FOREWORD 

America’s highways allow people and products to travel to every corner of our nation. Along the 

way, these roads cut across the habitat of many native wildlife species. When these paths cross, 

collisions occur, and in greater numbers than most people realize. This presents a real danger to 

human safety as well as wildlife survival. State and local transportation agencies are looking for 

ways to find a balance among travel needs, human safety, and conserving wildlife. 

This national study details the causes and impacts of wildlife-vehicle collisions and identifies 

potential solutions to this growing safety problem. This Report to Congress focuses on tools, 

methods, and other measures that reduce the number of collisions between vehicles and large 

wildlife, such as deer, because these accidents present the greatest safety danger to travelers and 

cause the most damage. 

Michael F. Trentacoste 

Director, Office of Safety 

Research and Development 

Notice 

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for the use of 

the information contained in this document. This report does not constitute a standard, 

specification, or regulation. 

The U.S. Government does not endorse products or manufacturers. Trademarks or 

manufacturers’ names appear in this report only because they are considered essential to the 

objective of the document. 

Quality Assurance Statement 

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards 

and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its 

information. FHWA periodically reviews quality issues and adjusts its programs and processes to 

ensure continuous quality improvement. 
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Tony Clevenger 

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Canada 

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Brian L. Cypher 

c/o California State University 

Stanislaus, Endangered Species Recovery Program 

E-mail: bcypher@esrp.csustan.edu

Adam Ford 

c/o Banff Wildlife Crossings Project 

Western Transportation Institute-MSU Bozeman 

Banff National Park 

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Banff, AB T1L 1K2 

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Bethanie Walder 

636 Stoddard St. 

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TECHNICAL REPORT DOCUMENTATION PAGE 

1. Report No. 

FHWA-HRT-08-034 

2. Government Accession No. 3. Recipient’s Catalog No. 

4. Title and Subtitle 

Wildlife-Vehicle Collision Reduction Study: Report to Congress 

5. Report Date 

August 2008 

6. Performing Organization Code 

7. Author(s) 

M.P. Huijser, P. McGowen, J. Fuller, A. Hardy, A. Kociolek, A.P. Clevenger, 

D. Smith and R. Ament 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

Western Transportation Institute 

Montana State University 

P.O. Box 174250 

Bozeman, MT 59717 

Under contract to: 

The Louis Berger Group, Inc. 

412 Mount Kemble Avenue 

Morristown, NJ 07962 

11. Contract or Grant No. 

DTFH61-05-D-00018 

12. Sponsoring Agency Name and Address 

Federal Highway Administration 

Office of Safety Research and Development 

6300 Georgetown Pike 

McLean, VA 22101-2296 

13. Type of Report and Period Covered 

Final Report 

14. Sponsoring Agency Code 

15. Supplementary Notes 

Sponsoring groups were the Federal Highway Administration Office of Safety Research and Development (C. Tan, A. 

Zineddin, and H. Valadez), the Federal Highway Administration Office of Planning, Environment, and Realty (Water and 

Ecosystems Team) (D. Durbin, M. Gray, and P. Garrett), and the Federal Highway Administration Western Federal Lands 

Highway Division (B. Allen). Contracting Officer’s Technical Representative (COTR): Dennis Durbin. Contracting Officer 

Technical Manager (COTM): Abdul Zineddin. 

16. Abstract 

Under the SAFETEA-LU Congressional Bill, the Secretary of Transportation was directed to conduct a national wildlifevehicle collision (WVC) reduction study. The study was to advance the understanding of the causes and impacts of WVCs and 

identify solutions to this growing safety problem. 

This report contains the findings of this study, beginning with estimates on the current magnitude and trend for WVCs in the 

United States. Based on several national datasets, the study found that there are between one and two million WVCs annually in 

the United States and that the number is increasing. Estimates are provided for the costs associated with WVCs, and the impact 

of direct road mortality is described for 21 federally listed threatened and endangered species. The core of the report is an indepth review of over 34 WVC mitigation methods assembled from information obtained from hundreds of literature sources 

(both published and “gray” literature). Each mitigation measure is described in detail, and information including case studies,

benefits, costs, undesirable effects, and design guidelines is provided. The report also covers planning and design considerations 

and provides cost-benefit analyses for the mitigation methods that had sufficient data available to support these analyses. A 

working group of seven national experts provided input and evaluated the effectiveness of the mitigation methods, categorizing 

them as either recommended for implementation, recommended for future research, or not recommended for future research or 

implementation. A summary of their evaluation is included in this report. Recommendations for implementation of effective 

measures and for further investigation of promising mitigation measures are provided. 

17. Key Words 

animal-vehicle collisions, deer-vehicle collisions, 

endangered and threatened species, wildlife fencing, wildlife 

crossing structures, wildlife overpasses, wildlife 

underpasses, wildlife-vehicle collisions 

18. Distribution Statement 

No restrictions. This document is available to the public through 

the National Technical Information Service, Springfield, VA 

22161. 

19. Security Classif. (of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of Pages 

251 

22. Price 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 
 

 ii 
 iii 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY ...........................................................................................................1

WILDLIFE-VEHICLE COLLISIONS: A GROWING PROBLEM ON U.S. ROADS .........4

Isn’t This Just a Rural Problem? ......................................................................................... 4

How Many Accidents Are There? ...................................................................................... 4

Is the Number of Accidents Increasing? ............................................................................. 5

WHAT ARE THE CONSEQUENCES? THE COSTS AND IMPACTS TO DRIVERS AND 

ANIMALS .......................................................................................................................................7

Impacts on Travelers ........................................................................................................... 7

Impacts on Wildlife ............................................................................................................. 9

CAN THE NUMBER OF COLLISIONS BE REDUCED? METHODS FOR 

PREVENTING COLLISIONS ...................................................................................................12

Influencing Wildlife Behavior .......................................................................................... 12

Reducing Wildlife Population Size ................................................................................... 15

Modifying Driver Behavior .............................................................................................. 15

Planning and Design Methods .......................................................................................... 17

Which Methods Are Most Effective? ............................................................................... 18

ARE WE MAKING PROGRESS? CHALLENGES FACED BY 

TRANSPORTATION AGENCIES ............................................................................................18

Gaps in Knowledge, Insufficient Information, and Lack of Data ..................................... 18

Research and Evaluation of Mitigation Measures ............................................................ 19

Training ............................................................................................................................. 19

WHERE DO WE GO FROM HERE? OPPORTUNITIES AND NEXT STEPS ..................20

CHAPTER 1. INTRODUCTION ...............................................................................................23

CHAPTER 2. CAUSES AND CHARACTERISTICS OF WILDLIFE-VEHICLE 

COLLISIONS ...............................................................................................................................25

DATA SOURCES ..................................................................................................................25

NATIONAL CRASH DATABASES ....................................................................................27

Fatal Accident Reporting System ..................................................................................... 27

Highway Safety Information System ................................................................................ 27

General Estimates System................................................................................................. 29

Total Vehicle Miles Traveled ........................................................................................... 29

EVALUATION METHODOLOGIES .................................................................................30

TOTAL MAGNITUDE .........................................................................................................30

IS THE PROBLEM GROWING? .......................................................................................31

TEMPORAL DISTRIBUTIONS ..........................................................................................33

SEVERITY .............................................................................................................................36

FACILITY TYPE ..................................................................................................................38

TRAFFIC DENSITY AND SPEED .....................................................................................38

WEATHER .............................................................................................................................42

ANIMAL SPECIES ...............................................................................................................42

LANDSCAPE ADJACENT TO ROADS ............................................................................44

NUMBER OF VEHICLES AND COLLISION TYPE.......................................................45
 iv 

DEER POPULATION DENSITY ........................................................................................45

DRIVER CHARACTERISTICS ..........................................................................................46

SUMMARY ............................................................................................................................47

CHAPTER 3. ECONOMIC IMPACTS OF WILDLIFE-VEHICLE COLLISIONS ...........49

METHODS .............................................................................................................................49

AVERAGE ANIMAL-VEHICLE COLLISION ................................................................49

DEER-, ELK-, AND MOOSE-VEHICLE COLLISIONS .................................................50

VEHICLE REPAIR COSTS .................................................................................................50

HUMAN INJURIES ..............................................................................................................51

HUMAN FATALITIES .........................................................................................................52

TOWING, ACCIDENT ATTENDANCE, AND INVESTIGATION................................53

MONETARY VALUE OF ANIMALS ................................................................................53

REMOVAL AND DISPOSAL COSTS OF DEER CARCASSES ....................................54

OTHER COSTS .....................................................................................................................54

SUMMARY ............................................................................................................................55

CHAPTER 4. IMPACTS TO WILDLIFE ................................................................................57

THREATENED AND ENDANGERED SPECIES .............................................................58

METHODS .............................................................................................................................58

RESULTS ...............................................................................................................................59

Amphibians ....................................................................................................................... 62

Reptiles ............................................................................................................................. 62

Birds .................................................................................................................................. 66

Mammals........................................................................................................................... 69

Other Species .................................................................................................................... 70

Summary ........................................................................................................................... 70

CHAPTER 5. MITIGATION METHODS THAT ATTEMPT TO INFLUENCE 

DRIVER BEHAVIOR .................................................................................................................71

PUBLIC INFORMATION AND EDUCATION .................................................................72

ROADWAY WARNING SIGNS ..........................................................................................78

STANDARD WILDLIFE WARNING SIGNS ....................................................................80

Case Studies and Contacts ................................................................................................ 80

Direct Benefits .................................................................................................................. 81

