Wildlife and Ecosystems

The Arizona Department of Transportation recently highlighted the benefits of its collaboration with the Arizona Game & Fish Department (AZGFD) to reduce elk-vehicle crashes on northbound I-17 south of Flagstaff in a blog post.

[Above photo by Arizona DOT]

In 2011, AZGFD noted a high number of elk-vehicle crashes occurred along a stretch of I-17 near Munds Park.  Because a full-grown bull elk can weigh upwards of 700 pounds, crashing into something that large can destroy a vehicle and cause serious injury or death to vehicle occupants, as well as the animal. 

In 2012, after a series of studies, AZGFD and the Arizona DOT installed ungulate – “ungulate” means “hoofed mammal” – fencing in four locations near Munds Park on I-17. In most instances, Arizona DOT works crews modified existing right-of-way fences with bolts and barbed wire, eliminating the need for completely new fencing and poles.

This project produced almost immediate results, both agencies said. From the 20 documented elk-vehicle crashes that occurred along this strip of I-17 from 2007 to 2010, only one occurred between 2010 and 2014.

Arizona DOT said this is but one example of the state mitigating wildlife issues through partnerships among multiple agencies. The agency noted it also collaborated with AZGFD to construct wildlife underpasses and elk crossings along State Route 260 east of Payson and desert bighorn sheep overpasses near historic Hoover Dam on US 93.

The wildlife protection efforts undertaken by Arizona DOT are reflective of similar initiatives spearheaded by state departments of transportation nationwide.

For example, in July and August every year, the North Carolina Department of Transportation temporarily lowers speed limits from 55 mph to 20 mph on the William B. Umstead Bridge – locally known as the old Manns Harbor Bridge – at dusk and dawn during the roosting period of purple martin bird flocks.

NCDOT noted in a statement that it has collaborated with the Coastal Carolina Purple Martin Society since 2007 to educate the public about the purple martin flocks, to protect both the birds and motorists.

Meanwhile, the Colorado Department of Transportation recently completed the state’s newest wildlife overpass and underpass on U.S. Highway 160 in the southwestern part of the state, celebrating the accomplishment with a ribbon-cutting event.

To date, Colorado DOT said it has built more than 60 wildlife mitigation structures crossing above or under highways throughout the state. Additionally, it has installed 400 miles of high big game fencing along state and U.S. highways or next to the interstates.

On the research front, a report released by an international pool funded study led by the Nevada Department of Transportation in July provides an “authoritative review” of the most effective measures to reduce animal-vehicle collisions, improve motorist safety, and build safer wildlife crossings.

With as many as two million collisions with large mammals in the United States leading to approximately 200 human deaths every year, the review compiled, evaluated, and synthesized studies, scientific reports, journal articles, technical papers, and other publications from within the United States and beyond to determine effectiveness of 30 different mitigation measures.

Ultimately, the report provides best management practices to reduce animal-vehicle collisions, increase habitat connectivity, and implement cost-effective solutions, Nevada DOT said.

As the Arizona Department of Transportation starts work on the  I-17 Improvement Project from Anthem Way to Sunset Point, it is taking steps protect the natural landscape along this stretch of scenic highway corridor as well. 

[Above photo by the Arizona DOT]

The agency said its work crews are removing native vegetation – including saguaros, palo verde trees and ocotillos – from the 23-mile project corridor to temporary nurseries, before eventually replanting them alongside an improved and wider highway. 

Drivers who regularly travel I-17 between Anthem Way and Sunset Point may see some of what the Arizona DOT describes as “plant salvage” work during the next several months. Plant salvage crews from the Kiewit-Fann Joint Venture developer team will collect hundreds of viable native trees, “accents” (such as ocotillos and yuccas), saguaros and other cacti from the construction area. Altogether, roughly two-thirds of the right-of-way along the 23-mile project area will remain undisturbed, meaning no plant salvaging will be necessary.

