstate 40.
Figure 2B. Adult male black bear sitting just before dusk 700 feet from Interstate 40.
Figure 2B. Adult male black bear sitting just before dusk 700 feet from Interstate 40.
Figure 2C. Juvenile black bear climbing tree 1000 feet from Interstate 40.
Figure 2C. Juvenile black bear climbing tree 1000 feet from Interstate 40.