Indirect Benefits ................................................................................................................ 81

Undesirable Effects ........................................................................................................... 81

Costs .................................................................................................................................. 81

Guidelines ......................................................................................................................... 81

LARGE, NONSTANDARD WILDLIFE WARNING SIGNS ..........................................81

Case Studies and Contacts ................................................................................................ 83

Direct Benefits .................................................................................................................. 84

Indirect Benefits ................................................................................................................ 84

Undesirable Effects ........................................................................................................... 84

Costs .................................................................................................................................. 84

Guidelines ......................................................................................................................... 84

SEASONAL WILDLIFE WARNING SIGNS ....................................................................85

Case Studies and Contacts ................................................................................................ 85
 v 

Direct Benefits .................................................................................................................. 86

Indirect Benefits ................................................................................................................ 86

Undesirable Effects ........................................................................................................... 86

Costs .................................................................................................................................. 86

Guidelines ......................................................................................................................... 86

ANIMAL DETECTION SYSTEMS ....................................................................................86

Case Studies and Contacts ................................................................................................ 89

Direct Benefits .................................................................................................................. 89

Indirect Benefits ................................................................................................................ 89

Undesirable Effects ........................................................................................................... 89

Costs .................................................................................................................................. 89

Guidelines ......................................................................................................................... 90

IN-VEHICLE WARNINGS: ROADSIDE ANIMAL DETECTION SYSTEM 

LINKED TO ON-BOARD COMPUTER WARNING SYSTEM .....................................90

Case Studies and Contacts ................................................................................................ 90

Direct Benefits .................................................................................................................. 90

Indirect Benefits ................................................................................................................ 90

Undesirable Effects ........................................................................................................... 90

Costs .................................................................................................................................. 91

Guidelines ......................................................................................................................... 91

IN-VEHICLE WARNINGS: ON-BOARD ANIMAL DETECTORS ..............................91

Case Studies and Contacts ................................................................................................ 91

Direct Benefits .................................................................................................................. 91

Indirect Benefits ................................................................................................................ 91

Undesirable Effects ........................................................................................................... 91

Costs .................................................................................................................................. 91

Guidelines ......................................................................................................................... 91

INCREASE VISIBILITY OF ANIMALS TO DRIVERS .................................................92

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: ROADWAY LIGHTING ....92

Case Studies and Contacts ................................................................................................ 93

Direct Benefits .................................................................................................................. 93

Indirect Benefits ................................................................................................................ 93

Undesirable Effects ........................................................................................................... 93

Costs .................................................................................................................................. 94

Guidelines ......................................................................................................................... 94

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: VEGETATION 

REMOVAL .............................................................................................................................94

Case Studies and Contacts ................................................................................................ 95

Direct Benefits .................................................................................................................. 95

Indirect Benefits ................................................................................................................ 95

Undesirable Effects ........................................................................................................... 95

Costs .................................................................................................................................. 95

Guidelines ......................................................................................................................... 96

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: WIDER STRIPING .............96

Case Studies and Contacts ................................................................................................ 96

Direct Benefits .................................................................................................................. 96
 vi 

Indirect Benefits ................................................................................................................ 96

Undesirable Effects ........................................................................................................... 96

Costs .................................................................................................................................. 96

Guidelines ......................................................................................................................... 97

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: REFLECTIVE 

COLLARS FOR ANIMALS .................................................................................................97

Case Studies and Contacts ................................................................................................ 97

Direct Benefits .................................................................................................................. 97

Indirect Benefits ................................................................................................................ 97

Undesirable Effects ........................................................................................................... 97

Costs .................................................................................................................................. 97

Guidelines ......................................................................................................................... 97

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: REDUCE HEIGHT OF 

SNOWBANKS........................................................................................................................98

Case Studies and Contacts ................................................................................................ 98

Direct Benefits .................................................................................................................. 98

Indirect Benefits ................................................................................................................ 98

Undesirable Effects ........................................................................................................... 98

Costs .................................................................................................................................. 98

Guidelines ......................................................................................................................... 98

REDUCE TRAFFIC VOLUME ON ROAD NETWORK .................................................98

Case Studies and Contacts ................................................................................................ 99

Direct Benefits .................................................................................................................. 99

Indirect Benefits ................................................................................................................ 99

Undesirable Effects ........................................................................................................... 99

Costs .................................................................................................................................. 99

Guidelines ......................................................................................................................... 99

TEMPORARY ROAD CLOSURES ..................................................................................100

Case Studies and Contacts .............................................................................................. 100

Direct Benefits ................................................................................................................ 100

Indirect Benefits .............................................................................................................. 100

Undesirable Effects ......................................................................................................... 100

Costs ................................................................................................................................ 100

Guidelines ....................................................................................................................... 100

REDUCE VEHICLE SPEED .............................................................................................100

REDUCE VEHICLE SPEED BY REDUCING THE POSTED SPEED LIMIT ..........102

Case Studies and Contacts .............................................................................................. 103

Guidelines ....................................................................................................................... 103

Direct Benefits ................................................................................................................ 103

Indirect Benefits .............................................................................................................. 104

Undesirable Effects ......................................................................................................... 104

Costs ................................................................................................................................ 104

REDUCE VEHICLE SPEED BY TRAFFIC CALMING/REDUCING 

DESIGN SPEED ..................................................................................................................104

Case Studies and Contacts .............................................................................................. 107

Direct Benefits ................................................................................................................ 107
 vii 

Indirect Benefits .............................................................................................................. 107

Undesirable Effects ......................................................................................................... 107

Costs ................................................................................................................................ 107

Guidelines ....................................................................................................................... 107

REDUCE VEHICLE SPEED BY POSTING ADVISORY SPEED SIGNS ...................107

WILDLIFE CROSSING GUARDS ...................................................................................108

Case Studies and Contacts .............................................................................................. 108

Direct Benefits ................................................................................................................ 108

Indirect Benefits .............................................................................................................. 108

Undesirable Effects ......................................................................................................... 108

Costs ................................................................................................................................ 108

Guidelines ....................................................................................................................... 108

CHAPTER 6. MITIGATION METHODS THAT SEEK TO INFLUENCE ANIMAL 

BEHAVIOR ................................................................................................................................109

DEER REFLECTORS AND MIRRORS ..........................................................................109

Case Studies and Contacts .............................................................................................. 110

Direct Benefits ................................................................................................................ 111

Indirect Benefits .............................................................................................................. 111

Undesirable Effects ......................................................................................................... 111

Costs ................................................................................................................................ 111

Guidelines ....................................................................................................................... 111

AUDIO SIGNALS IN RIGHT OF WAY OR ATTACHED TO VEHICLE (DEER 

WHISTLES) .........................................................................................................................111

Case Studies and Contacts .............................................................................................. 112

Direct Benefits ................................................................................................................ 113

Indirect Benefits .............................................................................................................. 113

Undesirable Effects ......................................................................................................... 113

Costs ................................................................................................................................ 113

Guidelines ....................................................................................................................... 113

OLFACTORY REPELLENTS ..........................................................................................113

Case Studies and Contacts .............................................................................................. 114

Direct Benefits ................................................................................................................ 114

Indirect Benefits .............................................................................................................. 114

Undesirable Effects ......................................................................................................... 115

Costs ................................................................................................................................ 115

Guidelines ....................................................................................................................... 115

DEER FLAGGING MODELS ...........................................................................................115

Case Studies and Contacts .............................................................................................. 115

Direct Benefits ................................................................................................................ 116

Indirect Benefits .............................................................................................................. 116

Undesirable Effects ......................................................................................................... 116

Costs ................................................................................................................................ 116

Guidelines ....................................................................................................................... 116

HAZING ...............................................................................................................................116

Case Studies and Contacts .............................................................................................. 117

Direct Benefits ................................................................................................................ 117
 viii 

Indirect Benefits .............................................................................................................. 117

Undesirable Effects ......................................................................................................... 117

Costs ................................................................................................................................ 117

Guidelines ....................................................................................................................... 117

DEICING ALTERNATIVES .............................................................................................117

Case Studies and Contacts .............................................................................................. 118

Direct Benefits ................................................................................................................ 118

Indirect Benefits .............................................................................................................. 118

Undesirable Effects ......................................................................................................... 119

Costs ................................................................................................................................ 119

Guidelines ....................................................................................................................... 119

INTERCEPT FEEDING .....................................................................................................119

Case Studies and Contacts .............................................................................................. 119

Direct Benefits ................................................................................................................ 119

Indirect Benefits .............................................................................................................. 120

Undesirable Effects ......................................................................................................... 120

Costs ................................................................................................................................ 120

Guidelines ....................................................................................................................... 120

INFLUENCE SPECIES COMPOSITION OR MINIMIZE NUTRITIONAL 

VALUE OF VEGETATION IN RIGHT OF WAY ..........................................................120

Case Studies and Contacts .............................................................................................. 121

Direct Benefits ................................................................................................................ 121

Indirect Benefits .............................................................................................................. 121

Undesirable Effects ......................................................................................................... 121

Costs ................................................................................................................................ 121

Guidelines ....................................................................................................................... 121

REMOVE CARCASSES ALONG TRANSPORTATION CORRIDOR .......................121

Case Studies and Contacts .............................................................................................. 122

Direct Benefits ................................................................................................................ 122

Indirect Benefits .............................................................................................................. 122

Undesirable Effects ......................................................................................................... 122

Costs ................................................................................................................................ 122

Guidelines ....................................................................................................................... 122

