Due to the ever changing climates and human travels, animals are forced to migrate in order to survive. As a result, animals are getting injured and killed in road related accidents. Underpasses have been developed in order to prevent these situations.

For example, according to the Mental Floss website, the leading cause of death for Florida panthers was fatal road hits. In 1958, 1967, and in the 1970s, the federal government and the State of Florida declared the big cat endangered, with less than 180 panthers remaining today. As of June 25, 2014, at least 12 Florida panthers had been killed by vehicles. In 2013, the death toll was 15 and in 2012, it was 18. 

The website mentions steps taken by Florida in order to prevent the animals from getting hurt. They lowered the speed limit and added warning signs about animals in the area, but these methods were proven ineffective. Other methods were developed. Underpasses and overpasses are proven to be more effective means of wildlife crossing compared to crossing regular roads.

According to the Critter Crossings website, underpasses for bears are more effective than intended. the Florida Department of Transportation developed the underpasses for black bears. They noticed that the bears were using crossings meant for panthers, and bears were getting hit on State Route 46 more than at any other stop. The bear-friendly underpass that FDOT built was 47 feet long, 24 feet wide and eight feet high.     

According to Critter Crossings, bears are not the only animal crossing through the underpasses. Twelve other species, including bobcats, gray foxes, and whitetail deer, are benefitting from the underpasses as well.