Frequently Asked Questions

Why are driver-safe highway crossings necessary?

We are lucky to live in a wildlife-rich area. Sadly, wildlife-vehicle collisions have increased sharply, as both traffic and wildlife populations have increased. In fact, wildlife-traffic collisions have increased 50 percent nationwide in the past 15 years. Every collision with a deer, elk, moose, or bison does thousands of dollars of damage to vehicles and endangers the lives of innocent people.

Do driver-safe highway crossings work?

Yes! Idaho engineers know how to address this problem. Across Idaho, Wyoming, Montana and Canada, driver-safe wildlife crossings have PROVEN to reduce wildlife-vehicle collisions by as much as 90 percent. What’s more, these features pay for themselves over time in saved money from avoided accidents.

Are there cheaper alternatives? Like slower speed limits?

No. Unfortunately, alternatives like flashing lights, wildlife detections systems and highway signs are proven NOT to be adequately effective. Truckers and motorists will drive highway speeds on highways, even if posted lower. We need to let Idaho highway engineers do their job and build us a modern US 20. You cannot put a price tag on the life of a loved-one. 

Who pays for building and maintaining these structures?

Modern, driver-safe wildlife crossings typically account for 10 percent of the entire highway modernization project. They are paid for by federal fuel taxes, which are already collected for this purpose. When crossings are built with road construction, the Federal Highway Administration pays for 93% of total project costs. This is the best time to add driver-safe crossings, as costs are kept to a minimum. Many crossings are added to modernize road systems without additional road construction. In some cases, there are strong private- public partnerships that are paid for without any use of Federal or state transportation funds. 

It’s important to understand that county taxpayers do NOT pay for these highway improvements or for maintaining them.

Will the crossings be unsightly?

Beauty is in the eye of the beholder, but we can all agree that road-killed wildlife carcasses and smashed cars are ugly. Professional engineers and landscape architects design tunnels and fencing are designed for minimal visual impact. Fencing is minimal necessary to do the job – usually about 8 feet tall and ONLY where necessary.

Will fencing keep people off public lands or limit hunting opportunities?

No. The Forest Service, Idaho Department of Transportation and Idaho Fish and Game all agree that access to public land is paramount and preserving legal, appropriate access for snowmobiles, ATVs, stock and others will be built into the engineering plan. We all value the freedom to enjoy our public land.

Will driver-safe wildlife crossings impact property values?

Driver-safe wildlife crossings have been built across the West and there has been no corresponding change in property values. In fact, realtors report people shopping for rural property want to live harmoniously with the local wildlife and value a safe, modern highway.

Aren’t big rigs the ones doing the most damage to our wildlife?

Probably. Highway 20 is a major freight route, so we see many collisions between semis and wildlife. Still, passenger cars are also involved in many wildlife collisions. That’s another reason to build a modern highway that is safe for motorists and wildlife alike.

Will overpasses will funnel animals for predators?

Biologists in other states say this is not a problem. Wildlife usually keep moving near narrow pinch points, preventing significant increases in predation. Studies have looked at wildlife crossings worldwide and found no significant changes in predation patterns. 

Beware wild exaggerations and misinformation

Unfortunately, we are seeing wildly inaccurate information about the costs of the project, the extent of fencing, and other claims. Please inform yourself before voting. If you have questions, please contact us on the contact page.

Island Park Driver-Safe Wildlife Passage Initiative

And the Fremont County Advisory Vote on Driver-Safe Wildlife Crossings

(Access the full primer with citations and maps here.)

US 20 is a two lane highway that runs parallel to the western boundary of Yellowstone National Park. As the primary access to Yellowstone National Park from Salt Lake City and Idaho Falls, US 20 is travelled by more than 1.5 million motorists annually, and travel is expected to grow to 2.5 million motorists annually by 2040. The Federal Highway Administration and the Idaho Transportation Department have proposed vast expansions of this highway over the next seven years. In an effort to increase driver safety and to protect priority migrations of wildlife in the Yellowstone Highlands, the Island Park Safe Wildlife Passage Initiative has advocated for wildlife mitigation to be integrated into the highway expansion. This initiative has been a grassroots partnership between Island Park residents supported by local conservation organizations. 

Based on local research, expert recommendations, and best available science, wildlife crossings are a proven, cost-effective solution to keep drivers safe and to aid wildlife migration in heavily travelled areas. 

Crossings keep motorists safe and keep wildlife connected. Crossings allow for wildlife to migrate, uninhibited by roads and traffic. Every state around Idaho has implemented successful crossings, including Nevada, Utah, and Wyoming. Elsewhere in the world, these structures have reduced wildlife accidents by up to 90%. Because crossings have a lifespan of 75 years, they are less expensive than animal detection systems. They are also more effective than automobile detection systems, fencing alone, reducing speed limits, or cutting back trees. 

Faced with both local support and opposition, Fremont County residents will be asked through an advisory vote if they support or object to wildlife crossings and associated fencing in November 2018.


Migration through Island Park

Two major elk herds cross over US 20 – the Madison River/Ennis, MT herd and the Sand Creek herd that winters near St. Anthony, ID. Island Park is a home to a resident moose population, a migrating mule deer population, and a migrating moose population – this is the largest migrating herd of moose in North America, which winters on the Sand Creek Desert near St. Anthony. 

