Cost effective solutions: Animal vehicle collision reduction and habitat connectivity - Final Report NDOT Research Report No. 701-18-803 TO 1 Part 4 COVER PHOTO CREDITS ➊ N. Hetherington, WTI/MSU ➊ ➋ Adobe Stock ➋ ➌ Elizabeth Fairbank, CLLC ➍ Maierpa, Wikipedia ➌ ➎ N. Hetherington, WTI/MSU ➒ ➏ N. Hetherington, WTI/MSU ➍ ➐ Matthew Bell, WTI/MSU ➎ ➏ ➐ ➑ ➑ N. Hetherington, WTI/MSU ➒ N. Hetherington, WTI/MSU SUGGESTED CITATION Ament R, Huijser M, May D. Cost effective solutions: Animal vehicle collision reduction and habitat connectivity - Final Report. Transportation Pooled Fund Study, TPF-5(358). Nevada Department of Transportation, Carson City, NV. DOI 10.15788/ndot2022.1.4 PROJECT INFORMATION View more projects and reports generated by TPF-5(358), please visit http://tpf-5-358-wvc-study.org Transportation Pooled Fund Study, TPF-5(358) Task1 Animal Vehicle Collision Reduction and Habitat Connectivity Cost Effective Solutions Final Report Edited by Marcel Huijser, Dana May, Robert Ament Robert Ament, Matthew Bell, Cheryl Brehme, Anthony Clevenger, WTI Research Team Authors John Duffield, Elizabeth Fairbank, Damon Fick, Robert Fisher, Adam Ford, Kari Gunson, Terry McGuire, Chris Neher, Kylie Paul S. Barnes, B. Ewing, P. Gould, M. Hobbs, S. Holm, USGS Contributing Authors H. Sheldon, J.A. Tracey, C. Tornaci, C. Vaughan Western Transportation Institute (WTI) College of Engineering Prepared by Montana State University Bozeman, MT Nevada Department of Transportation 1263 South Stewart Street Prepared for Carson City, NV 89712 This is report submitted by the Contractor. The opinions and conclusions expressed or implied herein are those of the Contractor. Disclaimer They are not necessarily those of the Nevada Department of Transportation or other Pooled Fund sponsors. September 30, 2022 ACKNOWLEDGMENTS ADMINISTRATING TPF PARTNER: NEVADA DEPARTMENT OF TRANSPORTATION We would like to thank the Nevada Department of Transportation (NDOT) and its many staff members for con- tributing to the administration of this pooled fund study. In particular, Ken Chambers and Nova Simpson, who were supportive of this entire enterprise and provided it leadership from start to finish. CONTRIBUTING TPF PARTNERS We are appreciative of the many agencies from both the US and Canada who joined together and worked seam- lessly on this international pooled fund study. Another inspiration was the non-profit ARC Solutions. Such broad interest in this project and its many subjects of inquiry bodes well for future implementation of its results. • Alaska DOT • Iowa DOT • Oregon DOT and Public Facilities • Michigan DOT • Parks Canada Agency • ARC Solutions, Inc. • Minnesota DOT • Washington DOT • Arizona DOT • New Mexico DOT • In cooperation with the US • California DOT Department of Transportation, • Ontario Ministry of Federal Highway Administration. Transportation TECHNICAL ADVISORY COMMITTEE We want to thank all the members of the Technical Advisory Committee (TAC) who shared their knowledge, information, time, and talent for the duration of the project. And especially for the hundreds and hundreds of pages of draft reports that were reviewed and commented upon to make them so much better: Cidney Bow- man - Oregon DOT, Steve Gent - Iowa DOT, Cathy Giesbrecht - Ontario Ministry of Transportation, Jeremy Guth – Arc Solutions, Matt Haverland - New Mexico DOT, Sandra Jacobson - ARC Solutions, Glen Kalisz - Washington DOT, Trevor Kinley - Parks Canada, Jon Knowles - Alaska Department of Transportation and Public Facilities, Me- linda Molnar – Caltrans, Amanda Novak - Michigan DOT, Larry Sarris - Ontario Ministry of Transportation, Chris Smith – MnDOT, and Justin White - AZDOT GRAPHIC AND WEB DESIGN Neil Hetherington, WTI 4 Table of Contents Acknowledgments 4 Executive Summary 6 Introduction 9 TPF Study Overview 11 Literature Review Of Mitigation Measures 14 Economics 18 Incorporating Wildlife Passive Use Values in Collision Mitigation Benefit-Cost Calculations . . . . . 18 Incorporating Deer and Turtle Total Value in Collision Mitigation Benefit-Cost Calculations . . . . . 21 Update and Expansion of the WVC Mitigation Measures and Their Cost-Benefit Model . . . . . . 23 Ecology 28 A Comparison of Elk-Vehicle Collisions Patterns with Demographic and Abundance Data in the Central Canadian Rocky Mountains . . . . . . . . . . . . . . 28 Long-Term Responses of an Ecological Community to Highway Mitigation Measures . . . . . . . 31 A before-after-control-impact study of wildlife fencing along a highway in the Canadian Rocky Mountains . . . . . . . . . . . . . . . . . . . 32 Electrified Wildlife Barriers at Fence Ends and at Access Roads . . . . . . . . . . . . . 34 Design 35 Fiber-Reinforced Polymer Wildlife Crossing Infrastructure . . . . . . . . . . . . . . 35 Research to Inform Passage Spacing for Migratory Amphibians and to Evaluate Efficacy and Designs for Elevated Road Segment (ERS) Passages . . . . . . . . . . 40 Modified Jump-Outs for White-Tailed Deer and Mule Deer . . . . . . . . . . . . . . 42 Internal Structural Cover and Ledges Facilitate the Use of Large Underpasses for Multiple Wildlife Species and Groups . . . . . . . . . . . . . . . 44 Best Practices 46 Best Practices Manual to Reduce Animal-Vehicle Collisions and Provide Habitat Connectivity for Wildlife . . . . . . . . . . . . . . . . . . . 46 Conclusions 50 References 52 List of Figures 54 List Of Tables 56 5 EXECUTIVE SUMMARY Wildlife-vehicle collisions (WVCs) are significant component of overall crashes in the US and Canada, and local populations of wildlife, both large and small, have suffered restrictions to their safe movement across roads. While there are several proven mitigation measures that signifi- cantly reduce WVCs, provide safe wildlife passage, and maintain habitat connectivity, there are many new technologies and improvements to existing effective mitigation measures that may help reduce mitigation costs. For example, established infrastructure measures such as overpass- es and underpasses with fencing can reduce large animal WVCs by 83% on average; yet these projects can be costly and don’t always consider the many crashes that involve smaller animal species, such as reptiles and amphibians. Thus, there is room for improvement, additional study, and evaluation of various existing and promising mitigation measures. This Transportation Pooled Fund Study, TPF-5(358) (TPF Study), allowed researchers to evaluate the latest information on the effectiveness of 24 different highway mitigation measures designed to decrease collisions with large wildlife, large feral and domestic animals, and small mammals, reptiles, and amphibians. It also explored the effectiveness of these same measures to enhance habitat connectivity. Through a literature review, eleven research projects, and a best practices training manual, four broad themes were addressed: economics, ecology, design, and practice. LITERATURE REVIEW The Literature Review examined 24 mitigation adequate fencing substantially reduce colli- measures. Ten of these measures were found to sions for a wide variety of species while at the achieve at least a 50% reduction in animal-vehi- same time improve habitat connectivity. The cle collisions (AVCs – wildlife and domestic/feral Literature Review also evaluated measures for animals), but only three were found to be highly small animal species. Temporary or permanent effective and proven to reduce AVCs by 80% road closures and road removal are effective or more: fencing, fencing in combination with measures that are occasionally implemented. crossing structures, and road closures. Fencing As for large mammals, fences, in combination by itself increases the barrier effect to wildlife with crossing structures, are the most common movement; therefore, fencing combined with mitigation measure deployed to protect small crossing structures, which improve connectivi- animals from road mortality as well as reduce ty, is the preferred mitigation measure in most the barrier effect of roads. Although effective, it North American landscapes. To be effective, was noted that road closures are usually a tactic crossing structures must be used in combina- only available to protected area managers to ad- tion with fences that are at least several miles dress traffic on protected area roads (e.g., parks, (5 kilometers (km)) in length to both direct wildlife refuges), particularly when seasonal animals to use the structure and to prevent animal migrations occur. them from accessing the road and traffic. In combination, wildlife crossing structures with 6 Executive Summary ECONOMICS The TPF Study conducted three different The final economic study developed a economic studies that updated and added cost-benefit analysis of WVC mitigation mea- new values to the cost-benefit analysis of WVC sures with new calculations for the direct mitigation measures and synthesized and costs of crashes with large wildlife species and developed new passive use values for species feral/domestic animals. It compared the cost of interest due to their mortality on North of preventing those AVCs with the costs of American highways. Although the implementing mitigation measures and passive use value studies did not maintaining them over their service life. cover all of North America’s com- The average cost per crash in 2020 US mon species, economic values were dollars was $19,089 for deer, $73,196 for described for deer, elk, wolves, grizzly elk, $110,397 for moose, and $82,646 for bear, turtles, and Mojave desert tortois- cattle and horses. These figures were sig- es of the southwest US. The individual pas- nificantly higher for these three species, more sive use values (2020 US dollars ($)) of these than three-fold, than in a journal article pub- species ranged from over $3,000 for an individ- lished by many of the same authors in 2009. ual turtle, $5,075 for a deer, $27,751 for an elk and more than $4 million per grizzly bear. ECOLOGY Four research projects were selected by the TPF measuring wildlife crossing structure perfor- Study’s Technical Advisory Committee to assess mance – leading to a primary recommendation the ecological consequences of AVCs and the that a variety of wildlife crossing structure effectiveness of mitigation measures. designs be considered an essential part of a well-designed mitigation system for the diverse The first project took advantage of over a de- fauna of western North America. It found that cade of existing data from the Canadian Rocky large overpasses and open span bridges con- Mountains to provide novel and rare details veyed a higher diversity of species than other on the links between road mortalities and the smaller crossing types. This project’s findings demographic structure of an adjacent elk can help inform future highway projects, population in an evaluation of elk-ve- Ecology so that they more fully consider how hicle collision (EVC) patterns. The their crossing designs help or harm results help inform the design of the passage of particular species or EVC mitigation measures that target ecological flows. the most vulnerable demographics of the elk population - subadults and The third project evaluated the ecolog- males. ical and cost effectiveness of fencing to re- duce collisions with large mammals. The study The second project had the luxury of utilizing found that wildlife exclusionary fencing created many years of data that helped to evaluate the declines in WVCs for common ungulates - elk, long-term ecological consequences of wildlife mule deer, and white-tailed deer - by up to crossings with fencing. Use of unique data sets 96%, although reductions for large carnivores allowed the project to determine species-spe- were much lower. It was estimated that in a cific and community level use of the crossings ten-year period, fencing provided a net eco- in the Banff National Park and Montana study nomic gain of more than $500,000 per kilome- areas. It also allowed researchers to explore ter, due to reduced ungulate-vehicle collisions the long-term effects of crossing design types, on the highway studied in Canada. habitat, and other factors that best explain species-specific variations in crossing use. The The last project tested five different electric study confirms the species-specific value of barriers to determine how well they keep large 7 Executive Summary wildlife from accessing highways and traffic at of the electric barrier study. The project also road access points or fence ends. Four of the found that double-wide cattle or wildlife guards five electric barriers tested created nearly a (4.6-6.6 m (15-22 ft)) are best for ungulates. complete barrier to black bears, the subject DESIGN Four of the research projects explored various structure, except for one species of mole. facets of wildlife crossing designs that sought to increase WVC reductions, habitat connectiv- The third study evaluated different “jump- ity, and cost effectiveness. outs” designed to address problems that arise when exclusionary fencing is used to separate The first project described the use of fiber wildlife from highways and traffic. Animals can reinforced polymer (FRP) materials for a large get caught on the inside of fenced road cor- wildlife overpass, focusing on the crossing struc- ridors and need to be able to safely exit. The ture and other design elements, such as fencing. experiment’s modified jump-outs nearly dou- The preliminary design of an FRP wildlife over- bled the success of mule deer in escaping the pass for a specific crossing location al- fenced road corridor; however, they had little lowed researchers to document an effect on white-tail deer and further example of a feasible, efficient, investigation into modifications is and constructible alternative to warranted. conventional steel and concrete materials. The benefits of FRP The fourth and final study of the materials were maximized through design chapter evaluated large their use in the crossing structure, underpasses used by large mammals concrete reinforcement, fencing, and and determined whether the addition light and sound barriers, which were esti- of ledges and rock piles could support un- mated to cost 5% less than a concrete structure derpass use by, and safe passage of, small an- with wood fencing and jump-outs. imals. The study found that a few species may not benefit from the ledges and rock piles due The second project was a case study that to predator-prey relationships, and others may evaluated an elevated road that allowed toads not be affected at all by such underpass treat- and other small animals to pass underneath ment. Increased users included mice, rats, and the structure safely. Referred to as an elevated rabbits (all prey species for larger carnivores), road segment (ERS), it included four new ERS as well as snakes, foxes, and coyote. Skunk designs for high volume roads. All small animal and bobcat use decreased, and there was no species that were detected in the adjacent for- change in underpass use by lizards, squirrels, est habitat were also detected under the ERS raccoons, and deer. PRACTICE The variety of research projects and the Litera- transportation planning, design, and implemen- ture Review conducted for the TPF Study con- tation and contains solutions that address a tributed to an updated body of knowledge broad range of environmental conditions, regarding the effectiveness of AVC mit- road and traffic