“October is usually the prime time for salvaging the plant material, just because our temperature is not too hot and not too cold,” said David Casselbury, a landscape architect with Arizona DOT, in a statement. “We’re hoping the general public will enjoy driving along the highway and seeing this plant material back in its natural environment once the project is complete.” 

The salvaged trees and cacti are not the only plants returning to the natural landscape once the improvement project is finished, the agency added, as it plans to add native seed mixes and nursery-grown plants to the highway construction area. Those efforts help to achieve the long-term goal of successfully revegetating areas within the construction area considered “landscape-able” with a mix of plants that will thrive and restore the natural environment for years to come. 

Restoring native plants has been an integral part of many Arizona DOT projects for more than 35 years, according to the agency.

For example, Arizona DOT spent the last four years relocating a rare and endangered species of cactus growing near the Pinto Creek bridge replacement project along U.S. 60 near Globe-Miami. Initiated in 2018, this relocation effort is the latest step in a long-term partnership between the Arizona DOT and the Desert Botanical Garden in Phoenix to protect hedgehog cactuses that only grow in one tiny area of the state.

The agency also relies on ‘biomonitor’ teams from Northern Arizona University or NAU to help its work crews find and relocate endangered species – including snakes, birds and fish – from construction sites.

Specifically, those biomonitor teams train construction workers and other involved in transportation projects to identify any endangered species and what to do if they come across one. The teams also monitor construction activity and help safely remove any endangered species out of harm’s way.

The Colorado Department of Transportation recently began work on the I-70 Genesee wildlife-crossing project, one of several I-70 Floyd Hill projects to improve both highway safety and traffic flow ahead of construction on the $700 million main project.

[Above image by Colorado DOT]

The I-70 Genesee wildlife-crossing project consists of a dedicated wildlife underpass going under I-70 between the exits for Lookout Mountain and Genesee. Additionally, crews will place wildlife fencing along both east and westbound I-70 that extends from the Genesee Exit to the Lookout Mountain Exit.

The agency noted that this area has the highest number of wildlife-vehicle collisions on the I-70 Mountain Corridor east of the Eisenhower-Johnson Memorial Tunnel.

“The new underpass at I-70 Genesee is the first major wildlife crossing to be constructed along the I-70 Mountain Corridor, and it will allow wildlife to safely cross underneath the interstate at a location which has historically been a hotspot for wildlife related crashes,” said Colorado DOT Executive Director Shoshana Lew in a statement.

“Reducing animal-vehicle conflicts and improving wildlife connectivity is a major element to the overall improvement of travel time reliability, safety, and mobility in the I-70 Floyd Hill project area,” she added.

The plan calls for construction of two new I-70 bridges, followed by excavation under those bridges to create the wildlife underpass. Once the underpass is complete, crews will install the wildlife fencing. Altogether, bridge and underpass construction should wrap up by the spring of 2024.

To date, Colorado DOT has built more than 60 wildlife mitigation structures crossing above or under highways throughout the state. Additionally, it has installed 400 miles of high big game fencing along state and U.S. highways or next to the interstates.

In August, the agency completed the state’s newest wildlife overpass and underpass on U.S. Highway 160 in the southwestern part of the state.

In October 2021, Colorado DOT and the Colorado Parks and Wildlife agency completed wildlife underpasses along a rural stretch of Interstate 25 between Colorado’s two largest cities, Denver and Colorado Springs.

That wildlife mitigation system is part of a $419 million transportation improvement project – known as the I-25 South Gap project – that aims to improve safety and travel on 18 miles of I-25 south of the Denver metropolitan region; a route that more than 87,000 motorists use on a daily basis.

Key initial components of the $700 million I-70 Floyd Hill project kicked off recently by the Colorado Department of Transportation include the construction of wildlife crossings and fences as well as a “mobility hub” to provide transit and electric vehicle services.

[Above photo by the Colorado DOT]

The project will rebuild a seven-mile stretch of I-70 from exit 248 northwest of Evergreen to exit 241 in eastern Idaho Springs and work to eliminate a bottleneck on one of the most congested stretches of the I-70 Mountain Corridor.