INCREASE MEDIAN WIDTH ..........................................................................................122

Case Studies and Contacts .............................................................................................. 123

Direct Benefits ................................................................................................................ 123

Indirect Benefits .............................................................................................................. 123

Undesirable Effects ......................................................................................................... 123

Costs ................................................................................................................................ 123

Guidelines ....................................................................................................................... 123

CHAPTER 7. MITIGATION METHODS THAT SEEK TO REDUCE WILDLIFE 

POPULATION SIZE .................................................................................................................125

WILDLIFE CULLING .......................................................................................................126

Case Studies and Contacts .............................................................................................. 126

Direct Benefits ................................................................................................................ 127

Indirect Benefits .............................................................................................................. 127
 ix 

Undesirable Effects ......................................................................................................... 127

Costs ................................................................................................................................ 127

Guidelines ....................................................................................................................... 128

WILDLIFE RELOCATION ...............................................................................................128

Case Studies and Contacts .............................................................................................. 128

Direct Benefits ................................................................................................................ 128

Indirect Benefits .............................................................................................................. 128

Undesirable Effects ......................................................................................................... 128

Costs ................................................................................................................................ 129

Guidelines ....................................................................................................................... 129

ANTI-FERTILITY TREATMENT ...................................................................................129

Case Studies and Contacts .............................................................................................. 130

Direct Benefits ................................................................................................................ 130

Indirect Benefits .............................................................................................................. 130

Undesirable Effects ......................................................................................................... 130

Costs ................................................................................................................................ 131

Guidelines ....................................................................................................................... 131

HABITAT ALTERATION AWAY FROM THE ROAD ................................................131

Case Studies and Contacts .............................................................................................. 132

Direct Benefits ................................................................................................................ 132

Indirect Benefits .............................................................................................................. 132

Undesirable Effects ......................................................................................................... 132

Costs ................................................................................................................................ 132

Guidelines ....................................................................................................................... 132

CHAPTER 8. MITIGATION METHODS THAT SEEK TO PHYSICALLY SEPARATE 

ANIMALS FROM THE ROADWAY .....................................................................................133

WILDLIFE FENCING ........................................................................................................133

Case Studies and Contacts .............................................................................................. 135

Direct Benefits ................................................................................................................ 135

Indirect Benefits .............................................................................................................. 135

Undesirable Effects ......................................................................................................... 136

Costs ................................................................................................................................ 137

Guidelines ....................................................................................................................... 137

ADDRESSING UNDESIRABLE EFFECTS OF WILDLIFE FENCING .....................138

SAFE CROSSING OPPORTUNITIES: GAPS IN FENCE ............................................139

Case Studies and Contacts .............................................................................................. 139

Direct Benefits ................................................................................................................ 141

Indirect Benefits .............................................................................................................. 141

Undesirable Effects ......................................................................................................... 141

Costs ................................................................................................................................ 141

Guidelines ....................................................................................................................... 141

SAFE CROSSING OPPORTUNITIES: WILDLIFE UNDERPASSES AND 

OVERPASSES .....................................................................................................................141

Case Studies and Contacts .............................................................................................. 144

Direct Benefits ................................................................................................................ 144

Indirect Benefits .............................................................................................................. 144
 x 

Undesirable Effects ......................................................................................................... 144

Costs ................................................................................................................................ 144

Guidelines ....................................................................................................................... 145

ESCAPE OPPORTUNITIES FROM RIGHT OF WAY .................................................145

ESCAPE OPPORTUNITIES FROM RIGHT OF WAY: JUMP-OUTS OR ESCAPE 

RAMPS .................................................................................................................................145

Case Studies and Contacts .............................................................................................. 146

Direct Benefits ................................................................................................................ 147

Indirect Benefits .............................................................................................................. 147

Undesirable Effects ......................................................................................................... 147

Costs ................................................................................................................................ 147

Guidelines ....................................................................................................................... 147

ESCAPE OPPORTUNITIES FROM RIGHT OF WAY: ONE-WAY GATES ............147

Case Studies and Contacts .............................................................................................. 149

Direct Benefits ................................................................................................................ 149

Indirect Benefits .............................................................................................................. 149

Undesirable Effects ......................................................................................................... 149

Costs ................................................................................................................................ 149

Guidelines ....................................................................................................................... 150

MITIGATION FOR FENCE ENDS: BOULDERS BETWEEN FENCE AND 

ROADWAY ..........................................................................................................................150

Case Studies and Contacts .............................................................................................. 150

Direct Benefits ................................................................................................................ 150

Indirect Benefits .............................................................................................................. 151

Undesirable Effects ......................................................................................................... 151

Costs ................................................................................................................................ 151

Guidelines ....................................................................................................................... 151

MITIGATION FOR FENCE ENDS: ANIMAL DETECTION SYSTEMS ..................152

Case Studies and Contacts .............................................................................................. 152

Direct Benefits ................................................................................................................ 152

Indirect Benefits .............................................................................................................. 152

Undesirable Effects ......................................................................................................... 152

Costs ................................................................................................................................ 152

Guidelines ....................................................................................................................... 152

LANDSCAPE AESTHETICS OF WILDLIFE FENCING .............................................152

Case Studies and Contacts .............................................................................................. 153

Direct Benefits ................................................................................................................ 153

Indirect Benefits .............................................................................................................. 153

Undesirable Effects ......................................................................................................... 153

Costs ................................................................................................................................ 153

Guidelines ....................................................................................................................... 153

REDUCE MORTALITY RISK OF WILDLIFE FENCING ..........................................153

Case Studies and Contacts .............................................................................................. 153

Direct Benefits ................................................................................................................ 154

Indirect Benefits .............................................................................................................. 154

Undesirable Effects ......................................................................................................... 154
 xi 

Costs ................................................................................................................................ 154

Guidelines ....................................................................................................................... 154

GAPS CAUSED BY ACCESS ROADS .............................................................................154

GAPS CAUSED BY ACCESS ROADS: GATES .............................................................154

Case Studies and Contacts .............................................................................................. 154

Direct Benefits ................................................................................................................ 154

Indirect Benefits .............................................................................................................. 155

Undesirable Effects ......................................................................................................... 155

Costs ................................................................................................................................ 155

Guidelines ....................................................................................................................... 155

GAPS CAUSED BY ACCESS ROADS: CATTLE OR WILDLIFE GUARDS ............155

Case Studies and Contacts .............................................................................................. 156

Direct Benefits ................................................................................................................ 156

Indirect Benefits .............................................................................................................. 156

Undesirable Effects ......................................................................................................... 157

Costs ................................................................................................................................ 157

Guidelines ....................................................................................................................... 157

ACCESS FOR PEOPLE SUCH AS HIKERS, SKIERS, CYCLERS, AND FISHERS 157

Case Studies and Contacts .............................................................................................. 158

Direct Benefits ................................................................................................................ 158

Indirect Benefits .............................................................................................................. 158

Undesirable Effects ......................................................................................................... 158

Costs ................................................................................................................................ 159

Guidelines ....................................................................................................................... 159

BOULDERS IN THE RIGHT OF WAY ...........................................................................159

Case Studies and Contacts .............................................................................................. 160

Direct Benefits ................................................................................................................ 160

Indirect Benefits .............................................................................................................. 160

Undesirable Effects ......................................................................................................... 160

Costs ................................................................................................................................ 160

Guidelines ....................................................................................................................... 161

LONG TUNNELS AND LONG BRIDGES OVER LANDSCAPE ................................161

Case Studies and Contact ................................................................................................ 162

Direct Benefits ................................................................................................................ 163

Indirect Benefits .............................................................................................................. 163

Undesirable Effects ......................................................................................................... 163

Costs ................................................................................................................................ 163

Guidelines ....................................................................................................................... 163

WILDLIFE UNDERPASSES AND OVERPASSES ........................................................163

CHAPTER 9. PLANNING AND DESIGN CONSIDERATIONS ........................................165

IDENTIFYING AND PRIORITIZING WVC PROBLEM AREAS ..............................165

Case Studies and Contacts .............................................................................................. 167

DATA COLLECTION AND MONITORING ..................................................................168

Case Studies and Contacts .............................................................................................. 168

ALTERNATIVE ALIGNMENT, ROAD REMOVAL, OR NO NEW ROAD ..............169

Case Studies and Contacts .............................................................................................. 171
 xii 

CONSIDERATION OF DESIGN FEATURES ................................................................171

CHAPTER 10. EVALUATION OF MITIGATION METHODS BY TECHNICAL 

WORKING GROUP .................................................................................................................173

CHAPTER 11. GAPS IN CURRENT KNOWLEDGE ..........................................................181

DATA ISSUES .....................................................................................................................181

ANALYSIS ISSUES.............................................................................................................181

NEEDED TOOLS ................................................................................................................182

SUMMARY ..........................................................................................................................182

CHAPTER 12. COST-BENEFIT ANALYSES OF DEER COLLISION REDUCTION 

MEASURES ...............................................................................................................................183

CHAPTER 13. CONCLUSION ................................................................................................189

APPENDIX: EXPERTS CONSULTED FOR ENDANGERED SPECIES ACT LIST ......191

ACKNOWLEDGEMENTS ......................................................................................................197

REFERENCES ...........................................................................................................................199
 xiii 

LIST OF FIGURES 

Figure ES1. Photo. A collision with a white-tailed deer can result in extensive property 

damage ............................................................................................................................................ 1

Figure ES2. Photo. Standard deer warning sign along Montana Highway 83 ............................... 2

Figure ES3. Photo. Seasonal deer migration sign in Utah .............................................................. 2

