Estimates suggest that in the US alone, over 1 million vertebrates are killed on roads every day. Globally, road mortality is a major mortality source for amphibians, reptiles, birds, and mammals. For some populations — particularly of large mammals and amphibians — road mortality exceeds reproductive capacity, causing local decline.
Amphibians migrating to breeding ponds are particularly vulnerable, with road mortality capable of eliminating local populations. Owls and raptors hunting road verges face high collision risk. Large mammals including deer, moose, bears, and pumas suffer both mortality and population fragmentation from road networks.
Road mortality causes acute suffering — trauma, internal injuries, and protracted death. Animals struck but not killed may suffer for hours or days. Road collisions also cause chronic stress from traffic noise and movement for populations living near roads. Orphaned offspring after parent mortality face starvation and exposure.
Underpasses, overpasses (wildlife bridges), and culverts with appropriate habitat on approaches allow safe road crossing. Evidence from Banff National Park (Canada) shows wildlife crossing structures reduce road mortality by up to 90% for target species. Cost-benefit analysis demonstrates economic value through reduced collision insurance costs.
Seasonal volunteer bucket-and-barrier programs intercept migrating amphibians during peak migration nights. In Germany, UK, and Netherlands, these programs save millions of frogs, toads, and newts annually. Permanent tunnel systems with drift fences provide year-round protection.
Lower speed limits in wildlife movement zones, wildlife warning signs (with dynamic speed reduction when animals are detected), and road lighting design all reduce collision rates. Wildlife detection systems (thermal cameras, radar) that trigger variable message signs are increasingly being deployed on high-risk road sections.