Early construction begins this fall with a new wildlife crossing at Genesee and roundabouts along US 40 between Evergreen and Floyd Hill, with major construction on the corridor starting in spring 2023.

“The I-70 Floyd Hill Project will improve travel time, reliability, and safety,” explained Shoshana Lew, executive director of the Colorado DOT, in a statement.

“By eliminating the bottleneck at Floyd Hill, the project will significantly ease congestion and decrease the number and severity of crashes through more consistent traffic flow and speeds,” she said. “The project will provide alternate emergency access through a newly connected frontage road system that strengthens safety and mobility for thousands of Coloradans that rely on I-70 to access their communities and for the millions who visit the mountains annually. Essential to this project are multi-modal options, including our Pegasus van service which already started last spring, and improvements to the Greenway trail for pedestrians and cyclists to enjoy Clear Creek County.”

Key wildlife and environmental improvements involved in the I-70 Floyd Hill project include:

• Improving the multimodal Greenway trail.
• Building wildlife crossings and fencing, and restoring nearby creek and riparian areas to protect and preserve the local environment and wildlife.
• Developing a mobility hub with electric vehicle infrastructure and accessibility options that integrate into the state’s I-70 transit service, including the new Pegasus van service added in May 2022 to the corridor.
• Providing permanent air quality monitors and coordinating rural broadband access with local communities.

Across the country, state departments of transportation provide support to a wide variety of efforts aimed at supporting numerous bird species and their habitats.

[Above photo by the NCDOT]

For example, in July and August every year, the North Carolina Department of Transportation temporarily lower speed limits from 55 mph to 20 mph on the William B. Umstead Bridge – locally known as the old Manns Harbor Bridge – at dusk and dawn during the roosting period of purple martin bird flocks.

NCDOT noted in a statement that it has collaborated with the Coastal Carolina Purple Martin Society since 2007 to educate the public about the purple martin flocks, to protect both the birds and motorists. From late July through August, the west end of the bridge becomes home to as many as 100,000 purple martins as they prepare for their annual migration to Brazil. The birds roost under the bridge at night, departing at dawn to feed and returning at sunset. The flock is so large during its peak that it is visible on radar.

To protect those birds, NCDOT activates flashing lights and lowers the speed limit on the bridge at sunrise and sunset. Law enforcement monitors speed limits on the bridge to allow motorists and birds safe passage across the sound. Since NCDOT installed those lights and lowered speed limits, the Coastal Carolina Purple Martin Society has seen a dramatic decline in bird deaths around the bridge.

On a broader basis, NCDOT initiated a mitigation program in April operated by its Division of Aviation to reduce the risk of wildlife hazards by providing a variety of training and support options for both airports and aircraft.

The agency said North Carolina airports average at least one bird or other wildlife strikes upon aircraft per day, which can cause significant damage. For example, in 2018, an aircraft landing at a general aviation airport sustained more than $800,000 in damage when it struck two of six white-tailed deer crossing the runway.

“Flocks of birds taking flight, deer crossing runways, and other such hazards can cause serious damage to property and even loss of life,” noted Rajendra Kondapalli, the program’s manager, in a statement. “Our program focuses on reducing that risk and increasing safety for aircraft that fly in and out of airports across our state.”

Meanwhile, the Idaho Transportation Department helped Girl Scout Troop 1806 and the Idaho Department of Fish and Game (IDFG) install homemade birdhouses near the US-95 McArthur Lake project south of Naples.

ITD Project Manager Carrie Ann Hewitt has consulted IDFG biologists through the design of the project, which includes realigning one mile of the highway near the lake to make the existing curves safer for drivers and to elevate the highway where it dips down to the water. Elevating US-95 will also allow wildlife to pass underneath to access the IDFG McArthur Lake Wildlife Management Area, ITD noted in a statement.

The agency expects to start construction on this roadway project in 2023 and 2024, with tree thinning starting in 2022 to prepare for the road’s realignment.

