Innovating our Wildlife Underpasses: A success story of implementing data to improve state budget 

It’s no secret that CDOT is always improving the roads we’ve previously built. In the case of this story and innovation, Krohnholm and his team were focused on the I-70 Corridor. They were in the process of planning improvements when they were told by the stakeholders to make wildlife passages, and to make them just as large as reasonably possible. 

A wildlife passage is a structure that allows animals to cross roads safely. It can be a structure built above or below the road to allow for passage. In this case we’re discussing an underpass, a structure below the road. (See above)

John thought critically about the need for underpasses on I-70, upon his review, the number of wildlife vehicle collisions seemed low. Therefore, he set up a number of cameras to observe the areas next to the roadways to gather additional information on the situation.

The first thing John and his team noticed after implementing the wildlife cameras was an answer to a question, “why do we need wildlife passes here if wildlife collisions seem to be low?” His data confirmed low animal vehicle collision rates - which potentially pointed to there not being a need for such a pass.

However, upon reviewing the footage, the video showed that a large number of animals would come down to I-70, look to cross, and turn around. It wasn’t that they didn’t need to have a wildlife pass because there were no animals - but rather the wildlife had learned to avoid crossing such a loud and confusing road.

It took a few years of placing the cameras in specific locations to discover what was happening. Through this process they were able to document where and what kind of wildlife was coming down to I-70 to decide on a target species to design the underpasses with in mind.

Given this evidence of wildlife presence, John agreed wildlife passages were needed, but thought critically about how to size them correctly when the project stakeholders were pushing him to make them larger. 

When John researched how wildlife underpasses are sized, he discovered there was little evidence to show larger was better. He set out to gather data from research in 16 studies across the western US and Canada. He looked at studies which covered success rates for wildlife using underpasses to create a regional statistical model. With this data in hand, they were able to formulate an equation that could determine the size requirements of a wildlife underpass, based on mule deer specifically, one of the species largely affected by the I-70 Corridor.

Given John’s discovery, he was able to get a grant to build a robust equation and models that would help DOTs size these underpasses more appropriately. He presented this information to stakeholders so they could see the benefit of being more conservative with the sizing of a few proposed underpasses. The stakeholders agreed, and in the process of building the smaller underpasses, the state retained $1.7 Million and achieved the same (if not better) result!

On another note, John stated that he experienced plenty of positive collaboration with people because “if you want to get wildlife across the road, it is a collaborative effort with multidisciplinary teams, a variety of engineers, road ecologists, [and] wildlife biologists.”