characteristics, design igation measures and their ability to criteria, fencing elements/treatments, provide habitat connectivity. These implementation procedures, and new options, designs, and best evaluation methods. It focuses only practices provided an opportunity on those mitigation measures that to develop a Manual that focuss- were found to be effective by the es on the mitigation measures that literature review. were found to be successful as well as cost effective. It is designed for practitioners in 8 Executive Summary INTRODUCTION In 2003, Island Press published the first book on Two major subjects in that pioneering book road ecology in North America, Road Ecology: were wildlife-vehicle collisions (WVCs) and the Science and Solution. Fourteen leading ecolo- barrier effect that roads and traffic have upon gists and transportation experts from different wildlife movement and ecological connectivity. fields came together to articulate the principles Soon after the book was published, the federal and the state-of-the-science in the emerging Safe, Accountable, Flexible, Efficient Transporta- field of road ecology. They demonstrated the tion Equity Act: A Legacy for Users or the SAFE- application of those principles for those inter- TEA-LU Act (Public Law, 109-59) was passed in ested in studying, understanding, or minimiz- 2005. It included the requirement that a nation- ing the ecological effects caused by roads and al study be conducted to determine how best to vehicles. Diverse theories, concepts, and models reduce WVCs. The completed study was entitled in this “new field” were integrated to establish the Wildlife-Vehicle Collision Reduction Study: a coherent and accessible framework for trans- Report to Congress (Huijser et al. 2007) and it portation policy, planning, and projects. included the accompanying Wildlife-Vehicle Col- lision Reduction Study: Best Practices Manual (Huijser et al. 2008) to support practitioners. Figure 1: Herd of elk crossing a rural roadway in the Yellowstone River valley of Montana. (Renee Callahan, ARC Solutions). Over a decade later, this Transportation Pooled of collisions with both wildlife and domestic Fund Study, TPF-5(358) Study (TPF Study) seeks livestock - and maintaining connectivity for wild- to update the current state-of-the-science on life populations in the US and Canada. Through reducing WVCs, as well as explore effective a literature review, ten research projects, and measures to overcome the barrier effect of a best practices training manual, four broad roads and traffic on wildlife. In areas where themes were addressed: economics, ecology, there were gaps in information, the TPF Study design, and practice. The TPF Study was broad- supported research projects that more thor- er in scope than the national WVC reduction oughly explored particular highway WVC mitiga- study of 2007, in that it addressed habitat tion measures or improve habitat connectivity. connectivity while also evaluating medium- and Thus, the focus of the TPF Study was to evaluate small-bodied mammals in addition to amphibi- the importance of addressing and reducing ans and reptiles. animal-vehicle collisions (AVCs) – a combination This Final Report serves as a synthesis of the completed TPF Study and provides a summary of the literature review, each of the 11 research projects, and the best practices manual (Manual). Detailed final reports for these efforts and other supporting materials may be accessed and downloaded from the project’s website. To learn more, please visit: www.tpf-5-358-wvc-study.org 9 Introduction This Final Report provides readers with the most salient tion to support their efforts to reduce collisions with findings of each research project then directs them to large animals – wild and domestic - as well as take into each research project’s final report for more detailed consideration effective measures that provide for the information. In total, the findings of the TPF Study safety and habitat connectivity of all sizes of mammals, offer practitioners and scientists the latest informa- amphibians, and reptiles. Wildlife Vehicle Collision Reduction and Habitat Connectivity - Pooled Fund Study, TPF-5 (358), Task 1 REDUCE INCREASE IMPLEMENT Wildlife Vehicle Collisions Habitat Connectivity Cost Effective Solutions RESEARCH REPORTS Cost effective solutions: Animal-vehicle collision Cost effective solutions: Animal-vehicle collision reduction and habitat connectivity - synthesis reduction and habitat connectivity – literature review Economics Ecology Cost effective solutions: Incorporating wildlife passive use A comparison of elk-vehicle collision patterns with demographic values in collision mitigation benefit-cost calculations and abundance data in the central Canadian Rocky Mountains Cost effective solutions: Incorporating deer and turtle total Long-term responses of an ecological value in collision mitigation benefit-cost calculations community to highway mitigation measures Cost effective solutions: Cost–benefit analyses of mitigation A before-after-control-impact study of wildlife fencing measures along highways for large animal species: An along a highway i n the Canadian Rocky Mountains update and an expansion of the 2009 model Wildlife barriers: The effectiveness of electrified barriers Design to keep large mammals out of fenced road corridors Improving connectivity: Innovative fiber-reinforced polymer (FRP) structures for wildlife, bicyclists, and/or pedestrians Practices Research to inform passage spacing for migratory Cost effective solutions: Best practices manual amphibians and to evaluate efficacy and designs for elevated road segment (ERS) passages (USGS) to reduce animal-vehicle collisions and provide habitat connectivity for wildlife Wildlife barriers: Modified jump-outs for white-tailed deer and mule deer All reports, recorded presentations and other project resources can be found here: Internal structural cover and ledges facilitate the use of large underpasses for multiple wildlife species and groups (USGS) http://tpf-5-358_WVC-Study.org Figure 2: Summary of the TPF Study Final Report’s four themes and their associated projects. 10 Introduction TPF STUDY OVERVIEW The TPF Study developed, selected, and provid- and technologies. Finally, it coordinated and ed support for, priority research of new wildlife provided outreach to TPF Study partners and mitigation solutions, as well as explored and their stakeholders. The Task 1 team was led by encouraged collaboration on research and im- the Western Transportation Institute (WTI) at plementation of wildlife mitigation measures Montana State University. by state Departments of Transportation (DOTs), land management agencies, wildlife agencies, Task 2 investigated how to strategically in- and their partners in both the US and Canada. tegrate highway mitigation for wildlife and To carry out its objectives, the TPF Study was provide for habitat connectivity in trans- comprised of two primary tasks. portation planning and procedures. Task 2 was conducted by a different research team Task 1 identified cost-effective solutions that than for Task 1 and its activities are not dis- integrate highway safety and mobility with cussed in this final report. The final report wildlife conservation and habitat connectivity. for Task 2 may be found at: https://www. This was a unique opportunity to synthesize dot.nv.gov/home/showpublisheddocu- current knowledge from the US, Canada, and ment/20776/637968476353500000. internationally on effective mitigation mea- sures that reduce AVCs. It then sought to An overview of the approach used in Task 1 is improve the cost-benefit analyses of mitigation summarized below. The activities and research measures that are used to reduce AVCs and conducted are the basis for the reports synthe- field-test several improved mitigation designs sized for this Final Report. PHASE 1 PHASE 2 PHASE 3 PHASE 4 PHASE 5 $$$ $$ $$ ✓✓ ✓ ✓✓ ✓✓ ✓ Literature Review Cost-Benefit Annual Meeting/ Field Test Reporting & Tool Development Analysis Field Test Decision Best Practices Manual Communication Plan Figure 3: The five-phase process used for Task 1 of the TPF-5(358) Study. TASK 1 RESEARCH REPORTS SYNTHESIZED IN THIS FINAL REPORT As summarized in Figure 3, a five phased life crossing structures or associated design approach was used to conduct Task 1. This features (e.g., jump outs - egress structures for approach resulted in a variety of studies that animals on the traffic side of highway fencing). were generated and conducted over three It concludes with a manual on best practices years. It includes a literature review, three sep- for deploying mitigation measures that reduce arate economic studies, three ecological stud- WVCs or improve habitat connectivity. ies, and four studies on new designs for wild- 11 Overview LITERATURE REVIEW The first activity for TPF Study Task 1 was to review the existing literature and ongoing research on the effectiveness of mitigation measures aimed at: ❶ reducing collisions with ❷ improving or maintaining ❸ identifying new and large animals, including live- habitat connectivity for wild- emerging technologies that stock, and improving human life through safe crossing op- facilitate wildlife movement safety; portunities, regardless of the and reduce WVCs. size of the species (mammals, amphibians, reptiles); Information was compiled, evaluated, and reported. The review used international transporta- tion and ecological databases such as the Web of Science, Scopus, and Google Scholar, as well as proceedings from conferences and other professional reports and papers. COST BENEFIT ANALYSES OF MITIGATION MEASURES Cost-benefit analysis (CBA) for a variety of life, specifically, the economic value of wildlife WVC mitigation measures was conducted as not killed by investing in the deployment of part of the TPF Study. The CBA’s methods the mitigation measure. In the initial study were similar to those developed by Huijser (Huijser et al. 2009) the economic value for and others (2009) on their seminal work on wildlife was simply the average hunting license this subject. The authors of the 2009 paper cost for deer, elk, and moose. The TPF Study’s are also part of the TPF Study Task 1 research final report also summarizes two economic team. An important component of the CBA studies that developed or describe passive use for mitigation measures is the value of wild- values for a variety of species from whitetail Figure 4: A representation of species described with passive use values in the cost benefit analysis. Clockwise: Mojave desert tortoise (Gopherus agassizii) (Elizabeth Fairbank, CLLC), White-tailed deer (Odocoileus virginianus) (N Hetherington, WTI/ MSU), Wolf (Canus lupus) (Jim Peako, NPS), and Elk (Cervus elaphus) (N Hetherington WTI/MSU). 12 Overview deer (Odocoileus virginianus) and elk (Cervus of WVC mitigation measures is a significant elaphus) to wolves (Canus lupus) and Mojave improvement on the simplistic, nominal values desert tortoise (Gopherus agassizii). Incorpo- (costs of big game hunting fees) used as the rating these new economic values into a CBA economic basis for conserving wildlife. RESEARCH PROJECTS A Technical Advisory Committee (TAC) was Some projects required new field experiments formed with a representative from each of the to collect data and test hypotheses, while 13 contributing TPF Study partners. The TAC others took advantage of existing field data requested that the members of the Study’s re- from past or current projects being conduct- search team prepare and submit research pro- ed by research team members. Examples of posals they thought might be most useful to research proposals that emerged using existing explore. The TAC selected, via voting, projects data include a meta-analysis of wildlife species that best addressed the ecological, economic, responses to wildlife crossing structures and a technical, safety, or design needs of the miti- review of data from existing drainage culverts gation measures of greatest interest to their and the factors affecting their use by small agencies. More proposals were submitted mammals. These data were analyzed to pro- than the TPF Study could fund; therefore, what vide new and significant findings. emerged were the ten best research projects. BEST PRACTICES MANUAL The Best Practices Manual (Manual) offers procedures, and evaluation methods. It focuses practical information on the application of WVC only on those mitigation measures that were mitigation measures and habitat connectivity found to be effective by the literature review. improvements. It is designed for practitioners For each measure, the Manual will include a in transportation planning, design, and imple- general description, implementation steps, mentation. It contains solutions that address design guidelines, issues and concerns, costs, a broad range of environmental conditions, measured benefits and impacts, real-world road and traffic characteristics, design criteria, examples of the tool in use, and references and fencing elements/treatments, implementation contacts in case studies. CRASH DISTINCTION TERMS In this report, four similar but distinct terms volved. Table 1 provides an overview of these and their acronyms are used to describe crash- distinctions. es with animals depending on the species in- Table 1: Distinctions between crash terms Acronym Term Applications AVC Animal-Vehicle Collision Broadest category; refers to domestic animals and wildlife. WVC Wildlife-Vehicle Collision Refers to all wildlife species. DVC Deer-Vehicle Collision In some databases, deer can be separated out. EVC Elk-Vehicle Collision In some databases, elk can be separated out. 13 Overview LITERATURE REVIEW OF MITIGATION MEASURES Background A literature review was conducted which ly pertinent materials. The review sought to compiled, evaluated, and synthesized studies, determine the effectiveness of 24 different mit- scientific reports, journal articles, technical igation measures at reducing AVCs and wheth- papers, and other publications from the US er those same measures had any impact on and Canada and incorporated other global- maintaining or improving habitat connectivity. Figure 5: A variety of large and small wild animal species, free ranging livestock, and feral horses and donkeys are addressed in the Literature Review. Red squirrel (Sciurus vulgaris) N Hetherington, WTI/MSU), Wild horses (Equus ferus) (Dreamstime), Painted turtle (Chrysemys picta) (C M Highsmith), Coyote (Canis latrans) (N Hetherington WTI/MSU), Moose (Alces alces) (Jim Peako, NPS), Bull snake (Pituophis catenifer sayi)(J W Frank, NPS), Elk (Cervus canadensis) (N Hetherington WTI/MSU), Pika (Ochotona princeps) (J Waller, NPS), Pine marten (Martes americana) (J W Frank, NPS), Holstein cow (Bos taurus) (Adobe stock), Tiger salamander (Ambystoma tigrinum) (N Herbert, NPS), Wolf (Canis lupus) (Jim Peako, NPS), Mojave desert tortoise (Gopherus agassizii) (F Deffner, USFWS), Bobcat (Lynx rufus) (Neal Herbert, NPS). 