Hewitt – a co-leader for the Girl Scout troop – has been researching the habitat needs of the mountain bluebird, flocks of which reside near the project, and reached out to IDFG to see about improving its habitat.

“Mountain bluebird populations are struggling,” Hewitt noted. “The girls found that cowbirds actually swap out eggs with the bluebirds, and the bluebirds unknowingly hatch the wrong offspring.”

The troop built 18 birdhouses with entrances too small for the cowbirds to prevent that from happening, with IDFG suggesting that they install them near McArthur Lake due to the recent thinning, along with another site near Boundary Creek.

A research document just released by an international pool-funded study led by the Nevada Department of Transportation provides an “authoritative review” of the most effective measures to reduce animal-vehicle collisions, improve motorist safety, and build safer wildlife crossings.  

[Above image by the Nevada DOT]
With as many as two million collisions with large mammals in the United States leading to approximately 200 human deaths every year, the review compiled, evaluated, and synthesized studies, scientific reports, journal articles, technical papers, and other publications from within the United States and beyond to determine the effectiveness of 30 different mitigation measures.

Ultimately, the report provides best management practices to reduce animal-vehicle collisions, increase habitat connectivity, and implement cost-effective solutions. Key findings include:

• The most proven effective measures to reduce animal-vehicle collisions by over 85 percent while providing habitat connectivity remain wildlife fences in combination with wildlife overpasses and/or underpasses. Researchers now know that these measures must cover at least several miles to reduce collisions significantly with large mammal species.
• Traditional warning signs, educational campaigns, reducing posted nighttime speed limits, and other measures are in general less than 50 percent effective. Some mitigation measures are at least 50 percent or greater effective in reducing animal-vehicle collisions, including roadside animal detection systems, nighttime lighting, and reducing the size of the population of wildlife species involved. However, none of those reduces a road’s “barrier effect” for wildlife; some even increase the barrier effect.  
• No detailed study examines the ability to reduce animal-vehicle collisions with vehicle-based detection technology in highway situations – especially where connected and autonomous vehicles or CAVs are concerned. While there are likely benefits of this technology for reducing collisions with large mammal species, the sensors typically do not detect smaller species. Furthermore, this technology does not reduce the barrier effect of the road and traffic for wildlife.

Nova Simpson, a biological supervisor and large mammal mitigation specialist with Nevada DOT, helped manage the study.  Simpson believes it will help state and federal transportation, land management, and wildlife agencies optimize efforts to reduce animal-vehicle collisions. 

“This pooled fund study provides a very unique opportunity to synthesize current knowledge from the U.S., Canada, and internationally,” noted Simpson in a statement. “It will improve the cost-benefit analyses of mitigation measures, field test improved designs and technologies; and coordinate and provide outreach to transportation, land management, and wildlife agencies and their stakeholders. Ultimately, these efforts will help in the reduction of wildlife-vehicle collisions across the United States.”
Nevada DOT has already installed many roadway improvements to reduce potentially dangerous animal-vehicle collisions statewide. For example, in February, the agency installed four-foot high livestock fencing along stretches of U.S. 50 between State Route 341 and Chaves Road in Dayton, NV, to reduce horse-vehicle collisions.

Nevada DOT also worked with the Nevada Department of Wildlife to install nine safety crossings on Interstate 80 between Wendover and Wells and U.S. 93 north of Wells in the northeastern portion of the state four years ago.

That project – which garnered a 2019 Environmental Excellence Award from the Federal Highway Administration – covered wildlife overpasses with native soil and vegetation to replicate the natural environment, with roughly 60 miles of eight-foot-high fencing installed along both sections of the roadways redirecting and encouraging deer, mules, and other animals to use the crossing points.

The agency added that it has also installed 400 miles of tortoise fencing and 19 tortoise underpass/culvert crossings on the U.S. 95 and U.S. 93 in southern Nevada to reduce wildlife-vehicle collisions and tortoise road mortality.