Figure ES4. Photo. Wildlife warning and advisory speed limit reduction signs triggered by an 

animal detection system in ‘t Harde, The Netherlands ................................................................... 3

Figure ES5. Graph. Human injury from AVCs (primarily deer) .................................................... 5

Figure ES6. Graph. Animal species involved in fatal (to human) collisions, Maine ..................... 5

Figure ES7. Graph. Total vehicle crashes ....................................................................................... 6

Figure ES8. Graph. Total AVCs (including wildlife and domestic animals) ................................. 6

Figure ES9. Photo. A mule deer is hit by a vehicle in Big Bend National Park, TX ..................... 8

Figure ES10. Photo. Hawaiian goose warning sign ...................................................................... 10

Figure ES11. Photo. Desert tortoise .............................................................................................. 10

Figure ES12. Photo. San Joaquin kit fox ...................................................................................... 11

Figure ES13. Photo. Wildlife fencing along Interstate 90 near Bozeman, MT ........................... 12

Figure ES14. Photo. Wildlife underpass in southern Florida that allows for ecosystem process 

(hydrology) as well as wildlife use, including the Florida panther ............................................... 13

Figure ES15. Photo. Large culvert with vegetative cover and fencing on Highway 1 

in Canada ...................................................................................................................................... 14

Figure ES16. Photo. Long bridge on Arizona Highway 260 constructed in such a way as to 

minimize the impact to soil and vegetation .................................................................................. 15

Figure ES17. Photo. Permanently flashing Florida black bear warning signs in the Ocala 

National Forest, FL ....................................................................................................................... 16

Figure ES18. Photo. Roadkill observation collection system (ROCS), a GPS-enabled PDA for 

animal carcass data collection ....................................................................................................... 19

Figure ES19. Photo. Animal detection system along U.S. Highway 191 in Yellowstone National 

Park, MT ....................................................................................................................................... 20

Figure ES20. Photo. Animal detection test-bed used to test the reliability of multiple animal 

detection systems, Lewistown, MT .............................................................................................. 21

Figure 1. Graph. Annual WVCs estimated by insurance industry ................................................ 26

Figure 2. Graph. Total vehicle crashes ......................................................................................... 32

Figure 3. Graph. Total AVCs (including wildlife and domestic animals) .................................... 32

Figure 4. Graph. Annual crash rate for AVCs (GES and VMT data) ........................................... 33

Figure 5. Graph. Annual distribution of AVCs............................................................................. 34

Figure 6. Graph. Annual distribution for other/domestic animal-vehicle collisions in 

CA, WA, IL, ME, and UT (HSIS data) ........................................................................................ 34

Figure 7. Graph. Annual distributions for moose and bear collisions in Maine (HSIS data) ....... 35

Figure 8. Graph. Time-of-day distribution ................................................................................... 35

Figure 9. Graph. Severity distribution for AVCs (GES data) ....................................................... 36

Figure 10. Graph. Severity distribution for all crashes (GES data) .............................................. 37

Figure 11. Graph. Severity distribution of moose-vehicle collisions in Maine (HSIS data) ........ 37
 xiv 

Figure 12. Graph. AVCs by number of lanes (GES data) ............................................................ 38

Figure 13. Graph. Theoretical relationship between traffic volume, successful wildlife crossings, 

and road mortality (adapted from Seiler) ...................................................................................... 39

Figure 14. Graph. Crashes by ADT (HSIS data) .......................................................................... 40

Figure 15. Graph. Distribution by posted speed limit (GES data) ................................................ 41

Figure 16. Graph. Distribution of fatal crashes by posted speed limit (FARS data) .................... 42

Figure 17. Graph. Animal species involved in collisions in California (HSIS data) .................... 43

Figure 18. Graph. Animal species involved in collisions in Maine (HSIS data) .......................... 43

Figure 19. Graph. Animal species involved with collisions in Washington (HSIS data) ............. 44

Figure 20. Graph. Fatal AVCs by collision type (FARS data) ..................................................... 45

Figure 21. Graph. Age distribution for all crashes and AVCs (HSIS data) .................................. 47

Figure 22. Photo. Desert tortoise .................................................................................................. 63

Figure 23. Photo. Fences lead gopher tortoises towards a culvert along Highway 63 in Green 

County, south of Leakesville, MS................................................................................................. 64

Figure 24. Photo. A section of the Mobile Bay Causeway that has relatively many road-killed 

Alabama red-bellied turtles ........................................................................................................... 65

Figure 25. Photo. Road-killed Alabama red-bellied turtle ............................................................ 65

Figure 26. Photo. “Do Not Feed Nene” sign ................................................................................ 68

Figure 27. Photo. Hawaiian goose (nene) warning sign ............................................................... 68

Figure 28. Photo. Example of bumper sticker for a driver awareness campaign to reduce WVCs 

in Jasper National Park, Canada ................................................................................................... 73

Figure 29. Photo. Roadside billboard along highway in Jasper National Park, Canada ............... 74

Figure 30. Photo. Poster created by NASA’s John F. Kennedy Space Center as part of its 

RoadKill Prevention Program ....................................................................................................... 75

Figure 31. Photo. Poster produced by the Maine Department of Transportation. ........................ 76

Figure 32. Graph. Driver age distribution for all crashes and AVCs (HSIS data) ....................... 78

Figure 33. Flow chart. Warning signs and driver response .......................................................... 79

Figure 34. Photo. Standard deer warning sign along Montana Highway 83 ................................ 80

Figure 35. Photo. Large enhanced warning sign for bighorn sheep along State Highway 75 

in Idaho ......................................................................................................................................... 82

Figure 36. Photo. Large enhanced elk warning sign along the Trans-Canada Highway in 

Banff National Park, Canada ........................................................................................................ 83

Figure 37. Photo. Seasonal deer migration sign in Utah ............................................................... 85

Figure 38. Photo. Animal detection system along Highway 191 in Yellowstone 

National Park, MT ........................................................................................................................ 87

Figure 39. Photo. Advisory speed sign in The Netherlands located at a gap in exclusionary 

wildlife fencing ........................................................................................................................... 102

Figure 40. Graph. Roadkill by posted speed limit in Yellowstone ............................................. 105

Figure 41. Photo. Speed bumps used to reduce WVCs in Australia ........................................... 106

Figure 42. Photo. Wildlife fence along Interstate 90 near Bozeman, MT .................................. 134

Figure 43. Photo. Gap in a wildlife fence accompanied by wildlife warning signs and 

advisory speed limit reduction, The Netherlands ....................................................................... 140

Figure 44. Photo. Gap in a wildlife fence combined with an animal detection system, 

wildlife warning signs, and advisory speed limit reduction, The Netherlands ........................... 140

Figure 45. Photo. Wildlife underpass along U.S. Highway 93 on the Flathead Indian 

Reservation, MT ......................................................................................................................... 142
 xv 

Figure 46. Photo. Wildlife overpass in Banff National Park, Alberta, Canada .......................... 143

Figure 47. Photo. Underpass in southern Florida that allows for ecosystem processes 

(hydrology) as well as wildlife use, including the Florida panther ............................................. 143

Figure 48. Photo. Jump-out or escape ramp along U.S. Highway 93 on the Flathead Indian 

Reservation, MT ......................................................................................................................... 146

Figure 49. Photo. One-way elk gate in British Columbia, Canada ............................................. 148

Figure 50. Photo. One-way Eurasian badger gate, The Netherlands .......................................... 149

Figure 51. Photo. The boulder field at the fence end at Dead Man’s Flats along the 

Trans-Canada Highway east of Canmore, Alberta, Canada ....................................................... 151

Figure 52. Photo. Wildlife guard along U.S. Highway 93 on the Flathead Indian 

Reservation, MT ......................................................................................................................... 156

Figure 53. Photo. Angled opening in fence allowing access for people along U.S. 

Highway 93, MT ......................................................................................................................... 157

Figure 54. Photo. Swing gate in fence (spring loaded) allowing access for people, along 

the Trans-Canada Highway in Banff National Park, Alberta, Canada ....................................... 158

Figure 55. Photo. Large boulders pPlaced in the right of way as a barrier to elk and deer 

along State Route 260 in Arizona ............................................................................................... 159

Figure 56. Photo. Large boulders placed in the right of way as a barrier to elk and deer 

with a view of State Route 260 (under construction) in Arizona ............................................... 160

Figure 57. Photo. Long bridge on Arizona State Route 260 constructed in such a way as 

to minimize the impact to soil and vegetation ............................................................................ 161

Figure 58. Photo. Long bridges do not have to be excessively large to provide ample space.... 162

Figure 59. Photo. Road removal in progress in Belgium (note that a path for pedestrians 

and bicyclists remains in place.) ................................................................................................. 171

Figure 60. Graph. Annual balance and collision reduction for the different mitigation 

measures ...................................................................................................................................... 188
 xvi 

LIST OF TABLES 

Table 1. Summary of HSIS data characteristics from different states .......................................... 28

Table 2. Five-year crash totals for HSIS states ............................................................................. 30

Table 3. Total annual magnitude of WVCs from various sources ................................................ 31

Table 4. Estimated costs for property damage, human injuries, and human fatalities for the 

average AVC ................................................................................................................................. 50

Table 5. Costs for types of human injuries for the average deer-, elk-, and moose-vehicle 

collision ......................................................................................................................................... 52

Table 6. Summary of estimated costs of a WVC for a deer, elk, and moose ............................... 55

Table 7. Threatened and endangered species in the United States for which direct road 

mortality is among the major threats to the survival probability of the species ........................... 60

Table 8. Collisions with large animals before and after detection system installation in 

Switzerland ................................................................................................................................... 88

Table 9. Technical working group members .............................................................................. 173

Table 10. Technical working group rankings ............................................................................. 176

Table 11. Technical working group recommendations ............................................................... 178

Table 12. Summary cost-benefit of mitigation measures for five DVCs per km per yr ............. 184
 xvii 

LIST OF ABBREVIATIONS AND SYMBOLS 

ABBREVIATIONS FOR COLLISIONS WITH ANIMALS

AVC Animal-vehicle collisions. Collisions with wild and domestic animals in cases 

where domestic animals could not be separated from the dataset. 