14 Literature Review Mitigation measures were divided into three strategies: ❶ those that sought to change driver behavior (11 measures), ❷ those that sought to modify animal behavior or population size (11 measures), and ❸ measures that separated animals from traffic and the road surface (two measures). The literature review highlights the most effective approaches for reducing crashes with large wild mammal species, small wild animal species, free ranging livestock, as well as feral horses and donkeys. What Was Learned Of the 24 mitigation measures that were exam- on wildlife refuge or park roads, particularly ined in the literature review, the ten that were when seasonal animal migrations occur. Fenc- found to achieve at least a 50% reduction in ing, by itself, increases the barrier effect to AVCs are summarized in Table 2. Color coding wildlife movement; therefore, fencing com- in Table 1 indicates how well each mitigation bined with crossing structures, which improve measure performs in reducing AVCs and how connectivity, is the preferred mitigation mea- effective it is in increasing the permeability sure in most North American landscapes. To be of the road for animal movement. Negligible effective, crossing structures must be used in impact is noted in red and moderate is noted combination with fences that are at least sev- in yellow. Costs of the mitigation measures, if eral miles (5 kilometers (km)) in length (Huijser available, are reported in the final report for et al. 2016) to both direct animals to use the the TPF Study’s literature review. structure and to prevent them from accessing the road and its traffic. In combination, wildlife The literature review found only three highly crossing structures and adequate fencing sub- effective mitigation measures that are proven stantially reduce collisions for a wide variety of to reduce AVCs by 80% to 100%: fencing, fenc- species while at the same time improve habitat ing in combination with crossing structures, connectivity (Table 2). and road closures (Table 2). It was noted that road closures are usually a tactic only available to protected area managers to address traffic 15 Literature Review Table 2: Summary of the ten most effective of the 24 mitigation measures reviewed in the literature review report; they had to achieve at least a 50% reduction in AVCs with large mammals. Each measure was evaluated to determine if it reduced the barrier effect of roads to wildlife movement. Measure Effectiveness in reducing Effectiveness in reducing the collisions with large mammals barrier effect of roads and traffic Mitigation measures aimed at influencing driver behavior Seasonal wildlife warning signs 9-50% - Moderate None - Ineffective Roadside animal detection systems (RADS) 33-97% - Effective None - Ineffective Seasonal closure 100% during closure - Effective Reduces barrier effect of traffic but not the road itself (during closure only) Increase visibility: None - May increase barrier roadway lighting 57% - 68% - Moderate effect for some species. Reduce speed: traffic calming measures Unknown-59% - Moderate Unknown Mitigation measures aimed at influencing animal behavior or population size Wildlife culling 49-84% - Effective None - Ineffective Wildlife relocation 30-94% - Effective None - Ineffective Mitigation measures that attempt to separate animals from the road Wildlife barriers 80-100% (83% on average) None - Fences alone make the road into (fencing/walls/boulders) - Effective more of a barrier than without fences Underpasses and over- Varies greatly depending on passes without fencing structure design and/or location Barrier effect can be reduced Underpasses/overpasses 80-100% (83% on average) and fencing - Effective Barrier effect can be reduced 16 Literature Review At this time, the ability to reduce AVCs with vehi- Of the eleven measures that seek to change animal cle-based animal detection technology, especially in behavior or manage population size, two were found autonomous or “smart” vehicles, is poorly understood. to reduce AVC rates by 50% or greater. Both sought to That is, their ability to reduce AVC rates on actual high- manage the size of the population of the wildlife spe- ways has not been precisely studied. Early research for cies involved, either by culling or relocation (Table 2). these technologies has paid attention to their ability to Neither of these measures reduced the barrier effect of detect animals along, or on the road; it has not focused the road for wildlife. on quantifying the resultant reduction in AVC rates. While future research may prove that these new vehi- Table 2 does not report the effectiveness of the miti- cle-based technologies significantly reduce AVC rates gation measures aimed at reducing crashes with large with large mammal species on North American roads, domestic mammal species, such as cows or horses. the on-board sensors typically do not detect smaller Those were evaluated in the literature review and are species so have little potential for reducing WVCs with described in its final report; however, it was found small mammals, reptiles, and amphibians. Further- that the most effective measures were similar to those more, this technology does not reduce the barrier effective at reducing WVCs. effect of the road and traffic on wildlife. The literature review also evaluated measures for small The majority of the eleven evaluated measures that animal species. Temporary or permanent road closures seek to change driver behavior - making motorists and road removal are effective measures that are occa- more alert and slowing their vehicle speed to improve sionally implemented. As with large mammals, fences, reaction time to animals on the road - have by and in combination with crossing structures, are the most large been ineffective. Traditional warning signs, educa- common mitigation measure deployed for small animal tional campaigns, reducing posted nighttime speed lim- protection from road mortality, as well as for reducing its, and other measures, although commonly deployed, the barrier effect of roads. have scant evidence to prove that they reduce AVCs by more than 50% and have often been found to reduce AVC rates by only single digits. Only four measures in this group were found to achieve at least a 50% reduc- tion in AVC rates (Table 2): night-time lighting, roadside Link to the literature review: animal detection systems, seasonally deployed wildlife http://doi.org/10.15788/ndot2021.12 warning signs, and seasonal road closures. None of these four measures improve habitat connectivity over the long-term. Figure 6: Left: Mule deer (Odocoileus hemionus) on US95 overpass (NDOT). Right: Horses using underpass (NDOT). 17 Literature Review ECONOMICS As part of the TPF Study, three economic stud- passive use value is a fresh lens through which ies explored new valuation methods for wild- economists and transportation planners can life species that could be incorporated into the view the monetary cost of North American next generation of cost-benefit analyses (CBAs) wildlife killed on roads, beyond the price of a of WVC mitigation measures. In past studies big game hunting tag. The studies explore not the values associated with collision avoidance, only the economic valuation of big game, but related to injured or killed animals, have been many other species as well - from carnivores limited to easily identifiable, direct use animal to reptiles, some of which are listed under the values, such as the cost of a hunting license. U.S. Endangered Species Act. Another economic value that could be used is the restitution value for the loss of individuals of various species, as prescribed by govern- What is passive use value? ment. For example, forty-two states in the U.S. have restitution values for the illegal loss of big The values individuals place on the game species (Edwards, 2017). existence of a given animal species or population as well as the bequest value Another common method used to assign mon- etary value to the loss of an individual animal of knowing that future generations will is the passive use value, or the value that soci- also benefit from preserving the species. ety has given the animal. An individual animal’s Incorporating Wildlife Passive Use Values in Collision Mitigation Benefit-Cost Calculations Background This economic research project explored the ulation, as well as the knowledge that future potential use of passive-use economic wildlife generations will also benefit from the species’ values to measure the effectiveness of the preservation. This project summarized the WVC mitigation measures and, in some in- existing published literature for wildlife passive stances, improve habitat connectivity. Passive use value estimates for those species or pop- use values are also known as non-use values, ulations that may be of interest to transpor- or the monetized value society has placed on tation specialists because they are known to the existence of a given animal species or pop- suffer from animal vehicle collisions. 18 Economics Figure 7: A representation of the wildlife included in the cost benefit analysis – clockwise, Elk (Cervus elaphus) (N Hetherington WTI/ MSU), Grizzly bear cubs (Ursus arctos horribilis) (NPS), Wolf (Canis lupus) (Jim Peaco, NPS), and Mojave desert tortoise (Gopherus agassizii) (Flo Deffner, USFWS). What was Learned This study provided a summary of the current annual average values lost in the most recent literature of wildlife passive use value esti- three years (2016-2018) of the data set. By mates and per animal passive use values for forecasting the application of 25-year mitiga- selected species and populations (Table 2). tion measures (e.g., fencing) that significantly They are available for use in highway miti- reduce bear mortality, the present discount- gation measures and their CBAs throughout ed value of mitigation structures that would North America, where the species is present. prevent these deaths is between $17.5 million and $40.8 million. Thus, highway mitigation After summarizing the various passive use measures would not only prevent grizzly bear values of wildlife, the economic study provided deaths and protect motorists, but the public an example of applying the passive use value would realize a significant cost savings for the of the grizzly bear to a particular 13.7-mile (22 investment in mitigation measures. km) road segment of U.S. Highway 93 (US-93), in western Montana, that passes through the The last segment of this research project Ninepipes National Wildlife Refuge (NWR). describes a different type of economic study Currently, there are no mitigation measures for - a regional economic impact analysis (REIA). US-93 in the Ninepipes NWR. Applying the pas- REIA’s are rarely conducted for highway WVC sive use value for grizzly bears in this specific mitigation measures because they utilize a road section resulted in estimated annual costs different accounting framework, one that is associated with grizzly bear roadkill of $1.5 generally a measure of the distributive eco- million in losses, based on the 15-year average nomic impacts of a specific highway construc- bear mortality, to $3.5 million, based on the tion project on a local area or region. 19 Economics Table 3: Estimated per-animal values, by species. Original Value per Species Setting Basis of Animal 2019 Value Value Estimate per Animal (year of US Dollar value) 1989 survey of Elk Donation for winter range for Yellowstone visitors $18,325 ($1989) $36,925 Passive use 4,000 elk; contingent valuation (Duffield 1991) 1989-1990 survey of Increased value per trip Elk Yellowstone visitors (contingent valuation)/per $8,802 ($1989-90) $17,230 Viewing (Duffield 1991) elk in population 1993 national value $1,180,500 ($1993) $2,002,700 Wolves per household for - National net value National; Contingent valuation donation Passive use in a wolf recovery in for recovery of 100 wolves protected area Yellowstone $13,100 - Regional $22,300 (USFWS 1994) (ID, MT, WY) net value Regional Wolves 2005 survey of Contingent valuation donation Value outside Yellowstone visitors to compensation fund for live- $42,910 ($2005) $56,427 Yellowstone (Duffield et al. 2006) stock depredation (400 wolves) 1996 Regional and National household Contingent valuation donation Grizzly Bear survey on Grizzly for recovery of 280 grizzly in $2,578,800 ($1996) $4,133,000 Passive use reintroduction Bitterroot Ecosystem (USFWS 2000) National value per Mojave Desert Meta-analysis model for threat- household (Amuakwa $7,610 ($2015) $8,179 Tortoise (1) ened reptile/passive use value Mensah et al. 2018) Costs to protect species at Mojave Desert ESA project Ivanpah Solar facility/passive $7,282 ($2014) $7,883 Tortoise (2) mitigation costs use value An example REIA was conducted for this proj- net economic impact but surpass $8.2 million ect based on the 2010 construction of miti- in Yellowstone County. This REIA demonstrat- gation measures for the expansion of US-93 ed how larger, more complex economic areas in western Montana. It evaluated what the will receive larger economic impacts from the economic impact of constructing $4.8 million same amount of construction of highway miti- in equivalent highway mitigation measures for gation measures, compared to smaller, simpler wildlife would have upon two distinctly differ- economic areas. ent Montana counties: rural Sanders County with a small population, and Yellowstone County, which is home to Billings - the larg- est city in the state. Results of the REIA esti- Link to the final report: mated that the total economic impact of the same highway mitigation measures in Sanders http://doi.org/10.15788/ndot2019.09 County would amount to over $5.9 million in 20 Economics Incorporating Deer and Turtle Total Value in Collision Mitigation Benefit-Cost Calculations Background This pilot study developed survey methods that of previous valuation work. Within this context could be appropriate for gathering statistical- the study had several objectives: 1) develop a ly reliable data for models that estimate the reproducible survey instrument appropriate for passive use value of species commonly involved eliciting survey responses which could be used in WVCs. Currently, the economic values for the to estimate total value estimates (including pas- species used in the pilot are a missing com- sive use values) on an individual animal basis; ponent of CBAs related to the construction of 2) test a draft version of the survey to deter- exclusionary fencing and wildlife crossing struc- mine its acceptance by respondents; 3) finalize tures. While there exist many natural resource the survey and conduct a full-scale random economics publications on value estimates for household survey in a test location on selected wildlife, they almost entirely focus on either species; 4) analyze the survey data using accept- entire population value, threshold values, or ed statistical modeling methods; 5) report the values associated with significant changes in findings, including limitations of the analysis and population size. Most of these are not applica- suggestions for future research. The research ble for use in CBAs of highway mitigation mea- was conducted in the State of Minnesota, and sures that reduce WVCs. the species of interest were white-tail deer (Odocoileus virginianus) and turtles, such as This project sought to develop a method to painted turtles (Chrysemys picta) or snapping estimate economic values for animals within turtles (Chelydra serpentina). In Minnesota, species that have generally not been the focus WVCs with deer and turtles are a concern. Figure 8: Species of interest in the Minnesota study. Clockwise: Blandings turtle (Emydoidea blandingii) (Andrew Cannizzaro) and White-tail deer (Odocoileus virginianus) (N Hetherington, WTI/MSU), public information sign, (Christopher Smith, MnDOT). 