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Coordinating, Developing, and Delivering Highway Transportation Innovations

This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-08-034
Date: August 2008

Wildlife-Vehicle Collision Reduction Study: Report To Congress

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Chapter 11. Gaps in Current Knowledge

This chapter summarizes the challenges that currently prevent a systematic, nationwide approach to WVC reduction.

Data Issues

Generally, the greatest challenge to reducing WVCs is the absence of reliable information and documentation on mitigation measures such as effectiveness, historic use, challenges, etc. This lack of data is characterized by the fact that the Technical Working Group (chapter 10), categorized 20 of the 34 mitigations as "recommended for further research." There are numerous syntheses (including this one) that summarize potential solutions to WVCs. However, the effectiveness of a number of mitigation measures is still uncertain due to lack of evaluation, inaccurate data collection, and inconsistent measures of effectiveness.

One of the challenges relating to monitoring the effectiveness of WVC mitigations is the lack of reliable standardized and spatially precise data on the location of WVCs and animal carcasses. The national databases, summarized in chapter 2, all have some shortcomings in these regards. Most importantly, location data are not included in the national databases (i.e., GES, FARS, and State Farm Insurance Claims). Most of these datasets suffer from underreporting. Inconsistently collected data make it difficult to accurately characterize WVC issues and properly address them (e.g., identifying the best location to deploy a mitigation measure to address a particular situation). Problems also arise when attempts are made to use such data to evaluate the effectiveness of various mitigation measures after they have been installed. Furthermore, data that have been collected are not always readily available or even analyzed. All of these issues pose major challenges for the current study of WVCs.

Analysis Issues

Effectiveness of mitigation measures can be evaluated relative to many different criteria. Each criterion has its own associated characteristics and methods of measurement, which can make evaluation of mitigation measures based on multiple criteria a difficult task. For example, effectiveness can relate to collision reduction (the criteria used in this study) but also to habitat connectivity. These are very different parameters, namely, safety and nature conservation, that are measured in very different ways. Development of sound methodologies to both singly and collectively consider these various criteria in evaluating mitigation measures would be useful.

Relative specifically to safety issues, some crash models exclude WVCs altogether. If AVCs are included in crash models, they tend to focus on road, traffic, and right of way characteristics only, and ecological parameters that extend away from the road are rarely included. Only a limited number of studies have looked at both groups of parameters at the same time.

Relative to specific WVC problem locations, the tendency is to identify such locations using past roadkill data. Given the investment and life span of some of the mitigation measures, it is advisable, however, to project 50–80 years into the future. The potential presence, population viability, and needs of selected wildlife species will likely change in this time period.

Needed Tools

With respect to specific mitigation technology used, basic research needs to be conducted to understand how existing mitigation measures can be made more effective. There should be a continuous drive to make these measures cheaper, smaller, more robust, and as mobile as possible to address costs, landscape aesthetics, safety concerns, operation and maintenance efforts, and a highly dynamic environment.

Modeling should be further developed and applied to assist in the optimization of the location, type, and dimensions of mitigation measures. Basic data collection is required to obtain inputs for these models. Existing long-term monitoring studies may need to be supplemented with studies that address specific questions that may not have been addressed yet. Once the recommendations based on these models have been implemented, the mitigation measures should be monitored for their effect on population viability parameters to verify that the models simulate the real world environment to an acceptable degree.

Addressing the broader picture, tools and procedures should be developed to measure the effects of roads and traffic on ecosystem processes, how these effects can be minimized, and how the disrupted processes can be restored.


To summarize, future research should focus on the following:

  • Developing and implementing guidelines and standards for collecting and reporting WVCs.

  • Developing and implementing guidelines for the evaluation of mitigation measures.

  • Evaluating the effectiveness of mitigation measures that have been recommended for further research.

  • Conducting research and development to improve existing mitigation measures.

  • Developing and applying population viability models that assist with the location, type, and dimensions of mitigation measures.

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