WVC Wildlife-vehicle collisions. Collisions with all species of wild animals. 

DVC Deer-vehicle collisions. WVCs that involve only deer. A separate term is used for 

deer and no other specific type of animal because deer account for a majority of 

WVCs when data are available. When information is specific to one type of 

animal other than deer, no abbreviation is used (e.g., moose-vehicle collision). 

ABBREVIATIONS 

ADT Average daily traffic, is defined as the total volume during a given time period (in 

days), greater than 1 day and less than 1 year, divided by the number of days in 

that time period.(1) In this report the time period is always 1 year. 

AASHTO American Association of State Highway and Transportation Officials 

ADOT Arizona Department of Transportation 

BTS Bureau of Transportation Statistics of the U.S. Department of Transportation 

CaMg Chemical formula for calcium magnesium acetate, a common alternative to road 

salt for deicing. 

CSD/CSS Context-sensitive design/context-sensitive solutions, is a planning and/or design 

strategy that attempts to consider scenic, aesthetic, historic, environmental, and 

community values. 

DOT see State DOT 

DMS Dynamic message signs, also referred to as variable message signs 

FARS Fatal Accident Reporting System, is a national dataset that includes all crashes 

with a human fatality. 

FHWA Federal Highway Administration 

GES General Estimates System, is a dataset that enables estimates of national crash 

numbers based on a national sample. 

GIS Geographic Information Systems, which relates to spatial data standards and in 

some cases, sets of spatial data. 

GPS Global Positioning System 
 xviii 

HSIS Highway Safety Information System, is a dataset that includes all reported crashes 

from Washington, California, Illinois, Maine, Michigan, Minnesota, North 

Carolina, Ohio, and Utah. 

IUCN International Union for Conservation of Nature and Natural Resources 

km/h Kilometers per hour 

LED Light-emitting diode, a technology used for, among other things, lighted signs and 

flashers. 

MNDOT Minnesota Department of Transportation 

mi/h Miles per hour 

MUTCD Manual on Uniform Traffic Control Devices, which provides national guidance 

and standards for, among other things, warning signs and signals. 

NaCl Chemical formula for sodium chloride (salt), a common deicing chemical 

NCHRP National Cooperative Highway Research Program 

NPS National Park Service 

NYSDOT New York State Department of Transportation 

ROW Right of way, refers to the area owned by the transportation agency, including the 

roadside. 

SAFETEA-LU Safe, Accountable, Flexible, and Efficient Transportation Equity Act: A Legacy 

for Users, which is the primary congressional bill for surface transportation 

programs, signed by President George W. Bush in August 2005. 

State DOT State department of transportation in general (i.e., not a specific state) 

USDOT U.S. Department of Transportation 

USFWS U.S. Fish and Wildlife Service 

VMT Vehicle miles traveled 

SYMBOLS 

$ Followed by a numerical value refers to dollar value. Unless otherwise specified, 

reported values are in U.S. dollars. 

Can$ Followed by a numerical value refer to Canadian dollars. 

€ Followed by a numerical value refers to Euros. 
 1 

EXECUTIVE SUMMARY 

America’s highways allow people and products to travel to every corner of our nation. Along the 

way, these roads cross through the habitat of many native wildlife species. When these paths 

intersect, collisions can occur, and in greater numbers than most people realize. Based on the 

results of this study, there are an estimated one to two million collisions between cars and large 

animals every year in the United States. This presents a real danger to human safety as well as 

wildlife survival. State and local transportation agencies are looking for ways to meet the needs 

of the traveling public, maintain human safety, and conserve wildlife. 

Under Section 1119 (n) of the Safe, Accountable, Flexible, and Efficient Transportation Equity 

Act: A Legacy for Users (SAFETEA-LU), the U.S. Congress directed the Secretary of 

Transportation to conduct a national wildlife-vehicle collision (WVC) study. This study details 

the causes and impacts of WVCs and identifies potential solutions to this growing safety 

problem. The report focuses on mitigation methods that reduce the number of collisions between 

vehicles and large wildlife, such as deer, because these accidents present the greatest safety 

danger to travelers and cause the most damage (figure ES1). 

This summary of the full report highlights the major findings and serves as an introduction to the 

issue of WVCs. Major findings include: 

• WVCs are a growing problem and represent an increasing percentage of the accidents on 

our roads. 

Figure ES1. Photo. A collision with a white-tailed deer can result in extensive property 

damage (copyright: Marcel Huijser). 

• WVCs have significant impacts on drivers and wildlife. For motorists, WVCs present a 

safety danger and can result in significant costs from vehicle damage. For animals, 

WVCs often kill the individual animals and can even pose a threat to the very survival of 
 2 

certain species. This study identified 21 federally listed threatened or endangered animal 

species in the United States for which road mortality is documented as one of the major 

threats to their survival. 

• There are no simple solutions to reducing WVCs. In this study, the research team 

reviewed 34 mitigation techniques, a number of which are effective in reducing WVCs, 

show promise, or are considered good practice, including integrated planning efforts, 

wildlife fencing and wildlife crossing structures, animal detection systems and public 

information and education (figure ES2 through figure ES4). 

Figure ES2. Photo. Standard deer warning sign along Montana Highway 83 

(copyright: Marcel Huijser). 

Figure ES3. Photo. Seasonal deer migration sign in Utah 

(copyright: Marcel Huijser). 
 3 

Figure ES4. Photo. Wildlife warning and advisory speed limit reduction signs triggered by 

an animal detection system in ‘t Harde, The Netherlands (copyright: Marcel Huijser). 

• A major challenge that must be addressed before WVCs can be systematically reduced is 

improving the consistency and precision of data collection on WVCs. Inconsistent and 

imprecise data make it difficult to identify and prioritize road sections that require 

mitigation. 

This document concludes with recommendations for further action. Policymakers who are 

interested in reducing WVCs can begin by considering the following actions: 

• Incorporate WVC reduction into the early stages of planning and design for 

transportation projects. 

• Develop and implement guidelines and standards for collecting data on and reporting 

WVCs. 

• Develop and implement guidelines for evaluating mitigation methods. 

• Evaluate the effectiveness of mitigation methods that have been recommended for further 

research. 

• Implement (or install) proven mitigation measures where appropriate. 

• Develop and apply wildlife population models to assist with locating and designing 

mitigation methods. 
 4 

• Conduct technology transfer to State departments of transportation, resource agencies, 

and other transportation professionals regarding the findings of this study. A handbook 

and training course on WVC reduction techniques will be developed by August 2008, 

which will help in making this information available to practitioners. 

WILDLIFE-VEHICLE COLLISIONS: A GROWING PROBLEM ON U.S. ROADS 

Isn’t This Just a Rural Problem? 

According to data from national crash databases, 89 percent of all WVCs (2001–2005) were on 

two-lane roads. This might lead some people to conclude that WVCs are only a problem in 

remote, rural locations, but two-lane roads and WVCs are also prevalent in areas where many 

people live and commute to work in nearby cities. Such two-lane highways are critical travel 

corridors, and, in the United States, drivers use two-lane roadways for the majority of the total 

highway miles they travel. Therefore, WVCs are a challenge in every state and for almost all 

drivers across the country. 

How Many Accidents Are There? 

Estimates of the total number of WVCs are based on several sources, including crash statistics 

(from police and highway patrol report information), roadside carcass counts, insurance industry 

claims information, and interviews with the public. 

National crash databases estimate the total number of reported collisions at 300,000 per year. 

However, most researchers believe that WVCs are substantially under-reported for a number of 

reasons. Crash databases typically exclude accidents that have less than $1,000 in property 

damage, not all drivers report collisions with animals, and not all law enforcement, natural 

resource, or transportation agencies have the resources to collect detailed information on WVCs. 

Furthermore, many animals that are injured wander away from the road before they die and are 

never found. 

Using a combination of carcass count data, insurance industry information, police-reported 

crashes, and interviews with the public, this study estimates that there are between one and two 

million collisions between vehicles and large animals in the United States every year. Almost all 

animal-vehicle collisions (AVCs) resulted in no human injury (95.4 percent). Collisions with 

moose and other large animals can have a higher likelihood of resulting in harm to the vehicle 

occupant (figure ES5 and figure ES6). 
 5 

1.7% 0.5%

2.3%

95.4%

0.04%

None

Possible

Minor

Severe

Fatal

 

Figure ES5. Graph. Human injury from AVCs (primarily deer). 

12%

82%

6%

Deer

Moose

Other

 

Figure ES6. Graph. Animal species involved in fatal (to human) collisions, Maine. 

Is the Number of Accidents Increasing? 