21 Economics What Was Learned Based on previous general population house- = $13,277 in 2019 US dollars. For this esti- hold surveys a target response rate of 16% of mate, direct collision costs account for 63% deliverable surveys was anticipated. The actual of the loss of a deer and passive use values response rate from the Minnesota sample was account for the other 37 percent. An avoided just under 21%. This indicates that the survey collision with a turtle in Minnesota is worth an was of interest to respondents and engaged a estimated $3,070 in 2019 US dollars. greater than expected share of recipients. Based on the survey, an estimate of the total economic benefits (direct collision costs plus Link to the final report: passive use costs) of an avoided deer-vehicle http://doi.org/10.15788/ndot2021.09.1 collision in Minnesota (MN) is $8,325 + $4,952 $$$ Figure 9: Key findings from the Minnesota household survey. 22 Economics Update and Expansion of the WVC Mitigation Measures and Their Cost-Benefit Model Background Huijser and others (2009) published the first onus) combined), elk (Cervus canadensis), peer-reviewed journal article to establish moose (Alces americanus), gray wolf (Canis estimates of the average cost of collisions with lupus), grizzly bear (Ursus arctos), and free large mammals – moose, elk, and deer - in the ranging or feral domesticated species including USA and Canada. This TPF Study created an cattle, horse, and burro. The components in- opportunity to update and expand upon those cluded in the cost estimate were vehicle repair initial cost estimates. The research estimated costs, costs associated with human injuries and the cost of the average collision with a deer fatalities, and passive use costs if available. (white-tailed deer and mule deer (O. hemi- Figure 10: A sampling of animals used in the project to estimate cost of the average collision. Elk (Cervus elaphus) (Jacob W Frank, NPS), Grizzly bear (Ursus arctos horribilis) (N Hetherington, WTI/MSU), Wolf (Canis lupus) (Jacob W Frank, NPS), Wild horses (Equus ferus) (NDOT), and domestic cattle (Bos taurus) (N Hetherington WTI/MSU). 23 Economics What Was Learned The cost-benefit analyses were converted so values. The project’s estimates for the cost of that all costs were in 2020 US dollars (US$) for vehicle repairs, human injury, and human fa- each of the four categories used to estimate talities have all increased sharply since the first the average cost of collisions; vehicle repair, estimates were completed in 2007 US dollars Passive use value Average Passive human injury, human fatality, and passive use (Huijser et al. 2009) over a decade ago. Species (2020 US$)1 Notes use value Source (2020 US$) Table 4: Vehicle repair costs, average human injury costs and average human fatality costs per collision for deer, elk, and moose in 2007 and 2020. White-tailed $5,075 Outside a deer protected area $5,075 Duffield & Neher 2021 Vehicle Repair Average Human Injury Average Human Fatality In a Duffield 1991, Costs per Collision Costs per Collision Costs per Collison $37,843 protected area Duffield & Neher 2019 Elk $27,751 $17,658 In a Duffield 1991, 2007 2020 2007 2020 2007 2020 protected area Duffield & Neher 2019 Deer $2,850 $4,802 $2,702 $6,116 $1,002 $3,408 $2,052,4992 In a protected USFWS 1994, area, National Duffield & Neher 2019 Wolf $22,855 In a protected $40,342 USFWS 1994, Elk $4,550 $7,666 $5,403 $14,579 $6,683 $23,200 area, Regional Duffield & Neher 2019 $57,830 Outside a Duffield et al. 2006, protected area Duffield & Neher 2019 Moose $5,600 $9,435 $10,807 $26,811 $13,366 $46,400 Grizzly bear $4,235,770 For $4,235,770 USFWS 2000, reintroduction Duffield & Neher 2019 Data regarding the proportion of moose (0.2) used to estimate an average fatality cost of and deer (0.05) collisions that result in human $11,600,000 based on the US Department of injuries were used to estimate the cost of Transportation’s standard known as the “Value human injury in an average crash with a large of Statistical Life”. Compared to the expense of wild ungulate. Based on these two propor- repairs and human injuries, the average cost of tions, the unknown proportion of elk collisions human fatality per crash grew even more sig- that result in human injuries was assessed at nificantly, with an increase of more than 300% 0.1 percent. The human injuries were further than the amount Huijser and others (2009) categorized into three levels of severity and estimated in 2007 US dollars (Table 4). cost (in 2020 US$); possible injury ($77,200), non-incapacitating injury ($151,100) and in- The last category, passive use value, is a new capacitating injury ($554,800). In 2007, these economic factor used to estimate the cost of proportions and levels of severity resulted in an average collision with different large wildlife the following average cost of human injuries species. A summary of the passive use values to be $6,116 in collisions with deer, $14,579 of four large mammals in North America eval- with elk, and $26,811 with moose; in this new uated for the TPF Study can be found in Table evaluation, all three species collision estimates 5. Passive use values for an individual of these are significantly higher than in 2007 (Table 4). species can range from $3,000, to over $4 mil- lion US dollars. Similar to human injury, the proportion of collisions resulting in human fatality were 24 Economics Table 5: Summary of wildlife values and avoided collision costs in (2020 US dollars ($)) from both economic studies in the TPF that can be used for cost-benefit analyses (CBAs) of wildlife-vehicle collision (WVC) mitigation measures. Passive use value Average Passive Species (2020 US$)1 Notes use value Source (2020 US$) White-tailed $5,075 Outside a deer protected area $5,075 Duffield & Neher 2021 $37,843 In a Duffield 1991, protected area Duffield & Neher 2019 Elk $27,751 $17,658 In a Duffield 1991, protected area Duffield & Neher 2019 $2,052,4992 In a protected USFWS 1994, area, National Duffield & Neher 2019 Wolf $22,855 In a protected $40,342 USFWS 1994, area, Regional Duffield & Neher 2019 $57,830 Outside a Duffield et al. 2006, protected area Duffield & Neher 2019 Grizzly bear $4,235,770 For $4,235,770 USFWS 2000, reintroduction Duffield & Neher 2019 1 Conversion from 2019 to 2020 US$ based on U.S. Department of Labor (2022). 2 Not used in the calculation for the average as it relates to Yellowstone National Park. The total costs associated with the average ing with a wolf or grizzly bear were considered large wild ungulate-vehicle collision, based similar to deer, burro was considered similar on vehicle repair costs, human injuries, and to elk, and cattle and horse were considered human fatalities, is reported in Table 6. Other similar to moose. potential direct costs such as towing, accident attendance and investigation, and carcass re- In this study, the direct costs associated with moval and disposal, are not included in this ta- vehicle repair, human injuries, and human ble. The hunting value of the animal concerned fatalities, increased by over 200% compared to (a “direct use” value), was also not included. their 2007 values (Huijser et al. 2009). When However, these costs are likely to be in the the passive use values for deer, elk and moose hundreds of dollars for each category, rather are included, the direct costs of WVCs in- than in the thousands or tens of thousands, creased from 280% to over 400% compared to and are unlikely to substantially increase the 2009, depending on the species. cost estimates. The vehicle repair and occa- sional human injury and fatality costs of collid- 25 Economics Table 6: Total costs associated with large wild wildlife-vehicle collisions (in 2020 US dollars ($)). Costs per collision Cost category Deer Elk Moose Gray wolf Grizzly bear Cattle Horse Burro Direct costs Vehicle repair $4,418 $7,666 $9,435 $4,418 $4,418 $9,435 $9,435 $7,666 Human injuries $6,116 $14,579 $26,811 $6,116 $6,116 $26,811 $26,811 $14,579 Human fatalities $3,480 $23,200 $46,400 $3,480 $3,480 $46,400 $46,400 $23,200 Sub total $14,014 $45,445 $82,646 $14,014 $14,014 $82,646 $82,646 $45,445 Passive use value $5,075 $27,751 $27,751 $40,342 $4,235,770 ? ? ? Total $19,089 $73,196 $110,397 $54,356 $4,249,784 $82,646 $82,646 $45,445 The direct costs associated with vehicle re- design and construction, maintenance, and pair, human injuries, and human fatalities, their removal at the end of the 25-year service increased by a factor of 2.12 (for deer), 2.60 life for fences and 75-year service life for the (for elk) and 2.69 (for moose), compared to crossing structures. This resulted in CBAs that the 2007 values (Huijser et al. 2009). When the could identify the threshold values in either passive use values are included, these factors costs of WVCs per kilometer per year or WVC increase to 2.88 (for deer), 4.19 (for elk) and rates per kilometer per year (Table 6). 3.59 (for moose), compared to the 2007 values (Huijser et al. 2009). Results in Table 7 indicate, using the 3% dis- count rate , that if collision rates with deer are Once the average cost of collisions with differ- slightly greater than 1.5 per kilometer per year ent large mammals was calculated, a CBA was (~2.4 deer-vehicle collisions/mile/year), invest- conducted for four different types and combi- ments in underpass structures with fencing nations of mitigation measures; fence without and jump outs will provide society with a net dig barrier, fence with dig barrier, fence with economic benefit. Similarly, collision rates with jump outs and underpasses every 2 kilometers large-bodied moose can be lower than deer, (km) (1.25 miles), and fence with an over- 0.27 per km/yr (0.43 moose-vehicle collisions/ pass every 24 km, an underpasses every 2 km mile/year), to meet the economic threshold between the overpasses and jump outs. The where economic benefits to society exceed the costs of the mitigation measures included their costs of building the mitigation measures. *1 A discount rate of three percent is often recommended for public infrastructure. Conducting CBAs for public works requires a discount rate to fairly compare the costs and benefits over long time periods in order to establish, on net, whether total benefits exceed total costs. 26 Economics Table 7: Threshold values (in US dollars or crash rates) indicate when the costs of crashes involving three common ungulate species in North American are equal to the cost of the construction and maintenance of the mitigation measure. Four different types of mitigation measures are calculated. For the US dollar threshold values, a three percent discount rate*1 was used. Threshold values Fence Fence Fence (apron), Fence (apron), under- (no apron) (apron) underpass, jump-outs and overpass, jump-outs US$/km/yr*2 $7,460 $11,558 $25,388 $32,030 Deer/km/yr 0.454 0.704 1.546 1.951 Elk/km/yr 0.119 0.184 0.403 0.509 Moose/km/yr 0.079 0.122 0.267 0.337 Grizzly bear/km/yr 0.002 0.003 0.007 0.009 The final analyses for this research project sought to determine if the severity of AVCs with large mammals has increased or decreased over time. The results indicate: • Larger and safer cars have resulted in a decrease in the proportion of crashes with large mammals that result in human injuries. • Synchronously, the proportion of crashes that resulted in property damage only has increased. • There was no change in the proportion of crashes with human fatalities. In conclusion, AVCs are not only dangerous but increasingly expensive. In general, when crash rates exceed relatively low levels, the installa- tion and maintenance of mitigation measures Link to the final report: can be economically justifiable. Communities who live with moderate AVC rates could expe- http://doi.org/10.15788/ndot2022.10 rience real, significant cost savings by imple- menting effective mitigation measures. *1 The discount rate for infrastructure is used to assure that the initial investment costs are balanced with the net benefits that accrue over time during the life of the project so that they are all in present value. *2 km/yr = kilometers per year 27 Economics Ecology ECOLOGY Four research projects were selected by long-term ecological consequences of wildlife the TPF Study’s Technical Advisory Committee crossings with fencing. The third project eval- to assess the ecological consequences of AVCs uated the ecological and cost effectiveness of and the effectiveness of mitigation measures. fencing to reduce collisions with large mam- The first took advantage of over a decade of mals. The last project tested different electric existing data from the Canadian Rocky Moun- barriers to determine how well they might tains to evaluate elk-vehicle collision patterns. keep large wildlife from breaching fencing Another project also had the luxury of utilizing to access highways and traffic at road access many years of data that helped to evaluate the points or fence ends. A Comparison of Elk-Vehicle Collisions Patterns with Demographic and Abundance Data in the Central Canadian Rocky Mountains Background WVCs are a widespread phenomenon that are This study sought to provide transportation strongly influenced by the traits of the species, professionals with data analyses that inform animal population density, local terrain, road the design of effective mitigation strategies design, and traffic volumes. The mortality rate in areas where elk is a dominant species. It of different ages and sexes can either buffer describes the demographic groups (age, sex, or exacerbate how a local wildlife population body condition) of elk that are most suscepti- responds to cumulative collisions. However, ble to elk-vehicle collisions (EVCs). The team the underlying patterns of WVCs are often then evaluated how elk abundance and traffic analyzed without considering the demographic volume collectively and independently may structure of the wildlife population. influence EVCs seasonally and annually. The effect of traffic volume and population The study benefited from a wealth of EVC abundance on the rates and locations of WVCs records that were collected year-round by can help natural resource and transportation Parks Canada Agency and the Alberta Natural managers predict the long-term viability of Resources Service from 1986-2000. These EVCs wildlife populations and assess when and occurred on unmitigated sections of highway in where wildlife mitigation is most effective for the central Canadian Rocky Mountains where targeted species. In the past, transportation collisions are a concern among park managers agencies have often installed mitigation mea- and motorists, alike. sures where roadkill is the highest; this focus may ignore locations where roadkill has already depressed populations and where recovery efforts are needed to avert a population crash. 