Impacts of roadside habitat restoration on animal-related vehicular collisions in New York, USA

Background/Question/Methods

In the United States, there are 264,000 km of highways. Scientists are examining if and how highway roadside right of ways (ROW) could be managed as pollinator habitats. Insect pollinators provide critical ecosystem services and have dramatically declined over the past fifty years. Yet there are concerns that efforts may attract other animals (e.g. deer) to ROWs, potentially increasing animal-related collisions. Our research objective was thus to assess if reduced mowing in highway ROWs for pollinator habitat restoration results in increased animal-related vehicular accidents. To answer this, we established a landscape-scale study across upstate New York (NY) with paired control- and reduced- mowing treatments in 29 highway segments and adjoining roadside ROWs. We have been collecting plant and pollinator abundance and diversity data since 2019. Using Accident Local Information System data available from the NY Department of Transportation (NYSDOT) and NY Department of Motor Vehicles (DMV), we collected data on both animal-related and total-vehicle collisions from 2018 through 2020 at our sites. While one earlier study examined deer-vehicle collisions along two NY highways using reduced mowing in separate years, our study is novel in its standardized/paired treatment design, size/scope, and inclusion of significantly wider range of traffic levels.

Results/Conclusions

We used linear regression models in R statistical software to assess both animal related and the total number of collisions, including site, year and treatment as fixed effects. We then used analysis of variance and post-hoc tests to compare group means. We found no significant difference in animal-related collisions across mowing treatments and years. Our preliminary analyses indicate that wildlife collisions do not increase when highway ROW mowing is reduced. Our results thus far are in line with previous studies that indicate deer may prefer areas with more frequent mowing. However, there was wide variability by location, with some sites showing significant increases in animal-related collisions and others showing decreases. These differences may be explained by ROW factors such as plant composition or highway factors such as traffic. Future analyses will incorporate additional years of collision data, ROW habitat quality assessments, and more ROW and on-road factors, including land cover and traffic. Understanding which factors are associated with improved pollinator habitat without increased collisions can help identify best practices or locations for future highway ROW restoration efforts. These data are preliminary and not yet approved by the NYSDOT.