National trends were studied in a review of several sources of crash data. Figure ES7 and figure 

ES8 illustrate that from 1990 to 2004, the number of all reported motor vehicle crashes has been 

holding relatively steady at slightly above six million per year. By comparison, the number of 

reported AVCs (includes wildlife and domestic animals) has increased by approximately 

50 percent over the same period, from less than 200,000 per year in 1990 to a high of 

approximately 300,000 per year in 2004. Looking at the data another way, AVCs now represent 

approximately 5 percent (or 1 in 20) of all reported motor vehicle collisions. 
 6 

Figure ES7. Graph. Total vehicle crashes. 

Figure ES8. Graph. Total AVCs (including wildlife and domestic animals). 

The increase in WVCs appears to be associated with an increase in vehicle miles traveled (VMT) 

and an increase in deer population sizes in most regions in the United States. The occurrence of 

WVCs, however, is associated with many more factors, as reflected by their characteristics, 

which include: 

• More than 98 percent of WVCs are single-vehicle crashes. 

• 89 percent of WVCs occur on two-lane roads. 

• WVCs occur more frequently on low-volume roads. 

• Compared to all motor vehicle collisions, WVCs occur more frequently on straight roads 

with dry road surfaces. # AVCs 
 7 

• WVCs occur more frequently in the early morning (5–9 a.m.) and evening 

(4 p.m.–12 a.m.), when deer are more active and traffic volume is relatively high. 

• WVCs occur more frequently in spring and especially in fall, when animals move around 

more due to migration, mating, or hunting seasons. 

• The vast majority (as high as 90 percent in some states) of reported WVCs involve deer. 

• White-tailed deer-vehicle collisions are associated with diverse landscapes with abundant 

edge habitat (transitions from cover to more open habitat) and riparian habitat. 

WHAT ARE THE CONSEQUENCES? THE COSTS AND IMPACTS TO DRIVERS AND 

ANIMALS 

WVCs can have a broad range of consequences for both motorists and animals. Though human 

injuries and fatalities resulting from WVCs are relatively rare, they do occur and are a serious 

consequence. More common results are vehicle damage, secondary motor vehicle crashes, 

emotional trauma, and less direct impacts such as travel delays. WVCs can also require the 

assistance of law enforcement personnel, emergency services, and road maintenance crews for 

potential repairs and carcass removal. For animals, WVCs present an immediate danger to their 

individual survival, and certain threatened and endangered species are faced with a further 

reduction in their population survival probability. 

Impacts on Travelers 

Safety Risk 

Collisions with large animals pose a safety risk to humans as well as wildlife (figure ES9). Based 

on research from various states, roughly 4–10 percent of reported WVCs involving large animals 

result in injuries to drivers and their passengers. While this may not appear to be a large 

percentage, this translates into approximately 26,000 injuries per year that are attributable to 

these accidents. 
 8 

Figure ES9. Photo. A mule deer is hit by a vehicle in Big Bend National Park, TX 

(copyright: Marcel Huijser). 

Similarly, only a very small proportion of crashes with large animals result in human fatalities. 

Nonetheless, an estimated 200 people die from WVCs in the United States every year. From 

2001 to 2005, an average of 38,493 fatal crashes occurred.(2) Hence WVCs represent roughly 

0.5 percent of fatal crashes. 

Direct Monetary Impacts 

For vehicle owners, the most common direct cost incurred from a WVC is damage to their 

vehicle. Most research indicates that more than 90 percent of collisions with deer result in 

damage to the driver’s car or truck. Nearly 100 percent of collisions with larger animals—such 

as elk or moose—end with substantial vehicle damage. 

Due to the size and weight of the animals, damage to the vehicle can be costly. Based on 

numerous studies, the average cost of repairing a vehicle after colliding with a deer was 

estimated at $1,840. For collisions with elk and moose, the averages increase to $3,000 and 

$4,000, respectively. 

Drivers may incur other direct costs if they must have their vehicle towed after the accident. If an 

injury occurs, drivers and passengers may face expenses from medical care and possibly lost 

wages from missed work. 
 9 

WVCs have financial implications for public agencies as well. Law enforcement agencies face 

direct costs of investigation and traffic control following a collision. Transportation agencies 

typically are responsible for carcass removal and disposal costs and infrastructure repair costs, if 

necessary. Public agencies may incur some financial losses based on the monetary value of the 

animal itself, value associated with its hunting or license fees or recreational attraction for 

wildlife viewing. 

The best estimate of the total annual cost associated with WVCs, based on available data, is 

calculated to be $8,388,000,000. Collisions with deer constitute the single largest collision 

category involving human and vehicle costs. The average costs from a collision with a deer 

include the following: 

• $1,840 in vehicle repair costs. 

• $2,702 in medical costs. 

• $125 in towing and law enforcement services. 

• $2,000 for the monetary value of the animal. 

• $50 for carcass removal and disposal. 

• Costs can increase substantially if a car collides with a larger animal (such as an elk or 

moose). 

Indirect Impacts on Travelers 

WVCs can have other impacts on travelers that are more difficult to quantify in fiscal terms. 

Accidents involving large animals can lead to travel delays or secondary accidents for 

subsequent motorists if the vehicle or animal lies in the right of way. Some drivers also 

experience emotional trauma as a result of the danger they experienced and the killing of a large 

animal. 

Impacts on Wildlife 

WVCs are a serious safety risk for animals. In most cases, an animal that has been hit by a 

vehicle dies immediately or shortly after a collision. Clearly, these deaths affect the immediate 

survival of many individual animals. However, they also represent a serious conservation issue. 

For some species, the long-term survival of a local or regional population may be threatened, 

especially in combination with other factors such as habitat loss due to agriculture and 

urbanization. 

This study identified 21 federally listed threatened or endangered animal species in the United 

States for which road mortality is among the major threats to the survival of the species. These 

species include birds such as the Hawaiian goose (figure ES10), reptiles such as the desert 

tortoise (figure ES11), mammals such as the San Joaquin kit fox (figure ES12), and amphibians 

such as the California tiger salamander.
 10 

Figure ES10. Photo. Hawaiian goose warning sign 

(copyright: Haleakala National Park, National Park Service). 

Figure ES11. Photo. Desert tortoise (copyright: Marcel Huijser). 
 11 

Figure ES12. Photo. San Joaquin kit fox (copyright: Brian L. Cypher, California State 

University, Stanislaus, Endangered Species Recovery Program). 

THREATENED AND ENDANGERED SPECIES 

This study identified 21 federally listed threatened or endangered species in the 

United States for which road mortality is among the major threats to the survival of 

the species: 

Mammals 

Lower Keys marsh rabbit, Key deer, bighorn sheep (peninsular California), San 

Joaquin kit fox, Canada lynx, ocelot, Florida panther, red wolf 

Reptiles 

American crocodile, desert tortoise, gopher tortoise, Alabama red-bellied turtle, bog 

turtle, copperbelly water snake, eastern indigo snake 

Amphibians 

California tiger salamander, flatwoods salamander, Houston toad 

Birds 

Audubon’s crested caracara, Hawaiian goose, Florida scrub jay 

Note that other factors such as habitat loss due to agriculture and urbanization also 

impact these species and that a substantial reduction in WVCs may not automatically 

result in viable populations. 
 12 

CAN THE NUMBER OF COLLISIONS BE REDUCED? METHODS FOR 

PREVENTING COLLISIONS 

For this study, 34 different techniques aimed at reducing the number of WVCs were identified 

and reviewed. This section presents only some examples of the mitigation measures aimed at 

reducing WVCs; other measures are described and evaluated in the main text of the report. The 

measures are grouped into four major categories: efforts to change or influence the behavior of 

wildlife, efforts to reduce wildlife population size, efforts to change or influence a driver’s 

behavior, and planning and design approaches. It should be noted that the Federal Highway 

Administration (FHWA) is not recommending these measures by including them in this report. 

Influencing Wildlife Behavior 

WVCs can be reduced by influencing the behavior of animals. These efforts either attempt to 

deter animals from approaching the roadway or direct the animals toward a safer location to 

cross the road. 

Wildlife fences that separate animals from the roadway have a successful record of reducing 

WVCs and are now used extensively. Wildlife fences typically consist of wire mesh fence 

material that is 2 to 2.5 m (6.5 to 8 ft) tall, running parallel to the roadway (figure ES13). 

Numerous studies in the last 20 years have demonstrated that wildlife fencing, with or without 

wildlife crossing structures, can reduce collisions with deer and other large animals by 

87 percent on average (80–99 percent). 

Figure ES13. Photo. Wildlife fencing along Interstate 90 

near Bozeman, MT (copyright: Marcel Huijser). 
 13 

While correctly installed wildlife fencing is highly effective in reducing collisions, it must be 

carefully applied to avoid unintentional effects such as creating an absolute barrier that keeps 

animals from accessing habitat on the other side of the road. In addition, animals are more likely 

to break through the wildlife fencing if safe crossing opportunities are not provided or if these 

opportunities are too few, too small, or too far apart. Therefore wildlife fencing is usually 

combined with safe crossing opportunities, such as wildlife underpasses (figure ES14 and figure 

ES15) and overpasses. In addition, wildlife jump-outs are usually integrated with wildlife 

fencing. These features allow animals that do manage to cross the fence to escape from the 

fenced road and right of way. 

Figure ES14. Photo. Wildlife underpass in southern Florida that allows for ecosystem 

process (hydrology) as well as wildlife use, including the Florida panther 

(copyright: Marcel Huijser). 