28 Ecology Figure 11: Location of study area and highways used to examine elk-vehicle collisions in the Central Canadian Rocky Mountains (TCH is Highway 1, the TransCanada Highway). What Was Learned The study provides novel and rare details on et al. 2014). These insights add to the growing the links between road mortalities and the body of evidence that demographic-specific demographic structure of an adjacent large road mitigation efforts are needed to restore mammal population. While it is well estab- animal movements at the landscape scale lished that roads can have negative impacts (Ford et al. 2017). on biodiversity, it is less clear if road mortality is selective for particular types of individuals Although all healthy elk were susceptible to within a population. By incorporating pop- collisions with vehicles, the study found that ulation structure into the analysis of EVCs, elk males and subadults were more prone to this study provides new perspectives on the EVCs and collisions occurred more frequently relative vulnerability to mortality of particular in the autumn months. Research results also groups of animals within a population. These evaluated the effects of population abundance perspectives emerged from the information on and traffic volume on EVC rates and found that local (i.e., near the road) wildlife populations in elk abundance was the primary driver. Also, Canada that are typically unavailable for most the study found that the magnitude of EVCs road mortality studies (Ramp et al. 2005; Olson was negatively correlated to traffic volumes. 29 Ecology This finding, a decline in EVC rates corresponds indicator that a population may be in decline with increasing traffic volumes, might be a and provides the evidence needed to imple- good indicator that the population of elk in ment mitigation measures before a population the study area is declining and the population crash occurs. This is meaningful to transporta- could crash without management intervention, tion and natural resource managers because in such as deploying highway mitigation mea- many cases traffic volumes and vehicle colli- sures that decrease EVC rates. sion data sets are easier to collect and compile relative to population abundance estimates. Collectively, the results help inform the de- sign of EVC mitigation measures that target the most vulnerable demographics of the elk population - subadults and males. It highlights Link to the final report: the importance in the seasonality of high EVC rates for this vulnerable demographic group, http://doi.org/10.15788/ndot2021.09.5 which is the autumn. In addition, declining EVC rates with increasing traffic volumes is a good Figure 12: Elk crossing a congested roadway. (Shutterstock) 30 Ecology Long-Term Responses of an Ecological Community to Highway Mitigation Measures Background This project took advantage of two long-term 2013. In the U.S., 39 locations received cross- programs to monitor wildlife use of cross- ing structures during the reconstruction of U.S. ing structures with exclusionary fencing. In Highway 93 that passes through the Flathead Canada, seventeen years of data collection, Reservation in western Montana. Six years of regarding the use of 37 of the wildlife cross- data were collected starting on 1 January 2010 ings constructed on the TransCanada Highway and ending on 31 December 2015. (Highway 1) in Banff National Park (NP) in Al- berta was available for analysis. Five different These two data sets allowed the project to types of crossing structure designs were evalu- determine species-specific and community ated: 1) open span bridge underpass, 2) creek level use of the crossings in the Banff National bridge underpass, 3) elliptical, metal culvert Park and Montana study areas. It also allowed underpass, 4) prefabricated concrete box un- researchers to explore the long-term effects derpass, and 5) wildlife overpass. Systematic, of crossing design types, habitat, and other continuous year-round monitoring of the wild- factors that best explain species-specific varia- life crossings began in 1996 and concluded in tions in crossing use. Figure 13: The five different types of crossing structure designs that were evaluated (Tony Clevenger, Overpass Adobe Stock). What Was Learned This study provides an unprecedented look The study confirms the species-specific value at the long-term response of a large mammal of measuring wildlife crossing structure perfor- community to highway mitigation measures. mance – leading to a primary recommendation Results highlight the value of long-term moni- that a diversity of wildlife crossing structure toring for assessing the effectiveness of miti- designs be considered an essential part of a gation measures to reduce WVCs and enhance well-designed mitigation system for the large connectivity across major roads. mammal fauna of western North America. It 31 Ecology found that overpasses and open span bridges energy (>2840 gigajoules of metabolic load) both conveyed a higher diversity of species are likely enough to alter the distribution of than other smaller crossing types. ecological processes in the Banff and Montana ecosystems. These altered ecological flows can There was no evidence that could resolve the have adverse consequences to seed dispersal, debate of whether a design incorporating a nutrient flows, trophic cascades and predation few large crossings or many small crossing which are likely altered by the location and structures performs better. It appears differ- design of wildlife crossings. In both Banff and ent species preferred different designs and Montana, the dominance of a few crossing lo- structure densities. The results indicate that a cations on ungulate passage rates likely means ‘several small’ approach is a better strategy for an inordinate density of animals, and therefore coyotes, deer, and elk. Conversely, the “fewer more intense browsing and higher amounts of large” crossings may be a better strategy for fecal nutrient depositions, in a small area. This grizzly and black bears. concentration of wildlife activity around the wildlife crossings could affect local ecological The non-linear effects of time on wildlife communities and could potentially contribute passage rates through the crossings structures to the spread of diseases. suggest that short-term monitoring efforts may fail to accurately portray the ecological bene- This project’s findings can help inform future fits of mitigation for populations and ecological highway projects, so that they more fully consid- communities. As managers rely on wildlife er how their crossing designs help or harm the crossing structures to offset the impacts of passage of particular species or ecological flows. road expansion projects and other disturbanc- es, this study will help inform designs relying on wildlife crossings. It serves as an aid in the establishment of robust, long-term monitoring Link to the final report: of the performance of mitigation measures. At the scale of ecological communities, the http://doi.org/10.15788/ndot2022.06 flows of mass (>16,000 tons of biomass) and A before-after-control-impact study of wildlife fencing along a highway in the Canadian Rocky Mountains Background Wildlife exclusion fencing has become a stan- data was available) or before-after (when no dard component of highway mitigation sys- controls are available) study designs. These tems that are designed to reduce vehicular two types of study designs limit inference and collisions with large mammals. It is often used may confuse the effectiveness of mitigation in conjunction with wildlife crossing struc- with co-occurring processes that also change tures - overpasses or underpasses - to both the rate of WVCs. To improve upon these reduce WVCs and maintain or improve habitat study types and reduce confounding factors, connectivity. Past work on the effectiveness of this project employed a replicated before-af- exclusionary fencing relied heavily on either ter-control-impact (BACI)*1 study design to control-impact (when no pre-construction assess fencing effectiveness along Highway 1, *1 Before-After-Control-Impact (BACI) experimental design is considered a statistically potent design to evaluate the effectiveness of mitigation measures to reduce the environmental impacts of a highway. Since the timing and loca- tion of the impact are known and if adequate pre-construction data are collected, the BACI design is considered an optimal choice for researchers. 32 Ecology the Trans-Canada Highway (TCH), in the Rocky pacted site (fenced highway segment). The sec- Mountains of Canada. This BACI approach ond half of the project evaluated the resultant included both time and impact factors, with a cost effectiveness of the fencing. control site (no fencing) and a comparably im- Figure 14: Common ungulates and large carnivores on, or near, roadways. Clockwise, Pronghorn (Antilocapra americana) (Shutterstock), Mule deer (Odocoileus hemionus) (iStock - N Hetherington, WTI/MSU) Elk (Cervus elaphus) (N Hetherington, WTI/MSU), Black bear (Ursus americanus) (Shutterstock) and, Mountain lion (Puma concolor) (iStock). What Was Learned The study found that the two fenced segments When considering the total societal cost of of the TCH had declines in WVCs for com- ungulate collisions, fencing provided a net eco- mon ungulates species - elk, mule deer and nomic gain within the first year of construction. white-tailed deer - by up to 96 percent. The Over a 10-year period, it was estimated that the WVC rates of large carnivores (e.g., black bear fencing would provide a net economic gain of (Ursus americanus), cougar (Puma concolor)) more than $500,000 per kilometer of impacted had a much lower response, likely due to the roadway in reduced ungulate-vehicle collisions. combination of their low sample sizes and their ability to climb over the fencing design. The study results highlight the benefits of long- term monitoring of road mitigation projects The BACI study was able to account for back- (12 or more years of WVC data) and provide ground changes in WVC rates, which were evidence of the effectiveness of fencing in re- recorded at the unfenced control sites. The ducing WVCs with large mammals, particularly background changes could then be incorpo- ungulates. It also demonstrates that fencing is rated into the raw WVC rates observed at the very cost-effective WVC mitigation measure. impacted, or fenced, highway segments, which resulted in the adjustment of the WVC rate from 96% to 90% at one of the two control sites and an increase of the WVC rate by ten Link to the final report: percent, at the other. The overall result is that the realized rate of WVC reduction effective- http://doi.org/10.15788/ndot2022.02 ness at the impact sites, those highway seg- ments with fencing, was 82 percent. 33 Ecology Electrified Wildlife Barriers at Fence Ends and at Access Roads Background As the previous study exhibited, fences, in com- collisions inside the fenced road sections. bination with wildlife crossing structures, are an extremely effective WVC mitigation measure Researchers investigated the effectiveness of and help maintain habitat connectivity. They re- various types of electrified barriers to determine liably reduce collisions with large wild mammals their efficacy at keeping large mammals, both by 80% or more when fencing extends along at carnivores and ungulates, from eluding fencing least 5 kilometers (3 miles) of road (Huijser et at access roads or at fence ends. In addition to al. 2016). Collisions that occur within the fenced field studies, this project combined data from road sections tend to be concentrated near the the field with studies reported in the literature fence ends. In addition, gaps in fences, partic- to conduct a meta-analysis of the effectiveness ularly where lower traffic-volume roads access of different types and dimensions of barriers for the highway, can result in concentrations of both ungulates and carnivores. Figure 15: An example of an electrified barrier at a fence-end. (Marcel Huijser) What Was Learned The researchers developed a series of electri- some ungulate species (species with hooves), fied barriers that could be deployed, where but double-wide cattle or wildlife guards (4.6- access roads pass through the highway fencing, 6.6 m (15-22 ft)), consisting of round bars or to keep large mammals from passing through bridge grate material situated above a pit, were the wildlife exclusionary fencing. Five types generally recommended for ungulates. These of barriers were tested on black bears: elec- types of barriers did not create an effective tric mats, three types of electrified gates, and impediment for species with paws, including electrified wires that crisscrossed the road many carnivores. However, electrified mats or adjacent to the fence gap but could be driven electrified guards did act as a barrier for both over. They found that a combination of electric ungulates and species with paws. The electri- fence and four of the five electric barriers cre- fied barriers needed to be 4.6-6.6 m (15-22 ft)) ated nearly a complete black bear barrier. wide to prevent animals from jumping across. Based on the combination of the black bear field study and published literature, the proj- ect found that single-wide cattle or wildlife Link to the final report: guards (2.1-3.0 m (7-10 ft)) were effective for http://doi.org/10.15788/ndot2022.09.30 34 Ecology DESIGN Four of the research projects explored various facets of wildlife crossings designs. The first described the use of fiber reinforced polymer materials for a large wildlife overpass, both for the crossing structure as well as for other design elements such as fencing. The second project was a case study that evaluated an elevated road that allowed toads and other small animals to pass underneath the structure safely. The third study evaluated different “jump-outs” designed to address problems that arise when deploying exclusionary fencing to separate wildlife from high- ways and traffic. The fourth and final study of the design chapter evaluated large underpasses for large mammals and determined whether the addition of ledges and rock piles could support underpass use by, and the passage of, small animals. Fiber-Reinforced Polymer Wildlife Crossing Infrastructure Background Ecologists and engineers are constantly explor- This project explored what is known about ing new methods and adapting existing tech- FRP composites, their current use for bridge niques to improve AVC mitigation measures, structures, and how they could be adapted increase motorist safety, and conserve wildlife for use in crossing structures at a real-world species. Wildlife crossing structures, combined design location. Working with the California with fences, are some of the most effective Department of Transportation (Caltrans) and mitigation measures employed around the California Department of Fish and Wildlife world. They are crucial for highway mitigation (CDFW), the selected site for this project was strategies, so there is a need for new, resource- a 12-mile section of US Highway 97 (US-97) in ful, and innovative construction techniques. Siskiyou County, California. The benefits of FRP This project explored the applications and fea- materials were maximized, through their use sibility of fiber-reinforced polymer (FRP) mate- in the design of a US-97 overpass structure, rials for an innovative wildlife overpass design. wildlife fencing, jump-outs, and light/sound The use of FRP composite materials continues barriers. Collaborating with Caltrans engineers to increase due to their high strength-to- helped identify the challenges and limitations weight characteristics, long service life, and of using FRP materials in an overpass struc- low maintenance costs. They are also highly ture by a state DOT. The final wildlife crossing customizable in shape and geometry, and in design was used to evaluate the life