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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.