Wildlife underpasses and overpasses provide safe road crossing opportunities for a wide array of 

species, allowing them to continue to move across the landscape. These structures are typically 

used in combination with wildlife fences that keep the animals from entering the roadway and 

that funnel the animals toward the overpasses and underpasses. In some cases wildlife 

underpasses and overpasses have no or very limited wildlife fencing, making them the primary 

measure to reduce WVCs on short road sections. The location, type, and dimensions of wildlife 

crossing structures must be carefully planned with regard to the species and surrounding 

landscape. For example, grizzly bears, deer, and elk tend to use wildlife overpasses to a greater 

extent than wildlife underpasses, while black bears and mountain lions use underpasses more 

frequently than overpasses. In addition, different species use different habitats, influencing their 

movements and where they want to cross the road. Other factors that should be considered are 

the vegetation in the direct vicinity of the crossing structure, co-use by humans, and the time it 
 14 

takes for animals to learn the location of the structures and to learn that they are safe to use. 

Although wildlife overpasses are more common in Europe than North America, some of the best 

studied examples are located in Banff National Park in Canada, and multiple large overpasses are 

planned in the United States. 

Figure ES15. Photo. Large culvert with vegetative cover and fencing on Highway 1 in 

Canada (copyright: Tony Clevenger). 

Large boulders parallel to the road can be an alternative to wildlife fencing, especially if 

landscape aesthetics are a concern. Preliminary data suggest that hoofed animals are reluctant to 

walk across large boulders. Smaller rocks have also been used at fence ends to discourage hoofed 

animals from wandering in between the fences. 

Long tunnels (or landscape bridges) are tunnels that are at least several hundreds or thousands of 

yards long (figure ES16). Long bridges (or elevated road sections) are bridges that span a similar 

distance. Long tunnels and bridges are primarily constructed because of the nature of the terrain 

(e.g., through a mountain, across a floodplain), but in some cases they are constructed to avoid 

areas that are ecologically very sensitive and where no alternatives are available. If the nature of 

the terrain permits, animals can move freely over long tunnels or under long bridges, and 

because the animals are physically separated from traffic, WVCs are eliminated. However, long 

tunnels or bridges are rarely specifically designed to reduce WVCs. 
 15 

Figure ES16. Photo. Long bridge on Arizona Highway 260 constructed in such a way as to 

minimize the impact to soil and vegetation (copyright: Marcel Huijser). 

Reducing Wildlife Population Size 

Wildlife culling involves a substantial reduction in the population size of a particular species in a 

certain area. When used, this measure is typically applied to deer. Culling is sometimes done by 

recreational hunters through increased deer quotas and sometimes it is accomplished by hiring 

professionals. The elimination of does (females) is more effective than the killing of bucks 

(males) because there is a greater impact on the reproductive potential of a population. Culling 

efforts are more likely to result in a substantial reduction in deer population size if the herd size 

is relatively small to begin with and if it is a closed population that does not allow influx of 

animals from nearby places. Data on the effect of culling on deer-vehicle collisions (DVCs) are 

scarce. One field test in Minnesota showed that a deer population reduction program reduced 

winter deer densities by 46 percent and DVCs by 30 percent. Sharpshooting by professionals 

using bait was deemed to be the most effective and adaptable culling method in an urban setting, 

as opposed to controlled hunts in large parks and refuges or opportunistic sharpshooting by 

professionals. The effort will have to be repeated periodically, as the deer population will return 

to the same levels if the habitat conditions remain similar; culling is not a one-time-only 

measure. In addition, the effort involved for population size reduction programs increases 

disproportionately with higher population size reduction goals, and substantial reductions (for 

example ≥ 50 percent) may be hard to obtain, perhaps capping the potential reduction in DVCs at 

50 percent. Finally, wildlife culling can meet with strong public opposition. 

Modifying Driver Behavior 

Efforts aimed at helping motorists avoid collisions depend on providing the driver with 

information. The driver may then take action, for example, by choosing when or where to drive, 

remaining alert, or lowering vehicle speed (figure ES17). 
 16 

Figure ES17. Photo. Permanently flashing Florida black bear warning signs in the Ocala 

National Forest, FL (copyright: Marcel Huijser). 

Animal detection systems use sensors to detect large animals that approach the road. Once a 

large animal is detected, warning signals are activated to inform drivers that a large animal may 

be on or near the road at that time. Such systems have been installed at over 30 locations in 

North America and Europe. Limited data exist on the effectiveness of animal detection systems, 

but a Swiss study showed that collisions with large hoofed animals were reduced by 82 percent 

on average for seven different locations. While these data are encouraging, animal detection 

systems should still be regarded as experimental, as more data on their effectiveness is needed. 

Animal detection systems applied over long road sections do not restrict animal movements. 

Animal detection systems may also be applied at gaps in a wildlife fence or at fence ends. This 

mitigation measure still allows large animals to be on the roadway, and the posts, sensors, and 

other equipment associated with the system may pose a safety hazard of their own. 

Public information and education programs aim to increase motorists’ awareness of the impacts, 

causes, and high risk locations of WVCs. These campaigns may also offer advice on how to 

avoid crashes with animals or how to reduce their severity. Dissemination of this information is 

often targeted to drivers at specific high risk locations or during seasons of high wildlife 

movement. Little research has been conducted to conclude whether these efforts are effective on 

their own; therefore, they are generally integrated with other mitigation measures. 
 17 

Planning and Design Methods 

Integration of transportation planning and wildlife management on a regional or statewide level 

can help to reduce WVCs. These efforts do not generally reduce WVCs in a direct or easily 

quantifiable manner. However, by working together, planners from transportation, resource, 

park, and other agencies find opportunities to share information and make planning decisions 

that help prevent or reduce WVCs. Examples include: 

• Avoidance of key habitat. Some states have chosen to avoid impacts in the most sensitive 

areas, for example by choosing an alternative route for a new road. This may avoid 

increased WVCs. 

• Identification and prioritization of WVC problem areas. Some transportation agencies use 

roadkill data, animal movement data, aerial photos, and mapping tools to identify habitat 

linkage zones (areas of high animal movement) and WVC locations. With this 

information, transportation agencies can focus limited resources on mitigating high 

priority locations. Having such information available also allows for the early integration 

of these WVC reduction measures with road building or road upgrading plans. This 

increases the probability that mitigation measures will be implemented and that WVCs 

will be reduced. 

• Data collection. Planners need good data regarding the magnitude and trends of WVCs so 

that they can identify and prioritize areas that may require mitigation. In addition, these 

data help in evaluating the effectiveness of potential mitigation measures. Some states 

have established data standards; others are developing methods to make it easier to 

collect detailed and accurate information (figure ES18). Having good data increases the 

probability that mitigation measures will be implemented and that WVCs will be 

reduced. 

• Consideration of geometric and roadside design features can reduce WVCs: 

• Steeper fill slopes may not allow drivers to see deer approaching the roadway until the 

animals leap over the guardrail. If a steeper side slope is unavoidable, a landing area may 

allow drivers to see animals before they jump over the guardrail. 

o At locations where the roadway crosses drainages, known migration corridors, or 

known animal habitat, avoid curves, steep side slopes, and narrow clear zones, 

which may make animals visible to drivers. 

o At locations where culverts or bridges are installed, culverts and bridges can 

possibly be widened to include opportunities for animals to cross under the road. 

o Drainage features can be designed to minimize wildlife attraction and influence 

wildlife movement. Avoid creating pooled water in the right of way which 

increases vegetation and attracts wildlife. Some wildlife will avoid crossing riprap (large boulders). If rip-rap funnels animals to an undesirable crossing location, 

consider filling gaps in the rip-rap with sand and gravel (which may make it more 
 18 

conducive to animals crossing) or extend the rip-rap to a more suitable crossing 

location. 

o When considering seeding mixes for the roadside, consider unpalatable species. 

Also consider plants that do not grow so tall as to visually obscure animals 

approaching the roadway. 

o Concrete median barriers may cause wildlife to pause at the barrier or turn 

around, increasing their time in the roadway. 

Which Methods Are Most Effective? 

There is no single, low-cost solution for WVCs that can or should be applied everywhere. A 

successful mitigation strategy requires a detailed, location-specific analysis of the problem and 

often involves a combination of different types of mitigation measures. Nonetheless, wildlife 

fences, with or without wildlife crossing structures, animal detection systems, and long tunnels 

or bridges, reduce or may reduce WVCs substantially (≥ 80 percent). Of these mitigation 

measures, wildlife fences, with or without wildlife crossing structures and animal detection 

systems, are among the most cost-effective measures. 

ARE WE MAKING PROGRESS? CHALLENGES FACED BY TRANSPORTATION 

AGENCIES 

With several successful WVC mitigation methods available, why hasn’t more progress been 

made toward reducing the number of WVCs? This study identified several challenges that 

currently prevent a systematic, nationwide approach to WVC reduction. 

Gaps in Knowledge, Insufficient Information, and Lack of Data 

There are no standards or guidelines for the collection of data on WVCs. Data are collected 

inconsistently and often haphazardly, and methods vary between states and agencies. Some 

transportation agencies do not collect this type of data at all. Without reliable, consistent data, it 

is difficult to identify road sections where mitigation methods may be required, to select an 

appropriate mitigation measure, or to evaluate whether that effort is making a difference. Future 

analyses should also include additional statistical methods to analyze the data. 
 19 

Figure ES18. Photo. Roadkill observation collection system (ROCS), a GPS-enabled PDA 

for animal carcass data collection (copyright: Amanda Hardy, WTI). 