cycle costs the materials used for their resins and fibers. of using FRP materials in an overpass structure The future for FRP is bright as manufacturers and other related design elements compared continue to research and develop commercial to traditional materials (e.g., concrete, steel, applications that incorporate more recycled and wood). plastics and bio-based materials. What Was Learned The preliminary design of an FRP wildlife over- utilizes smaller and more mobile equipment. pass in the US-97 location serves as an example The accelerated bridge construction technique, of a feasible, constructible alternative to using combined with a reduction in maintenance and conventional steel and concrete materials. The an increased service life, could result in signifi- reduction of weight when using FRP allows for cant cost savings when using FRP compared to more efficient transport of prefabricated bridge traditional bridge materials. elements and a construction process that 35 Design Over twenty FRP manufacturers and their had materials that were feasible, or adaptable, products were reviewed to determine which for use in an FRP wildlife overpass design. Four key criteria were used to identify and ultimately select the materials that would be useful for the project: ❶ product capabilities for use in a wildlife overpass, ❷ costs in manufacturing, transportation, and construction, ❸ product aesthetics, and ❹ manufacturer interest in using their product(s) for a wildlife overpass and their support when addressing any design challenges. The Crossing Structure The US-97 design site superstructure needed to accommodate elk; the 35 m length would be to be 35 m in length, to span the highway at sufficient to cross the existing 3 lanes of traffic. Grass Lake Summit (Figure 16), and 50 m wide Figure 16: Elevation view of the US-97 wildlife overpass. Not Drawn to scale The superstructure selected for the overpass for the concrete deck. Once all the pieces of was an FRP composite tub (CT) girder pro- the 50 m-wide superstructure was assembled, duced by Advanced Infrastructure Technol- the assembly units were connected with high- ogies, LLC (AIT). The girders were corrosion strength joints. A cast-in-place concrete deck resistant and low maintenance (Figure 17) and was placed on top of the assembly units and much lighter in weight than precast concrete a curb at the edges of the crossing structure girders or steel beams. Each FRP assembly retained soil on the crossing (Figure 18). Then unit was comprised of two CT girders spaced the structure was ready for the addition of oth- at 2.3 m and connected with a thin precast er key components – light and sound barrier concrete deck. These precast assembly units fencing on both sides, soil, and landscaping. reduced the time required to crane in all the girders and reduced the need to build forms 36 Design Figure 17: A photo and the dimensions in centimeters (cm) of the FRP or composite tub girder used to form the structure for the design of the wildlife overpass structure on US-97 in Siskiyou County, California (AIT Bridges). Not drawn to scale (A). AIT composite tub girder (F). Concrete soil curb (B). Precast concrete connector (G). Perforated drainage pipe (C). FRP anchor (H). Drainage aggregate (D). Longitudinal closure joint (I). Soil (E). Cast-in-place concrete deck (J). FRP sound/light barrier Figure 18: Cross section of the wildlife overpass showing the layout of the girders, concrete deck, soil, drainage, and barriers on the bridge span in meters (m). Not drawn to scale 37 Design Other Uses of FRP Materials for Crossing Structures There are many design alternatives for provid- on both sides of the structure on US-97 (Figure ing an FRP sound and light-retaining barrier 19). After examining recycled plastic board along the edges of a wildlife overpass. Varia- densities from multiple manufacturers, it was tions include cantilevered, hollow-tube posts determined that FRP boards range from 720- that attach barrier elements or prefabricated 960 kg/m3 (45-60 pounds per cubic foot [pcf]); FRP panels directly to the concrete curb in a which is denser than traditional wood fencing. quick installation. Many of the available prod- It was predicted that the FRP boards would ucts are not labeled or marketed specifically as significantly reduce the sounds of passing ve- sound-reducing members so additional inves- hicles below when compared to a wood fence. tigation into their effectiveness should be pur- They would also eliminate the light of vehicle sued. However, the project found that there headlights and running lights from the line-of- are commercially available, recycled plastic sight of animals while they were on the over- FRP materials designed for fencing and other pass. The barrier design shown in Figure 19 non-structural applications, which are recom- used recycled plastic FRP posts with an I-beam mended for fence posts, jump-out elements, cross-section, which were connected to the and light and sound barriers. top of the soil-retaining concrete curb along the edge of the overpass. The I-shape enabled The study recommended that a simple, recy- FRP boards to quickly slide into the horizontal cled plastic FRP light and noise barrier design position, held in place by the I-shaped flanges. resembling a traditional wood fence be used Figure 19: Rendering of a recycled-plastic sound and light barrier installed on top of the FRP overpass on US-97. 38 Design Another readily available product using re- straight sections of fencing or placed in a con- cycled plastics is FRP lumber. For the US 97 crete base with bracing for additional support site, recycled plastic FRP posts and boards at corners, slope changes, and turns. Recycled were recommended for the wildlife fencing plastic boards are recommended for fencing elements (e.g., fence posts, gates, jump-outs). elements because they will last longer than Wildlife fencing made with FRP materials uses traditional materials, remove landfill waste, the same construction techniques as conven- and can be recycled if sections of the fence tional steel and wood wire-mesh fences. Fence need to be replaced. posts can either be driven into the ground for Life Cycle Costs of FRP The project evaluated the use of FRP girders in For the US-97 wildlife overpass design, using other research and found that the initial cost the FRP tub girders was estimated to cost 11% of FRP girder bridges may be higher than con- more than a prestressed concrete bridge, but crete and steel types, but their life cycle costs 30% less than the steel equivalent. Further- are lower due to their durability and assumed more, using recycled plastic FRP for wildlife reduction in maintenance costs. In other proj- fencing, jump-outs, and road access points ects, such as a FRP composite tub girder bridge along US-97 is estimated to cost 38% less than in Florida, the bridge was estimated to cost wood and 28% less than steel over 100 years. 40% less than a prestressed concrete girder An evaluation of the entire mitigation area reinforced with carbon-steel and 14% less than shows that the use of FRP materials is the most the same prestressed concrete girder with competitive option. Wildlife fencing elements stainless-steel reinforcement. These estimates made with wood combined with an over- were calculated using a 100-year service life. pass made from concrete is estimated to cost In Sweden, a glass FRP wildlife overpass was $10,453,856 (in 2019 US dollars [US$]) over estimated to cost 49% less than the concrete 100 years. Wildlife infrastructure built with equivalent, and 21% less than a carbon FRP recycled plastic FRP and a FRP tub girder over- design over a 120-year service life. A glass- pass structure is estimated to cost $9,961,309 FRP wildlife overpass had maintenance costs (2019 US$), 5% less than wood and concrete. estimated to be 50 to 80% less than steel and The initial cost of constructing a FRP wildlife concrete equivalents. crossing may be more expensive than using concrete, steel, and wood, but FRP materials last longer and have lower maintenance costs. Summary The preliminary design of an FRP wildlife over- ed by a state DOT with minimal departure from pass for a specific crossing location allowed traditional materials and construction tech- researchers to document an example of a niques while still saving money over the life of feasible, efficient, and constructible alternative the structure. to conventional steel and concrete materials. The benefits of FRP materials were maximized, through their use in the US-97 superstructure, concrete reinforcement, fencing, and light and Link to the final report: sound barriers. The final report documents an http://doi.org/10.15788/ndot2022.09 FRP wildlife overpass that could be implement- 39 Design Research to Inform Passage Spacing for Migratory Amphibians and to Evaluate Efficacy and Designs for Elevated Road Segment (ERS) Passages Background Amphibians are known to be particularly sus- dard mitigation solution. However, there is re- ceptible to the negative effects of roads; many cent evidence to suggest that tunnel mitigation move slowly, do not avoid roads and are not systems compress the migratory movements of avoided by drivers. Narrow tunnels that are un- species that typically disperse over large areas, derpasses that are less than 1m (39 inches) per and unintentionally cause population decline. side, connected with barrier fencing, are a stan- This project sought to determine; ❶ the distances that the Yosemite toad (Anaxyrus canorus) will move along barrier fencing before they “give up” and move back into the habitat and ❷ the efficacy of a novel road crossing prototype for toads and other small wildlife species. The Yosemite toad is an endangered species and an endemic toad found only in California. Figure 20: Male (left) and female (right) Yosemite toad (Anaxyrus canorus) (Maierpa, Wikipedia). The prototype crossing structure was an ele- tions that could be implemented on high traffic vated road segment (ERS) on a US Forest Ser- volume roads and highways. The results helped vice Road that was raised 8 in (20.3 cm) above determine the minimum distances required the ground level. It was nearly 100 feet (30.5 between toad crossings to support popula- m) wide and allowed both light and rain to tion-level movements across roads. It also pass through (Figure 21). It could also be made developed concept plans for a small animal any length. The project included an assessment crossing structure design that more effective- by transportation engineers, in collaboration ly provides habitat connectivity and offers an with Caltrans, that provided insight, guidance, alternative to below-grade tunnels for sensitive and concept designs for similar crossing solu- amphibians, reptiles, and small mammals. What Was Learned On average, Yosemite toads moved 46 m (151 the elevated road segment. Many individual ft) along barrier fencing before “giving up” and toads moved back and forth along the fencing their probability of reaching a crossing de- and approximately 90% of toads were estimated creased rapidly with increased distance from to move 20 m (26 ft) or more along the fence, 40 Design Figure 21: Left to right, top to bottom, Yosemite toad (Anaxyrus canorus) at a monolithic 5 mm diameter polyethylene fence. Vehicles driving on the Elevated Road Segment (ERS), 3D rendering of an ERS concept design (C Brehme, USGS et al). with an average distance of 46 m (151 ft). These sufficient to enable reproductive and genetic results suggest that crossing structures spaced connectivity. within 20 m of one another along Yosemite toad migratory pathways are likely to provide con- Lastly, the project demonstrated that the ERS nectivity for up to 90% of the population. has great potential to provide increased con- nectivity for a wide range of other amphibian, The direction Yosemite toads turned when reptile, and small mammal species while great- reaching the barrier fencing had a large in- ly reducing road mortality. All small animal fluence on whether they reached a crossing. species that were detected in the forest hab- Toads that reached the barrier fencing and itat were also detected under the ERS struc- then travelled in the wrong direction (away ture, except for one species of mole. from the passage) were significantly less likely to reach the passage than toads that made the As part of the project, an engineering firm correct initial direction choice. produced four ERS concept designs that re- ceived engineering evaluations for their use in The average distances moved by Yosemite similar crossing structures on primary roads toads were significantly greater along solid and highways. This project provided very use- fencing than along mesh fencing (1.8 times ful information for the future development of greater). These differences were particularly ERS crossings on high traffic roads that impact marked for adult toads, whose movement small animal, reptile, and amphibian popula- distances averaged 2.7 times greater along the tions in other locales. solid fence. This suggests solid fencing may be more effective than mesh if fencing is used for the purpose of leading migrating amphibians Link to the final report: and other small animal species to a passage. The authors noted that for non-migratory https://bit.ly/Tpf-5-358_ species, more widely spaced crossings may be WVC_USGS_ERS_Passages 41 Design Modified Jump-Outs for White-Tailed Deer and Mule Deer Background Although widely deployed throughout North beds*1 on top and bottom of the jump-outs America, there is no standard design guidance (Huijser et al. 2016). As part of this long-term for effective “jump-outs” or “escape ramps” by study, more detailed monitoring with wildlife which animals caught on the inside of fenced cameras evaluated ten of the jump-outs over road corridors can safely exit. There have three years. It determined that only 6.88% of been designs with various jump-out features, the white-tailed deer and 32.35% of the mule such as a range of wall heights or “faces” of deer detected on the top of the jump-outs the jump-out (Figure 22), the grade of the jumped down to the safe side of the fence (Hui- approach slopes (Figure 23), and whether to jser et al. 2016). None of the deer that passed place a perpendicular fence to guide animals by on the outside of exclusionary fencing were to the opening (Figure 23). These heights, captured jumping up into the fenced road corri- slopes, and related design features can vary on dor via the jump-outs (Huijser et al. 2016). the same highway mitigation project. As part of the new study, most of the ten jump- This project investigated the effectiveness of outs monitored with cameras were lowered to modifying existing jump-outs on US Highway 1.5 m (5 ft) and provided with a top bar that 93 on the Flathead Reservation in western varied in height and setback (i.e., distance to Montana. Existing jump-outs varied in height the face of the jump-out). The researchers in- between 1.75 and 2.04 m (5.7-6.7 ft). vestigated the potential increase in desired use (i.e., jumping down) and undesired use (i.e., Between 2008 and 2015, the 52 jump-outs in jumping up) for white-tailed deer and mule the study area were monitored using tracking deer with different configurations of the bar. Figure 22: A view of a jump-out from outside the exclusionary fencing. The concrete block wall is designed to be high enough to dissuade animals from entering the roadway corridor, yet low enough for animals inside to jump to the outside of the fenced roadway corridor (Marcel Huijser). *1 Tracking beds are soft sand areas that are monitored on a regular basis to count what species used them and what direction the animal was headed (jumping up and inside the fencing toward the highway or jumping down and out of the fencing and away from the road). After each monitoring event, they are raked smooth to capture future animal use. 42 Design Figure 23: A view of a jump-out on the highway side of the fencing with a perpendicular fence that is designed to direct animals following the exclusionary fence to use the jump out (Marcel Huijser). What Was Learned The modified jump-outs (see Figure 24 for an example) nearly doubled the effectiveness in allowing mule deer to escape the fenced road corridor. However, there was no improvement for white-tailed deer and further investigation into modifications of the bar, with a lower Link to final report height and greater setback, are warranted. It may be that a jump-out height of 1.5 m (5 ft) is http://doi.org/10.15788/ndot2018.2022 too high for white-tailed deer, regardless of the presence, height, and setback of a bar. Figure 24: A jump-out that is modified with a 2 in (5 cm) by 2 in (5 cm) bar for the design experiment (Marcel Huijser). 