According to the Idaho Department of Fish and Game, the Sand Creek migration for elk, moose, and deer is one of the top five most important migrations in the state. Idaho Department of Fish and Game also acknowledges that US 20 is the largest threat to this migration.  

The map below shows, individual collared elk in the Sand Creek herd. Their tracked movements demonstrate the impacts of how roads impede their natural seasonal movements. Roadkill data from September 2017 to September 2018 found more than 170 large mammals, primarily elk, mule deer, and moose, were hit by cars on US 20 through Island Park. Across the High Divide region, Island Park is one of the most important places for ecological connectivity for all local wildlife. In addition to hundreds of elk, moose, and mule deer, drivers have recently hit and killed two grizzly bears, one bison, two mountain lions and two wolves.


The Idaho Transportation Department, Idaho Department of Fish and Game, and the Wildlife Conservation Society completed a hotspot analysis on US 20 for elk and moose, which identifies the most common places for wildlife vehicle collisions and the most important wildlife crossings on US 20. Further, Idaho Transportation Department contracted a world-renowned road ecologist to identify an array of recommendations to reduce wildlife vehicle collisions and create a safer road for motorists. The study identified structures and design features that could make US 20 safer, but the recommendations were not adopted by the Idaho Transportation Department.

While nationally, only 5% of all accidents are wildlife collisions, 20% of all accidents in Island Park are wildlife collisions, and 36% of all collisions on Targhee Pass are wildlife collisions.  Traffic increased 30% between 2006 and 2016 on US 20 to 1.5 million vehicles per year, and is expected to increase to almost 2.5 million vehicles per year by 2040. When roads get  wider and faster with more traffic, wildlife vehicle collisions are known to increase, making animal crossings more difficult or even stopping them along historic migrations. If big game can’t make it across roads, the long-term viability of herds is at risk, as recent studies find that migration routes are learned from other animals in a herd.

Expansion of US 20

To accommodate more traffic from a growing residential population in the area and visitation to Yellowstone National Park, along with increased freight from Idaho Falls up to Bozeman and I-90, Idaho Transportation Department plans to widen the highway for much of the 40 mile stretch through Island Park. With $197.4 million in highway projects Chester to the Montana State Line, wider highways and increased traffic could affect long-term population viability of elk and moose herds if migration corridors are blocked. 

The Idaho Transportation Department’s first expansion project on US 20 is Targhee Pass near the Montana State Line. This is home to a resident moose population and where a spot the Madison River elk herd crosses each spring and fall years as they head from Yellowstone toward Ennis, Montana. The Idaho Transportation Department plans to widen, straighten, and add a truck passing lane to this four-mile section of road located north of Henry’s Lake to the Montana state line. The Idaho Transportation Department is currently completing an environmental assessment on this project. Alternatives and more resources can be viewed on the Idaho Transportation Department’s US 20 website. They are studying five options: a no-build option, one with animal detection systems, one that widens the road and includes advisory speed limit/variable message boards during migration, and two with overpasses.

Future US 20 Projects

Targhee Pass is the first of a series of highway expansion projects through Island Park in the next five to seven years. Idaho Department of Transportation has estimated more than $109 million for these expansions, many of which are in known hotspots for ungulates — deer, pronghorn, moose and elk — moving through Island Park. 

Idaho Department of Fish and Game has prioritized Targhee Pass, Harriman State Park, and Ashton Hill as the top locations in need of wildlife crossings.

Island Park Safe Wildlife Passage partners have long advocated for Idaho Department of Transportation to implement wildlife mitigations on the following projects as the design and construct an expanded US 20, but at this time the Idaho Transportation Department is not proposing any wildlife crossings along US 20, as they don’t believe it’s their responsibility to address. By taking connectivity and wildlife into account now, we could avoid the unnecessary loss of important wildlife and reduction to our hunting and recreation economy. 

Wildlife Crossings in the Crosshairs

After announcing the study of wildlife crossings and associated fencing on Targhee Pass, a vocal in Island Park worked to convince the public and decision makers that wildlife crossings aren’t in Island Park’s interest, spreading fear of losing access to public lands, reduced property values, and loss of business. As a result, Fremont County Commissioners agreed to put an advisory vote to the Fremont County voters on November 6, 2018.

While this is an advisory vote that is non-binding for the county, this vote is important. Advisory votes are counties’ efforts to have local influence over the management of federal lands, processes, and funding. Without local support, federal and state investments in wildlife will be diverted to more politically friendly places in the state or nation. Idaho has an opportunity to attract federal and private funds if it chooses to build modern, safe, and highways that protect wildlife migration. 

Public Lands Access and Hunting Regulations

The Caribou Targhee National Forest and Idaho Department of Fish and Game have supported the study of wildlife crossings in areas that are critical for the safety of humans and the well-being of wildlife. But both agencies have also been clear with the public and the Idaho Transportation Department that they are not open to changing public access or hunting regulations. Liz Davy, Island Park District Ranger, has publicly stated that the Caribou Targhee National Forest would not revisit travel plans, and therefore require that all public access, including all legal roads and trails, remain open with any plans of highway expansion. Similarly, Idaho Department of Fish and Game Regional Supervisor Jim White has public stated that the agency would not change hunting regulations in Island Park because of proposed wildlife crossings.

Map of Elk Migrations in the Greater Yellowstone Ecosystem.

Map of Elk Migrations in the Greater Yellowstone Ecosystem.