A wildlife overpass on Washington State's busiest mountain highway has reached a milestone that conservationists once could only dream about: 10,000 successful animal crossings recorded, and a stretch of road where wildlife roadkill has effectively dropped to zero.
The Washington State Department of Transportation announced the achievement this month, confirming that the I-90 Snoqualmie Pass wildlife overcrossing has officially recorded its 10,000th successful crossing since first opening. Together with 11 wildlife undercrossings along the same stretch of highway, the corridor has now logged nearly 40,000 crossings in total since 2014.
From 39,000 Carcasses to Nearly Zero
The numbers put the achievement in stark, hopeful relief. Before the wildlife crossings were built, WSDOT removed 39,258 wildlife carcasses from state highways statewide between 2019 and 2023. In the specific stretch of I-90 where the Snoqualmie Pass overcrossing and undercrossings now stand, that number has shrunk to nearly zero.
The 10,000 figure comes from trail cameras installed throughout the corridor, which have captured every instance of an animal using the crossing. Black bears, elk, deer, mountain lions, bobcats, coyotes, and dozens of other species have all been documented making safe passage over or under the interstate — a highway that once formed a hard barrier through one of Washington State's most ecologically important wildlife corridors.
A Corridor Reconnected
The Snoqualmie Pass area sits at the intersection of the North and South Cascades, one of the most significant wildlife regions in the Pacific Northwest. The corridor links habitat for wide-ranging species like mountain lions and black bears that need large, contiguous territories to survive, feed, and find mates.
When Interstate 90 was built through the pass, it created a hard barrier that fragmented those habitats and isolated wildlife populations on either side of the road. Vehicle collisions caused thousands of animal deaths each year. The wildlife crossings were designed to reverse that fragmentation — and the data shows they are working.
Conservation Northwest, a key partner in developing and monitoring the corridor, described the overpass as having "restored the ecological integrity of the North and South Cascades by reducing wildlife vehicle collisions, reconnecting habitat, and allowing herds and solitary travelers alike to move safely through one of Washington's most important wildlife corridors."
"These crossings now serve as a national model for how transportation and conservation goals can align to restore ecological function across major highways," the organisation added.
A Model Going National
The Snoqualmie Pass success is already influencing highway planning across the United States. Research by the Pew Charitable Trusts shows that wildlife crossings can reduce large mammal collisions by up to 97 percent, and each prevented collision can save up to $110,000 in vehicle damage, emergency response, and other costs.
Washington State officials are now working to expand wildlife connectivity further along Interstate 90, with an ambitious long-term vision of bridging habitats spanning the Cascade Mountains and the Olympic Peninsula — one of the most ecologically significant wildlife corridor projects in the country.
For the 10,001st bear, elk, or mountain lion to cross Snoqualmie Pass, there will be no fanfare. Just open ground, and a path that was built for them.