43 Design Internal Structural Cover and Ledges Facilitate the Use of Large Underpasses for Multiple Wildlife Species and Groups Background To date, most studies that evaluate the effec- A US Geographic Survey (USGS) team set about tiveness of large underpasses designed to offer to complete a two-year BACI field study on animals safe passage across highways have eight large upland wildlife underpasses in San focused on large animal movements, primar- Diego County, California. The objectives of this ily the carnivores and ungulates which were study were to determine; the focus of the structural designs. The many other, often smaller, and less mobile species ❶ if small vertebrate species are using that might make use of the same overpass or these underpasses, underpass structures are often not evaluated. ❷ if ledges and the addition of structural ele- Often, design guidance recommends the incor- ments (concrete block piles 5 m (16.4 ft) apart poration of structural elements that provide along one side of a structure) within under- more complex underpass habitat for these passes facilitate small animal movement, and smaller or less mobile species, although this is often unsupported by evidence. Consequently, ❸ if the addition of these structural elements more studies are needed to determine the ef- (piles of blocks) might adversely affect the use fectiveness of the design features that support rates of medium- and large-bodied mammals. the needs of these other species. Figure 25: Clockwise: concrete underpass, internal structure/cover treatments, Granite spiny lizard (Sceloporus orcutti), California king snake (Lampropeltis californiae), and Rat (Rattus), (Photos: Cheryl Brehme and Robert Fisher, USGS). 44 Design The USGS team selected a BACI design to Animal use was monitored by deploying mo- investigate whether adding structures to the tion detection cameras. eight large underpasses improved small ver- tebrate use. A pre-treatment sampling period The results of this study will help inform the was conducted to establish baseline conditions design of future large underpasses so that they and relative activity of species and species can effectively support large mammals as well groups within and outside the underpasses. as a variety of other smaller species from near- Then the treatment was applied to half of the by wildlife communities. underpasses and a second sampling was taken. What Was Learned There were a variety of small wildlife responses that the cinder block piles did not create a to the addition of cinder block piles along one barrier effect for the target species for which side of each of the treated underpasses. The the underpasses were designed. The applica- authors surmised that the increase in preda- tion of piles of cinder blocks on one side of the tors, such as coyote (Canis latrans), may have treated underpasses provided strong evidence been due to the increase in prey using the that providing cover increases use by a variety cinder block piles as cover, and that the decline of species, particularly prey species that may in bobcats (Lynx rufus) and skunks (Mephitis typically avoid large open underpasses. The mephitis) may have been due to their known study found that a few species may not benefit avoidance of coyote, whose use of the under- due to predator-prey relationships, and others passes increased. Deer (Odocoileus spp.) use may not be affected at all by such treatment. did not change, which appears to demonstrate INCREASED USE Mice, rats, and rabbits (all prey species for larger carnivores) snakes, foxes, coyote NO CHANGE IN USE Lizards, squirrels, raccoon, deer DECREASED USE Skunk, bobcat Figure 26: Summary of changes in underpass use by various species after the installation of internal structure/cover treatments. The monitoring and evaluation of the ledges species and as a safe haven by mice. It was in the large open underpasses, to which there recommended, based on the amount of use were no on or off ramps, revealed extensive by the various small species, that ledges with use by mice. The mice would use a ledge ten ramps be added to large overpass structures as times more than the area outside the under- standard practice in future designs. pass and five times more than the floor of the underpass. However, the ledges were used much less frequently by rats and lizards. The Link to the final report: authors surmised that the ledges were used as both a hunting perch by several of the small https://bit.ly/Tpf-5-358_WVC_USGS_ Underpass_Internal_Structural_Cover 45 Design BEST PRACTICES The variety of research projects and tices, the selection of countermeasures, design the literature review conducted for the criteria, fence elements such as jump-outs, ve- TPF Study has contributed to an updated body hicle and pedestrian access, product guidance, of knowledge regarding the effectiveness of and species-specific designs have all been WVC mitigation measures and their ability to incorporated into the Manual. The addition provide for habitat connectivity. The TPF Study of new technologies for animal identification also offers new options, designs, and best prac- – drive warning systems, maintenance con- tices. This provided an opportunity to develop cerns, and cost-benefit analyses can all provide a Manual that focusses on those mitigation guidance for the implementation of mitigation measures that were found to be successful as measures across North America’s broad range well as cost effective. Best management prac- of species, environments, and habitats. Best Practices Manual to Reduce Animal-Vehicle Collisions and Provide Habitat Connectivity for Wildlife Manual Structure The Best Practices Manual (Manual) provides practical information for the implementation of mitigation measures designed to: 1i mprove human safety through improve or maintain habitat reduced collisions with large connectivity for terrestrial animals, including large wild mammal wildlife species and selected species, select free-roaming large feral feral species through safe species, and select free-roaming large crossing opportunities. livestock species; and, 2 The Manual focuses on three main species groups: section A section B section C relates to large addresses large livestock focuses on small wild mammals, and feral animals, wildlife species. The recommended mitigation measures for each of the three species groups are then described. The Manual does not include all possible traffic will not be forcibly reduced or halted. measures that can or may reduce AVCs and In addition, culling, relocating and anti-fertility maintain or improve habitat connectivity for treatments were not considered acceptable wildlife. It is presumed that roads will not be mitigation measures for livestock, but could be permanently or temporarily closed, and that considered for large feral mammals. 46 Best Practices Summary of Recommended Measures Large Wild Mammals The term Large Wild Mammals Barriers (fences) in The Manual highlights consider- refers to North American wild combination with ations for planning and design mammal species that have a crossing structures are that include fence end treatments, body size and weight larger access roads, and jump-outs or than a coyote (Canis latrans). recommended as the escape ramps. Guidance is provided most effective of the for implementation, construction, mitigation measures. operations, and maintenance. Figure 27: Typical large ungulate fence in North America, 8 ft tall, wooden posts and mesh-wire fence material, US Hwy 93 North, Montana, USA. Note that there is a dig barrier attached to the main fence material (e.g. for canids) (Marcel Huijser). Large Domesticated Species Large domesticated species are divided into though this is often not the case (Creech et al. free roaming livestock and feral (escaped from 2019). In locations where livestock- and wild- domestication) horses and burros (donkeys). life-vehicle collisions occur in the same loca- In many places in the western U.S. there are tions, the mitigation measures for large wildlife vast areas of open range (no fences) on both species can effectively reduce collisions and public and private lands. In open range areas, provide connectivity for both wild and domes- livestock are not required to be contained and tic species. are free to move across the landscape, includ- ing roads. In some cases, it is appropriate to Despite only representing a small proportion simply install right-of-way fencing to keep live- of all AVCs nationwide, collisions with livestock stock from accessing the road corridor, while can be locally abundant. Some states experi- in other cases livestock may need to be able ence higher rates of collisions with livestock to be able to move freely across the road to than others; 15% and 16% of the reported access resources such as forage and water. In AVCs in California and Utah, respectively these cases, fencing must connect to suitable (Perrin & Disegni 2003; Huijser et al. 2008) crossing structures. When designing mitigation and collisions with livestock can account for a measures for livestock, it is imperative to con- significant portion of all AVCs and their asso- sider the wildlife in the area. Measures aimed ciated human safety risks in some rural areas at reducing collisions with livestock should not (Creech et al. 2019). Rural roads with high come at the expense of wildlife. In some cases, design speeds, high speed limits, and no artifi- concentrations of livestock-vehicle collisions cial lighting present the highest risk for human may coincide with concentrations of WVCs, fatalities associated with AVCs. 47 Best Practices Collisions with livestock such as cattle and lations have been steadily increasing on west- horses are much more dangerous on a per-col- ern U.S. public rangelands (Scasta et al. 2018). lision basis than collisions with wildlife, as the Collisions with feral large mammals can be most abundant wild large mammal species in locally common, can be a substantial concern crash and carcass databases are much smaller for human safety, and may require measures and lighter (e.g., deer (Odocoileus spp.) (Cra- to reduce these collisions (Creech et al. 2019). mer & McGinty 2018; Creech et al. 2019). In The literature on research and best practice Montana, livestock collisions are three times as management for feral large mammals is limit- likely to result in a human fatality than colli- ed (Boyce et al. 2021), particularly relating to sions with wild species, and 1.5 times more interactions with roads (Gagnon et al. 2022). likely to result in an incapacitating human injury (Creech et al. 2019). Similarly, studies in The most effective collision mitigation mea- Utah, Nevada, and Texas have also found that sures for feral horses and burros detailed in livestock collisions are more likely to result in the Manual include culling, relocation, anti-fer- human injury or death than the average colli- tility treatment, roadside animal detection sion with a wild species systems, virtual fencing, physical fences, fences in combination with crossing structures, access AVC mitigation measures for free roaming points, and fence ends. livestock include roadside animal detection – driver warning systems, physical barriers (fenc- The most effective collision mitigation mea- ing) and fences in combination with crossing sures for feral horses and burros detailed in structures. the Manual include culling, relocation, anti-fer- tility treatment, roadside animal detection Feral horse-vehicle and burro-vehicle collisions systems, virtual fencing, physical fences, fences are a considerable and increasing problem in in combination with crossing structures, access certain areas (Cramer & McGinty 2018; Gag- points, and fence ends. non et al. 2022) as feral horse and burro popu- Figure 28: Wildlife friendly livestock fence with smooth top and bottom wires, Montana, USA (Marcel Huijser). 48 Best Practices Small Wildlife Species Small wildlife species include small wild mam- robust and effective way to reduce direct road mal species (no minimum size for the species, mortality for small animal species, while also but maximum size approximates a coyote), allowing the animals to cross safely to the oth- wild reptile species, and wild amphibian spe- er side of a road. While crossing structures as a cies in North America that are fully or predom- stand-alone measure can provide connectivity, inantly terrestrial. This excludes flying species they need to be combined with fences or other and arboreal species, as well as invertebrates. barriers to reduce direct road mortality. If there are multiple target species with different As a rule, barriers for small wild animal species habitat requirements, multiple structures that should be combined with crossing structures accommodate different species requirements and the combination should be regarded as a may be required (Table 8). Alternatively, larger package. For high volume roads and roads that structures that accommodate multiple habitat cannot be closed or removed, the combination types and environmental conditions can help of barriers and crossing structures is the most address this issue. Table 8: Suitability of different types of mitigation measures for selected small and medium sized mammal species. Wildlife Open span Large Medium Small- overpass bridge mammal mammal medium underpass underpass mammal pipes Badger      Beaver    ? ? Fisher      Grey fox      Opossum      Porcupine    ?  Raccoon     ? Red fox      Ringtail      Skunks     ? Squirrels      Wolverine   ? ?  Key:  Suitable  Likely suitable  Not suitable ? Unknown/unsure if suitable The Manual provides guidance for planning and design, barrier considerations, and en- hancing existing structures for small wildlife. Implementation, construction, operation, and maintenance practices are placed in the fol- lowing three categories: Link to the Manual: ❶ Fences and Other Barriers, http://doi.org/10.15788/ndot2022.2 ❷ Wildlife Crossing Structures, and ❸ Jump-outs or Escape Ramps. 