Mean estimated traffic volume (annual average daily traffic; aadt) across the years 1986 to 2020 in Wyoming for all-vehicles (A) and truck-only (B) traffic along all roads in the road network. Hotter colors represent greater estimated traffic volume. Error, represented as the mean prediction interval across the years 1986 to 2020 in Wyoming, scaled by their respective means for all-vehicles (C) and truck-only (D) traffic. Figure adapted from Inman and others (2024).

For this study, researchers developed annual estimates of road age and vehicular traffic volume across highways, arterials, collectors, local, and gravel/graded roads within the state of Wyoming. These data can help managers ask broad questions about habitat fragmentation or identify which roads may offer an opportunity to implement temporary road closures or traffic restrictions, including limiting trucks, to increase connectivity between populations. More broadly, these metrics of road age and traffic volume help address the ‘when’ and the ‘how much’ questions of how roads may be affecting people, wildlife and landscapes we care about. These new data also have the potential to inform resource management planning where knowledge of the effects of roads and traffic volume are needed. 

After compiling these new data, researchers used them to predict rates of reported wildlife-vehicle collisions (WVCs) along a subset of roads in Wyoming. They found evidence supporting a threshold hypothesis for WVCs, wherein increases in traffic volume equate to increases in WVCs up to a threshold, above which increases in traffic volume result in declines in WVCs. These new methods will enable better-informed studies of road ecology to address how roads may affect wildlife populations and key ecosystems across Wyoming.

Publication: Inman, R.D., Robb B.S., O’Donnell M.S., Edmunds D.R., Holloran M.J., Aldridge C.L. 2024. Estimating traffic volume and road age in Wyoming to inform resource management planning: an application with wildlife-vehicle collisions. Ecological Indicators. 166(112410), https://doi.org/10.1016/j.ecolind.2024.112410 

Associated Data Release: Inman, R.D., Robb, B.S., O’Donnell, M.S., Edmunds, D.R., Holloran, M.J., and Aldridge, C.L., 2024, Wyoming road age and traffic volume estimated with machine learning and graph theory: U.S. Geological Survey data release, https://doi.org/10.5066/P137JNBY 

A) Observed relationship between number of reported vehicular wildlife collisions (WVCs) in Wyoming, USA and annual average daily traffic (aadt) of all-vehicles. The greatest number of reported WVCs were expected on roads with all-vehicle traffic volumes between 10,000 and 13,000 aadt, given all other factors. B) Traffic volume threshold hypothesis wherein the number of individuals that can successfully cross a road (dashed) decreases as traffic volume increases, but so too does road avoidance behavior (dotted). This results in a peak of observed WVCs (solid) at moderate levels of traffic volume. Figure 7 from Inman and others (2024).

This United States Geological Survey news article "Estimating traffic volume and road age in Wyoming to inform resource management planning: An application with wildlife-vehicle collisions" was originally found on https://www.usgs.gov/news

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