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75 effects of roads on wildlife movement, mortality, and habitat from project-level (< 50 km of highway) to larger district- and public safety early in the design process for transportation level or state-wide assessments on larger highway network projects. systems. The spatial accuracy of WVCs is not of critical There are a variety of GIS modeling approaches today, from importance for the relatively coarse-scale analysis of where simple to more complex models requiring high-resolution hotspots are located. To determine site-specific factors that and spatially explicit data. Most GIS modeling used for trans- contribute to WVCs, more spatially accurate data are portation planning purposes tends to be coarse scale and does required. Thus, WVCs referenced to a mile-marker system not require specially developed GIS data layers.13,65,212 Like will be sufficient for transportation agencies to identify the GIS-based data on animal movements, hotspot information location of problematic areas for motorists and wildlife. can be used to identify problematic areas and thus integrate WVC data with greater spatial accuracy are equally useful in mitigation where highway improvement capital will be determining the location of hotspots; however, they are not invested. Hotspot areas that are associated with existing essential to begin examining highwaywildlife conflict areas. below-grade crossings (e.g., drainage culverts and bridges) can The research team has outlined and described various tech- be identified by linking GIS data, allowing structural and land niques available that can help delineate WVC hotspots. Sim- planning recommendations to be made to improve perme- ple plotting of collision points is a relatively straightforward ability at unsuitable passages. means of identifying problematic areas; however, as sample In another example, WVC carcass data were used along sizes increase, the tendency for roadkilled carcasses to overlap Interstate 90 in Washington to evaluate the relationship be- (hide other points) increases. The length of highway exam- tween hotspot clusters and important landscape characteris- ined, the number of animals killed, and time period of data tics.214 Carcass density was mapped using the approach collection all influence the density of collision points. Other described earlier, classifying segments as high, moderate, or low factors such as terrain, wildlife abundance, and wildlife habitat ungulate-kill density. A classification tree analysis (using S-Plus quality adjacent to the highway will further affect the spatial 2000) was used to determine the importance of 10 landscape- distribution (random/continuous or non-random/clustered) scale variables (GIS layers comprising road and landscape fea- of WVCs on a given highway. Modeling or analytical tech- tures) in the study area. Classification tree analysis is well suited niques permit a more rigorous assessment of where WVCs are for analysis of GIS spatial data. Being a non-parametric tech- likely to occur, their intensity, and the means to begin priori- nique, it involves no assumptions of normal distribution, works tizing highway sections for mitigative actions. The nearest well with categorical data, and is robust to the relatively subjec- neighbor CrimeStat method essentially pinpoints the location tively determined sample sizes inherent with GIS raster data. of WVC hotspots, whereby the segmental analyses of WVC Further, linking these coarse-scale hotspots with environmen- densities provide a more comprehensive evaluation of mitiga- tal data (e.g., terrain, habitat suitability, zones of animal move- tion options and prioritization of mitigation schemes based ment) can provide a relatively quick and reliable project-level on cost-benefit, scheduling of transportation projects, or or district-level assessment of how to prioritize mitigation severity of motorist safety concerns. activities directed at wildlifevehicle collisions. Collection of WVC data (both reported vehicle collision and carcass collection data) by transportation departments will be increasingly beneficial, especially if the collection Conclusions procedures are more systematic. Currently, in many state In this section the research team suggests guidelines for agencies, WVC data collection is not consistent and varies hotspot application. Data on hotspots of WVCs can help from district to district. The research team is not aware of transportation managers increase motorist safety and habitat many state transportation departments that have consis- connectivity for wildlife by providing safe passage for wildlife tently used WVC hotspot data for decision making in across busy roadways. Knowledge of the geographic location transportation projects or strategic planning with future and severity of WVCs is a prerequisite for devising mitigation infrastructure plans such as STIP in mind. Systematic data schemes that can be incorporated into future infrastructure collection and protocols will allow for cost-effective use of projects such as bridge reconstruction and highway expan- the data and greater management benefits by providing sion. Hotspots in proximity to existing below-grade wildlife important baseline information for planning environmen- passages can help inform construction of structural retrofits tal mitigation in projects. Further, properly collected that can help keep wildlife off roadways and increase habitat pre-mitigation data provide a critical reference point for connectivity. ultimately assessing the performance of mitigation meas- The WVC data that transportation departments currently ures that are adopted. possess are suitable for meeting the primary objective of See Appendix E for a literature review of papers that have identifying hotspot locations at a range of geographic scales, addressed hotspot identification.