49 Best Practices CONCLUSIONS This Transportation Pooled Fund Study, TPF-5(358), was a cooperative international effort of nine state departments of transportation, a Canadian provincial ministry of transportation, Parks Canada Agency, a non-governmental organization, ARC Solutions, all acting in concert with the US Department of Transportation’s Federal Highway Administration. Combining over $1 million in resources allowed Task 1 of the TPF Study to conduct a literature review, three economic studies, and eight scientific research projects. It also produced a Best Practices Manual and a final report. LITERATURE REVIEW Researchers conducted a literature review to The ten mitigation measures that were found evaluate the latest information on the effec- to achieve at least a 50% reduction in WVCs tiveness of 24 different highway mitigation were: night-time lighting, roadside animal measures designed to decrease collisions with detection systems, seasonally deployed wildlife large wildlife, large domestic animals, and warning signs, seasonal road closures, wildlife small mammals, reptiles, and amphibians. culling, wildlife relocation, fencing (although it It explored the effectiveness of these same reduces habitat connectivity), wildlife crossings measures to maintain or enhance habitat con- alone (highly variable), underpasses/overpass- nectivity. The results of the literature review es with fencing. The last measure was found to indicate only nine measures achieved at least a be highly effective at both reducing WVCs and 50% reduction in WVCs and of these, only two the barrier effect of roads and traffic. – overpasses and/or underpasses, or overpass- es and/or underpasses with fencing – main- tained or increased habitat connectivity. ECONOMICS The TPF Study conducted three different The final economic study developed a cost economic studies, they updated and added benefit analysis of WVC mitigation measures new values to the cost-benefit analyses of with new calculations for the direct costs of WVC mitigation measures and synthesized and crashes with large wildlife species and domes- developed new passive use values for species tic animals. It compared the cost of preventing of interest due to their mortality on North those AVCs with the costs of implementing mit- American highways. Although the passive use igation measures and maintaining them over value studies did not cover all of North Amer- their service life. The average cost per crash in ica’s common species, economic values were 2020 US dollars ($) was for deer ($19,089), elk described for deer, elk, wolves, grizzly bear, ($73,196), moose ($110,397), cattle and horses turtles, and Mojave desert tortoises of the ($82,646). These figures were significantly southwest US. Individual passive use values higher, more than three-fold, than in a journal (US 2020 dollars) of these species ranged from article published by many of the same authors over three thousand US dollars for an individ- in 2009. ual turtle, $5,075 for a deer, $27,751 for an elk and more than $4 million per grizzly bear. 50 Conclusions ECOLOGY A group of the research projects evaluated var- white-tailed deer - by up to 96%, although re- ious facets of the ecological consequences of ductions for large carnivores were much lower. highway mitigation measures designed to re- It was estimated that in a ten-year period, the duce WVCs. One study provided novel and rare fencing would provide a net economic gain details on the links between road mortalities of more than $500,000 per kilometer, due to and the demographic structure of an adjacent reduced ungulate-vehicle collisions. The last elk population. Another used nearly two de- ecological study experimented with five dif- cades of data to evaluate the species-specific ferent electrified barriers that can be used at use of wildlife crossings and explore the long- the intersections of low volume access roads term effects of crossing design types, adjacent and the highway or at fence ends. Four of the habitat, and other factors that best explain five electric barriers tested created nearly a species variation in crossing use. complete barrier to black bears, the subject of the electrified barrier study. The project A third research project found that wildlife also found that two cattle or wildlife guards exclusionary fencing created declines in WVCs set side by side (4.6-6.6 m (15-22 ft) wide) are for common ungulates - elk, mule deer, and best for ungulates. DESIGN The final four research projects explored new for one species of mole. designs for WVC mitigation measures and improved habitat connectivity. The first de- The third experiment designed jump-outs veloped a design that used Fiber Reinforced which allow animals caught on the inside of Polymer (FRP) materials to replace traditional fenced road corridors to safely exit. The experi- steel, concrete, and wood in a wildlife over- ment’s modified jump-outs nearly doubled the pass crossing. A wildlife crossing employing a effectiveness in allowing mule deer to escape FRP tub girder overpass structure and recycled the fenced road corridor; but, had little effect plastic FRP posts and boards for fencing, sound on white-tail deer. The last experiment added barriers, gates and jump-outs was estimated to piles of cinder blocks along one side of large, cost $9,961,309 (2019 US$) for the US 97 site, open underpasses designed for deer to facil- 5% less than a concrete structure with wood itate the movement of smaller species. Mice, fencing and jump-outs. rats, and rabbits (all prey species for larger carnivores) as well as snakes, foxes, and coyote The next design project evaluated the efficacy all increased their use in the underpasses test- and success of a novel road crossing proto- ed, while creating no impediment for deer use. type for toads and other small wildlife species, The underpasses also had low ledges along the referred to as an elevated road segment (ERS), sides of the structures. It was determined that and included four new ERS designs for high vol- mice used a ledge five times more often than ume roads. All small animal species that were the underpass floor and ten times more often detected in the adjacent forest habitat were than outside the underpass, indicating ledges also detected under the ERS structure, except are considered a safe haven for these species. MANUAL The TPF Study also produced a Manual of Best effective mitigation measures to reduce WVCs Practices that offers the best available informa- and those that improve habitat connectivity. tion to practitioners that seek to employ the 51 Conclusions REFERENCES • Amuakwa-Mensah F, R Bärenbold, and O Riemer. 2018. Deriving a Benefit Transfer Function for Threatened and Endangered Species in Interaction with Their Level of Charisma. Environments, 5:31. • Bell M, Fick D, Ament R, Lister N-M. 2020. The use of fiber-reinforced polymers in wildlife crossing infrastructure. Sustainability, MDPI, Open Access Journal, vol. 12(4), pages 1-15, February. • Boyce PN, Hennig JD, Brook RK, McLoughlin PD. 2021.Causes and consequences of lags in basic and applied research into feral wildlife ecology: the case for feral horses. Basic and Applied Ecology, 53, 154-163. • Brehme, C., Barnes, S., Ewing, B., Vaughan, C., Hobbs, M., Tornaci C., Gould, P, Holm S. Sheldon, R. Fisher. 2022. 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Missoula, MT. 53 References LIST OF FIGURES Figure 1: Herd of elk crossing a rural roadway in the Yellowstone River valley of Montana. (Renee Callahan, ARC Solutions). . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 2: Summary of the TPF Study Final Report’s four themes and their associated projects. . . . . . . . 10 Figure 3: The five-phase process used for Task 1 of the TPF-5(358) Study. . . . . . . . . . . . . . 11 Figure 4: A representation of species described with passive use values in the cost benefit analysis. Clockwise: Mojave desert tortoise (Gopherus agassizii) (Elizabeth Fairbank, CLLC), White-tailed deer (Odocoileus virginianus) (N Hetherington, WTI/MSU), Wolf (Canus lupus) (Jim Peako, NPS), and Elk (Cervus elaphus) (N Hetherington WTI/MSU). . . . . . . . . . . . . . . . . 12 Figure 5: A variety of large and small wild animal species, free ranging livestock, and feral horses and donkeys are addressed in the Literature Review. Red squirrel (Sciurus vulgaris) N Hetherington, WTI/MSU), Wild horses (Equus ferus) (Dreamstime), Painted turtle (Chrysemys picta) (C M Highsmith), Coyote (Canis latrans) (N Hetherington WTI/MSU), Moose (Alces alces) (Jim Peako, NPS), Bull snake (Pituophis catenifer sayi)(J W Frank, NPS), Elk (Cervus canadensis) (N Hetherington WTI/MSU), Pika (Ochotona princeps) (J Waller, NPS), Pine marten (Martes americana) (J W Frank, NPS), Holstein cow (Bos taurus) (Adobe stock), Tiger salamander (Ambystoma tigrinum) (N Herbert, NPS), Wolf (Canis lupus) (Jim Peako, NPS), Mojave desert tortoise (Gopherus agassizii) (F Deffner, USFWS), Bobcat (Lynx rufus) (Neal Herbert, NPS). . . . . . 14 Figure 6: Left: Mule deer (Odocoileus hemionus) on US95 overpass (NDOT). Right: Horses using underpass (NDOT). 17 Figure 7: A representation of the wildlife included in the cost benefit analysis – clockwise, Elk (Cervus elaphus) (N Hetherington WTI/MSU), Grizzly bear cubs (Ursus arctos horribilis) (NPS), Wolf (Canis lupus) (Jim Peaco, NPS), and Mojave desert tortoise (Gopherus agassizii) (Flo Deffner, USFWS). . . . . 19 Figure 8: Species of interest in the Minnesota study. Clockwise: Blandings turtle (Emydoidea blandingii) (Andrew Cannizzaro) and White-tail deer (Odocoileus virginianus) (N Hetherington, WTI/MSU), public information sign, (Christopher Smith, MnDOT). . . . . . . . . . . . . . . . . 21 Figure 9: Key findings from the Minnesota household survey. . . . . . . . . . . . . . . . . 22 Figure 10: A sampling of animals used in the project to estimate cost of the average collision. Elk (Cervus elaphus) (Jacob W Frank, NPS), Grizzly bear (Ursus arctos horribilis) (N Hetherington, WTI/MSU), Wolf (Canis lupus) (Jacob W Frank, NPS), Wild horses (Equus ferus) (NDOT), and domestic cattle (Bos taurus) (N Hetherington WTI/MSU). . . . . . . . . . . . . . . . . . . . 23 Figure 11: Location of study area and highways used to examine elk-vehicle collisions in the Central Canadian Rocky Mountains (TCH is Highway 1, the TransCanada Highway). . . . . . . . . . 29 Figure 12: Elk crossing a congested roadway. (Shutterstock) . . . . . . . . . . . . . . . . . 30 Figure 13: The five different types of crossing structure designs that were evaluated (Tony Clevenger, Overpass Adobe Stock). . . . . . . . . . . . . . . . . . . . . . . . . 31 54 Figures Figure 14: Common ungulates and large carnivores on, or near, roadways. Clockwise, Pronghorn (Antilocapra americana) (Shutterstock), Mule deer (Odocoileus hemionus) (iStock - N Hetherington, WTI/MSU) Elk (Cervus elaphus) (N Hetherington, WTI/MSU), Black bear (Ursus americanus) (Shutterstock) and, Mountain lion (Puma concolor) (iStock). . . . . . . . . . . 33 Figure 15: An example of an electrified barrier at a fence-end. (Marcel Huijser) . . . . . . . . . . . 34 Figure 16: Elevation view of the US-97 wildlife overpass. Not Drawn to scale . . . . . . . . . . . . 36 Figure 17: A photo and the dimensions in centimeters (cm) of the FRP or composite tub girder used to form the structure for the design of the wildlife overpass structure on US-97 in Siskiyou County, California (AIT Bridges). Not drawn to scale . . . . . . . . . . . . . . . . . . 37 Figure 18: Cross section of the wildlife overpass showing the layout of the girders, concrete deck, soil, drainage, and barriers on the bridge span in meters (m). Not drawn to scale . . . . . . . . . 37 Figure 19: Rendering of a recycled-plastic sound and light barrier installed on top of the FRP overpass on US-97. . 38 Figure 20: Male (left) and female (right) Yosemite toad (Anaxyrus canorus) (Maierpa, Wikipedia). . . . . . . 40 Figure 21: Left to right, top to bottom, Yosemite toad (Anaxyrus canorus) at a monolithic 5 mm diameter polyethylene fence. Vehicles driving on the Elevated Road Segment (ERS), 3D rendering of an ERS concept design (C Brehme, USGS et al). . . . . . . . . . . . . . . . . . . . . 41 Figure 22: A view of a jump-out from outside the exclusionary fencing. The concrete block wall is designed to be high enough to dissuade animals from entering the roadway corridor, yet low enough for animals inside to jump to the outside of the fenced roadway corridor (Marcel Huijser). . . . . . . 42 Figure 23: A view of a jump-out on the highway side of the fencing with a perpendicular fence that is designed to direct animals following the exclusionary fence to use the jump out (Marcel Huijser). . . . 43 Figure 24: A jump-out that is modified with a 2 in (5 cm) by 2 in (5 cm) bar for the design experiment (Marcel Huijser). 43 Figure 25: Clockwise: concrete underpass, internal structure/cover treatments, Granite spiny lizard (Sceloporus orcutti), California king snake (Lampropeltis californiae), and Rat (Rattus), (Photos: Cheryl Brehme and Robert Fisher, USGS). . . . . . . . . . . . . . . . . . . . 44 Figure 26: Summary of changes in underpass use by various species after the installation of internal structure/cover treatments. . . . . . . . . . . . . . . . . . . . . . . . 45 Figure 27: Typical large ungulate fence in North America, 8 ft tall, wooden posts and mesh-wire fence material, US Hwy 93 North, Montana, USA. Note that there is a dig barrier attached to the main fence material (e.g. for canids) (Marcel Huijser). . . . . . . . . . . . . . . . . . 47 Figure 28: Wildlife friendly livestock fence with smooth top and bottom wires, Montana, USA (Marcel Huijser). . . 48 55 Figures LIST OF TABLES Table 1: Distinctions between crash terms . . . . . . . . . . . . . . . . . . . . . . 11 Table 2: Summary of the ten most effective of the 24 mitigation measures reviewed in the literature review report; they had to achieve at least a 50% reduction in AVCs with large mammals. Each measure was evaluated to determine if it reduced the barrier effect of roads to wildlife movement. Green signifies highly effective, yellow indicates moderately effective and red signifies ineffective. . . . . . 14 Table 3: Estimated per-animal values, by species. . . . . . . . . . . . . . . . . . . . . 18 Table 4: Vehicle repair costs, average human injury costs and average human fatality costs per collision for deer, elk, and moose in 2007 and 2020. . . . . . . . . . . . . . . . . . . . . 22 Table 5: Summary of wildlife values and avoided collision costs in (2020 US dollars ($)) from both economic studies in the TPF that can be used for cost-benefit analyses (CBAs) of wildlife-vehicle collision (WVC) mitigation measures. . . . . . . . . . . . . . . . . . . . . . . . 23 Table 6: Total costs associated with large wild wildlife-vehicle collisions (in 2020 US dollars ($)). . . . . . . . 24 Table 7: Threshold values (in US dollars or crash rates) indicate when the costs of crashes involving three common ungulate species in North American are equal to the cost of the construction and maintenance of the mitigation measure. Four different types of mitigation measures are calculated. For the US dollar threshold values, a three percent discount rate*1 was used. . . . . . . . . . 24 Table 8: Suitability of different types of mitigation measures for selected small and medium sized mammal species. . 47 56 Tables