A Quiet Milestone Ten Years in the Making
Somewhere along Interstate 90 near Snoqualmie Pass in Washington State, an animal recently walked across a stretch of forested land bridge arching over one of the busiest mountain highways in the Pacific Northwest, and in doing so, became the 10,000th documented crossing recorded on that single overcrossing since monitoring began.
The Washington State Department of Transportation (WSDOT) confirmed the milestone was reached in July 2026, with the achievement being publicly reported in September. It’s a number that, on its own, might seem like a modest statistic. In context, it represents one of the more successful, quietly ongoing wildlife conservation infrastructure projects in the United States.
The Numbers Behind the Milestone
- 10,000 recorded crossings on the main I-90 overcrossing near Snoqualmie Pass, reached in July 2026
- Nearly 40,000 total wildlife crossings documented across the entire Snoqualmie Pass corridor, combining the single overcrossing and 11 separate undercrossings, since monitoring began in 2014
- Over 25,000 vehicles travel through this stretch of I-90 daily, underscoring just how much traffic volume the crossing network is designed to coexist with
What’s Actually Using These Crossings
Motion-triggered cameras positioned along the corridor have captured a remarkably wide range of species making use of the crossings, spanning everything from large mammals to amphibians that most people would never expect to see navigating highway infrastructure.
Frequently spotted large animals include:
- Deer
- Elk
- Coyotes
More specialised monitoring has also documented smaller and aquatic species using the land bridges and tunnels:
- Western toads
- Coastal giant salamanders
- American pika
Separately, bull trout, a species highly sensitive to habitat disruption, have been recorded using restored pools beneath the nearby Gold Creek Bridge, part of a broader effort to address not just terrestrial movement, but aquatic connectivity disrupted by the original highway construction.
Why This Matters Beyond Just Counting Animals
The ecological rationale behind this project goes well beyond simply preventing roadkill, though that alone would justify the investment. Interstate 90 originally cut directly through a critical wildlife migration corridor in the Cascade Mountains, effectively splitting animal populations that had historically moved freely across the landscape.
That kind of habitat fragmentation carries consequences that compound over time. Isolated populations face reduced genetic diversity as breeding pools shrink, and animals lose access to seasonal feeding grounds, mating territories, and the broader range they need to sustain healthy population levels. By reconnecting these fragmented habitats, the crossing network isn’t simply offering animals a safer path across a highway, it’s actively restoring an ecological function the original road construction disrupted decades ago.
A Measurable Safety and Financial Win
Beyond the ecological case, the crossing network has delivered concrete, measurable safety benefits, both for wildlife and for the people driving through the corridor daily.
- Wildlife-vehicle collisions in completed sections have dropped to near-zero levels, a dramatic improvement in a stretch of highway that previously saw regular animal strikes.
- Statewide, WSDOT collected 39,258 animal carcasses from Washington highways between 2019 and 2023 alone, a figure that illustrates the scale of the problem these crossings are specifically designed to address.
The financial case is just as compelling. Wildlife-vehicle collisions carry substantial average costs per incident:
| Animal | Average Cost Per Collision |
|---|---|
| Deer | ~$14,014 |
| Elk | ~$45,445 |
| Moose | ~$82,646 |
These figures account for vehicle damage, medical costs, and related expenses, and they scale up quickly across a corridor carrying over 25,000 vehicles a day. Reducing collisions to near-zero in completed sections doesn’t just protect wildlife, it represents a direct, quantifiable reduction in costs borne by drivers, insurers, and the state.
How the Crossings Are Actually Designed
Part of what makes these crossings genuinely effective, rather than simply well-intentioned, comes down to deliberate design choices aimed at making them feel like a natural extension of the surrounding landscape rather than an obvious piece of infrastructure.
- The overcrossing itself is covered with natural vegetation, trees, and terrain, engineered specifically to mimic the look and feel of the untouched landscape on either side of the highway.
- High wildlife fencing runs along the corridor, guiding animals toward the crossings rather than allowing them to wander directly onto the highway asphalt, a critical design element that funnels natural movement patterns toward safe passage points rather than leaving safe crossing to chance.
This combination, a naturalistic overcrossing paired with directional fencing, appears to be central to why animals as varied as elk and salamanders have all been documented using the network’s crossings rather than avoiding them.
What’s Next: Expansion Through the Early 2030s
The Snoqualmie Pass East project, the broader initiative behind this crossing network, is far from finished. WSDOT has outlined plans to significantly expand the corridor’s infrastructure:
- 15 additional undercrossings planned along the corridor
- 1 additional overcrossing planned, adding to the existing structure
- Target completion for this expansion phase: by 2031
- Full project completion targeted for the early 2030s
This expansion reflects a long-term, phased approach to wildlife crossing infrastructure, rather than treating the current network as a finished, standalone success. Each additional crossing point extends the corridor’s effectiveness further along I-90, closing remaining gaps where wildlife movement and vehicle traffic still intersect without a dedicated safe passage.
A Model Worth Watching Nationally and Globally
The Snoqualmie Pass wildlife crossing network offers a genuinely instructive case study in road ecology, a field increasingly recognised as essential infrastructure planning wherever highways cut through significant wildlife habitat. With nearly 40,000 documented crossings since 2014 and a clear trajectory toward continued expansion, the project demonstrates that reconnecting fragmented ecosystems and maintaining high-traffic transportation corridors aren’t mutually exclusive goals.
As WSDOT continues building out the remaining undercrossings and overcrossing through the early 2030s, the Snoqualmie Pass corridor stands as a working example of what’s possible when wildlife safety, ecological restoration, and highway infrastructure are designed together from the outset, rather than treated as competing priorities to be resolved after the fact.
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