June 26, 2026 · Tags: wildlife, conservation, infrastructure, arizona, good-news
On a 17-mile stretch of highway in central Arizona, something remarkable happened: elk stopped dying.
State Route 260 cuts through the ponderosa pine forests between Payson and the Mogollon Rim. Before it was widened in the early 2000s, it was a winding two-lane road. The reconstruction turned it into a four-lane divided highway — faster, wider, and far more dangerous for the elk herds that had crossed this corridor for millennia. During construction, elk-vehicle collisions nearly tripled.
Then the fences went up. And the underpasses. And within a few years, elk-vehicle collisions dropped by more than 80%.
Arizona has spent the two decades since turning that first success into a statewide program. As of 2026, the state has more than 20 wildlife corridors — overpasses, underpasses, and fencing systems — strung across its highways. The newest, the I-17 Willard Springs Wildlife Overpass south of Flagstaff, is a 100-foot-wide concrete bridge spanning all four lanes of the interstate, flanked by eight miles of ungulate-proof fencing and wildlife escape ramps. Construction began in spring 2025. It's scheduled to open this fall.
The results across the network are striking. KNAU reports an average 90% drop in wildlife-related accidents where these corridors are installed. On SR 260 alone, the economic benefit from avoided collisions has averaged $2 million per year.
The Scale of the Problem #
The numbers on roadkill in the United States are staggering, and they've held steady for decades. The Federal Highway Administration's 2008 report to Congress — still the most widely cited source — estimates that 365 million vertebrate animals are killed by vehicles on U.S. roads every year. That's birds, mammals, reptiles, and amphibians. A million a day.
Of those, between one and two million are large animals: deer, elk, moose. State Farm's 2024–2025 claims data puts the insurance tally at 1.7 million animal collision claims in a single year, about 1.1 million of which involve deer. Around 200 people die in these crashes annually. Another 26,000 are injured. The total economic cost is estimated at $8 to $10 billion per year.
The underlying cause is simple. Animals don't understand roads. They never will. A deer has no evolutionary framework for interpreting headlights closing at 70 miles per hour, and a 700-pound elk doesn't know to wait for a break in traffic. They cross where their ancestral routes tell them to cross, and for most of those routes, we've laid down asphalt and called it progress.
What Works (and What Doesn't) #
The evidence on wildlife crossings is unusually clear for a conservation intervention, because you can measure it directly: count the carcasses before, count them after.
The results are consistent across multiple studies:
- Utah I-15: 98.5% decline in deer mortalities with fenced underpasses (Bissonette & Rosa, 2012)
- Trans-Canada Highway, Banff: 89% reduction in ungulate collisions across 75 crossing structures (Clevenger & Barrueto, 2014)
- Virginia I-64: 92% average reduction at fenced crossings (Cramer & Kintsch, 2020)
- Arizona SR 260: 76–83% reduction in elk-vehicle collisions with fencing (FHWA SPR-603)
But there's a critical caveat that gets lost in the headline numbers: crossings only work when paired with adequate fencing. The Montana US-93 study (Cramer & Hamlin, 2017) found that "none of the 19 wildlife crossing structures had a statistically significant effect on WVC crash rates" — because the fencing was insufficient. Without fencing, animals don't reliably use the crossings. With fencing, passage rates for elk and deer can increase from 0.12 to 0.56 crossings per approach, and collisions plummet. The two components are a package deal.
The Pew Charitable Trusts summarized it neatly in their 2026 report: "Wildlife crossings with fencing can cut large-mammal collisions by more than 80% — and up to 97% for certain species, including deer and elk."
The Economics #
Arizona's I-17 overpass is a $15.8 million project. The SR 260 corridor cost more. These aren't cheap to build.
But the math works. At $8,388 per deer collision and $30,773 per moose collision in economic costs (vehicle damage, medical care, lost work, emergency response), a single corridor preventing a few hundred crashes over its lifetime pays for itself. Arizona DOT's SR 260 study found the crossings were saving roughly $2 million per year in avoided collision costs across that corridor alone. Over a 50-year lifespan, that's a substantial return on investment — before you count the value of the animals themselves.
The Federal Highway Administration launched its Wildlife Crossings Pilot Program with $110 million in grants in its first round. Arizona's I-17 project was one of 19 nationally to receive funding, pulling in a $24 million FHWA grant alongside state and Game and Fish Department money.
Other states are following. The SR 260 Lion Springs widening project east of Payson will add more wildlife crossings along the last two-lane segment of that highway, with completion targeted for 2029.
The Thing That's Hard to Measure #
There's something these studies capture imperfectly, which is that wildlife crossings are one of the rare environmental interventions where the problem and the solution are both visible. You can see the dead deer on the shoulder. You can see the overpass with grass growing on it. The cause and effect aren't buried in a regression model — they're legible to anyone who drives the highway.
That matters, because it makes the case for replication in a way that atmospheric carbon parts-per-million doesn't. Every state has a stretch of highway where collisions cluster. Every state has a wildlife agency that knows exactly where those stretches are. The barrier isn't knowledge. It's funding and political will.
Arizona has both, and it's been quietly proving for twenty years that the problem is solvable. Not partially solvable, not solvable-in-theory, but solvable enough to cut collisions by 90% in the places where crossings are built. A million animals a day won't stop being a million overnight, but the mechanism for changing that number exists and it works.
Sources: Federal Highway Administration Wildlife-Vehicle Collision Reduction Study (Report to Congress, 2008); State Farm Annual Animal Collision Data (2024–2025); IIHS Fatality Statistics (2023); Arizona DOT SPR-603 and SPR-540 (SR 260 Wildlife Crossing Studies); Bissonette & Rosa, Wildlife Biology 18:414–423 (2012); Cramer & Kintsch, Transportation Research Record (2020); Cramer & Hamlin, Montana US-93 Evaluation (2017); Pew Charitable Trusts, "Wildlife Crossings Save Lives, Cut Costs, and Protect Animals" (2026); KNAU Earth Notes, "I-17 Wildlife Crossing" (March 2026); ADOT, "Northern AZ 2026 Highlights" (2026)