A spatiotemporal analysis of ungulate–vehicle collision hotspots in response to road construction and realignment

MacDougall, Sandra; Bíl, Michal; Andrášik, Richard; Sedoník, Jiří; Stuart, Esther · 2024 · OpenAlex-citations

DOI: 10.5751/es-14883-290201

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Summary

This study evaluates the spatiotemporal evolution of ungulate–vehicle collision (UVC) hotspots in response to major road construction and realignment in Alberta, Canada. Motivated by the significant ecological and public safety risks posed by roads, the authors aimed to assess how infrastructure changes affect collision rates and hotspot stability. The research addresses a gap in existing literature, which often relies on short-term, geographically limited studies lacking inferential strength. By analyzing long-term data, the study seeks to determine the effectiveness of wildlife mitigation measures versus the impacts of highway expansion without such measures. The researchers conducted a comparative analysis of two distinct case studies using government police collision and carcass data from 2000 to 2021. Case Study 1 examined a highway bypass adjacent to Calgary, comparing a 4.5 km segment of a new fenced highway with wildlife underpasses against an adjacent unfenced control highway. Case Study 2 analyzed a 54.5 km segment of Highway 63 in rural Alberta, which was converted from a two-lane to a four-lane divided highway with increased speed limits but no wildlife mitigation. The study employed a novel analytical approach combining Kernel Density Estimation Plus (KDE+) with a spatiotemporal modification (STKDE+) to identify stable, emerging, or disappearing collision hotspots over time. Statistical analyses, including before-after and control-impact designs, assessed changes in UVC rates while accounting for traffic volume and wildlife population trends. The results demonstrated that the wildlife mitigation measures in Case Study 1 were highly effective, resulting in an 86% reduction in UVCs on the fenced bypass compared to the unfenced control. However, the study identified a "fence-end effect," where a new hotspot emerged at the southern edge of the fencing, and noted that high traffic volumes on the bypass created a barrier effect, shifting collision risk to weekends. In contrast, Case Study 2 showed that converting the highway to a four-lane divided road without mitigation led to a slight, though statistically insignificant, increase in UVCs. Crucially, the majority of historical UVC hotspots reemerged after construction was completed, indicating that road realignment alone did not resolve collision risks. The STKDE+ analysis successfully distinguished between stable hotspots and those responsive to infrastructure changes. The findings underscore the necessity of incorporating wildlife considerations at multiple scales throughout transportation planning. While localized mitigation like fencing and underpasses significantly reduces direct mortality, their net benefits can be compromised by surrounding road density and unmitigated adjacent routes. Conversely, highway expansions that increase lane counts and speed limits without mitigation may inadvertently sustain or reestablish collision hotspots. The study validates the utility of spatiotemporal clustering methods for monitoring collision trends, providing transportation agencies with robust tools to evaluate mitigation efficacy and prioritize resources for reducing both wildlife mortality and public safety risks.

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• roadway lighting effects