Research and Evaluation of Mitigation Measures 

While several mitigation methods show promise, transportation agencies need data that show the 

effectiveness of different types of mitigation measures to justify their deployment. Additional 

research and field demonstration of WVC reduction techniques (figure ES19) help advance the 

state of the practice as results depend on the type of problem, the species involved, and local 

circumstances. Long-term monitoring of the effectiveness of the mitigation measures is needed, 

as WVC numbers are highly variable in nature. In addition, wildlife use of crossing structures 

tends to increase over time, as animals need time to learn their locations and learn that they are 

safe to use. 

Training 

While many transportation agencies are interested in reducing WVCs, their staff may not have 

the knowledge or experience to select effective methods. DOT planners and design engineers 

need training and guidance materials before they can begin to implement WVC reduction plans. 
 20 

Figure ES19. Photo. Animal detection system along U.S. Highway 191 in Yellowstone 

National Park, MT (copyright: Marcel Huijser). 

WHERE DO WE GO FROM HERE? OPPORTUNITIES AND NEXT STEPS 

This study has provided an opportunity to document the central issues related to WVCs on 

America’s highways: the magnitude and trend of the problem, the dangers posed to both drivers 

and animals, successful and promising methods for reducing the number of collisions, and 

challenges that lie ahead. 

More importantly, the findings of this study can help policymakers make informed choices 

regarding future efforts to reduce WVCs. Policymakers who wish to take the lead in advancing 

effective WVC safety measures can begin by considering the following recommendations: 

• Incorporate WVC reduction into the early stages of planning and design for 

transportation projects. 

• Develop and implement standards and guidelines for the collection of data on and 

reporting of WVCs. 

• Develop and implement guidelines for the evaluation of mitigation measures. 

• Evaluate the effectiveness of mitigation measures that have been recommended for 

further research. 

• Conduct additional analysis of the data and conduct research to further develop and 

improve existing mitigation measures (figure ES20). 
 21 

Figure ES20. Photo. Animal detection test-bed used to test the reliability of multiple animal 

detection systems, Lewistown, MT (copyright: Marcel Huijser, WTI). 

• Implement (or install) proven mitigation measures where appropriate. 

• Develop and apply wildlife population viability models to assist with locating and 

designing mitigation measures. 

• Conduct technology transfer to state DOTs, resource agencies, and other transportation 

professionals regarding the findings of this study. A handbook and training course on 

WVC reduction techniques will be developed by 2008, which will help in making the 

information available to practitioners. 

 23 

CHAPTER 1. INTRODUCTION 

In the recently enacted transportation bill, the Safe, Accountable, Flexible, and Efficient 

Transportation Equity Act: A Legacy for Users (SAFETEA-LU Public Law 109-59), the U.S. 

Congress directed the Secretary of Transportation to conduct a national WVC study. In response, 

FHWA sponsored a WVC study aimed at reviewing methods to reduce collisions between motor 

vehicles and wildlife. The Study will advance the understanding of the causes and impacts of 

WVCs and identify solutions to this growing safety problem. This Study is a unique opportunity 

to synthesize current knowledge from the United States, Canada, Europe, and elsewhere to 

promote the expertise, coordination, and effectiveness of transportation agencies in addressing 

WVCs and, ultimately, reduce WVCs on U.S. roadways. 

Approximately 300,000 reported collisions between cars and large animals (i.e., animals capable 

of causing substantial property damage upon impact) occur every year in the United States, and 

the number is steadily increasing. Including unreported collisions, the total number is more likely 

between one and two million WVCs annually. The increasing trend is expected to continue as 

both traffic volumes and deer populations continue to increase nationwide. Of the reported 

crashes, approximately 26,000 resulted in human injuries and 200 resulted in human fatalities per 

year. This study identified 21 federally listed threatened or endangered animal species in the 

United States for which road mortality was documented as a major threat to their survival. 

The remainder of this report provides information relating to WVCs and associated mitigation 

measures based on the literature review. The primary sections are listed below: 

• Causes and Characteristics of WVCs provides an overview of what is known about 

WVCs. It includes those issues documented in the literature and provides an analysis of 

national crash datasets. This section is primarily focused on large animals. 

• Economic Impacts of Wildlife-Vehicle Collisions summarizes the known costs of 

WVCs nationally. This section is also primarily focused on large animals. 

• Impacts to Wildlife provides a list and discussion of endangered species that are known 

to be impacted by WVCs directly. This report does not include issues relating to habitat 

loss, habitat fragmentation, or other impacts of roadways on wildlife. 

• A broad range of Mitigation Methods are discussed in several sections (organized into 

major categories). For each mitigation method, the report provides, if available, (1) a 

general description, (2) case studies (with contacts), (3) benefits and drawbacks, (4) costs, 

and (5) design guidelines. The major mitigation categories considered are as follows: 

o Methods that aim to influence driver behavior. 

o Methods that aim to influence animal behavior with no or minimal structures 

on/over the road or in the right of way. 

o Methods that seek to reduce the wildlife population size. 
 24 

o Methods that aim to physically separate animals from the roadway. 

o Planning considerations. 

• Results are summarized for an Evaluation of Mitigation Methods by a Technical 

Working Group of national experts. 

• Gaps in Current Knowledge provides a summary of topics related to WVCs that require 

further research and investigation. 

• Cost-Benefit Analyses provides an overview of the costs and benefits of the different 

mitigations. 

• A brief Conclusion ends the report. 

This document reports on Tasks 1–3 of the study, which include a literature review and technical 

working group meeting. Other elements of this project, which will be covered in later separate 

deliverables, include the following: 

• Best Management Practices Manual. 

• Training Course. 

In this document three terms are used to describe collisions with animals. Animal-vehicle 

collisions (AVCs) refer to collisions with wild and domestic animals in cases where domestic 

animals could not be separated from the dataset. WVCs include all species of wild animals. 

Deer-vehicle collisions (DVCs) include WVCs that involve only deer (Odocoileus sp.). The 

reason a separate term is used for deer and no other specific type of animal is that deer account 

for a majority of WVCs when data are available. When information is specific to one type of 

animal other than deer, no abbreviation is used (e.g., moose-vehicle collision). 
25 

CHAPTER 2. CAUSES AND CHARACTERISTICS OF WILDLIFE-VEHICLE 

COLLISIONS 

The primary method of investigating the causes and characteristics associated with WVCs is to 

analyze data on previous collisions. This chapter provides a summary of current knowledge 

about WVCs, based on information from the literature and an update from national crash 

databases. After discussing data sources and evaluation methods, this chapter investigates the 

following characteristics of WVCs: 

• Total magnitude. 

• Growth rate. 

• Temporal distribution by: 

o Time of day. 

o Time of year. 

• Severity of human injuries and fatalities. 

• Roadway facility type. 

• Traffic density and speed. 

• Weather conditions. 

• Animal species. 

• Landscape adjacent to roads. 

• Number of vehicles involved. 

• Deer population density. 

• Driver characteristics. 

DATA SOURCES 

Numbers and factors related to WVCs have been reported extensively in the literature. Possibly 

the most commonly quoted statistic is that there are over one million WVCs with large animals 

annually in the United States. This number originally comes from a survey of states completed 

by Romin and Bissonette.(3) States responded to this survey with a mix of crash record numbers, 

carcass counts, and estimates. Approximately 500,000 DVCs were reported by 35 states. 

Conover and others estimated that DVCs are underestimated by at least 50 percent, so most 

researchers increase this number to one million or more to include the missing states and 

unreported crashes.(4) 

There are three common sources of data for WVCs: carcass counts, the insurance industry, and 

police-reported crashes. The first source, carcass counts, includes counts of dead animals on the 

side of the roadway that likely died from collisions with a vehicle. Sometimes these data include 

more detail than just the species (e.g., sex, age, size, etc.). Unlike the two other sources discussed 
26 

below, carcass counts are not always focused on safety and can include smaller animals since 

conservation concerns are also a reason to collect carcass data. This source of data may be 

sufficient for corridor or regional studies, but the lack of consistency in reporting methods limits 

evaluation on a statewide or national level. However, it is often thought that carcass counts are 

the most comprehensive data available since the following two sources tend to underreport the 

total number of WVCs. 

Another source of information on WVCs is data from the insurance industry, which is based on 

reported claims. Claims typically relate to major damage, and major damage is typically 

associated with relatively large animals (e.g., deer size and up). State Farm Insurance estimated 

the number of claims for collisions with deer, elk, and moose and then estimated the total 

number nationally based on the company’s proportion of market share of insurance policies.(5)

This estimate is questionable. The number may underreport total collisions, since it only includes 

vehicles with comprehensive insurance; accidents with uninsured vehicles are not reported to the 

insurance industry. On the other hand, it could be overestimating crashes, since people may be 

likely to say they hit a deer when they actually hit something else in an attempt to keep their 

insurance rates low. As shown in figure 1, there are approximately one million WVC insurance 

claims annually (years are shown as fiscal years, July 1–June 30). This source of data typically 

does not contain detailed information about each crash. 

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

FY02-03 FY03-04 FY04-05 FY05-06

Fiscal Year 

Annual WVCs

Figure 1. Graph. Annual WVCs estimated by insurance industry.(5) 

The third source of WVC information is police reports of total crashes of all types (including 

WVCs). These reports are more effective for analyzing data nationally, because there is more 

consistency in their collection. The transportation industry expends considerable effort collecting 

and cleaning up these data for accurate analysis. However, this data set also has its limitations. 

These data only include crashes on public roads. In addition, these reports only include data for 

accidents that incurred a certain level of damage to the vehicle (each state has its own reporting 

threshold). Finally, the data may not include information on animal species, because these 

reports are focused on safety in general and are not specific to WVCs. In fact, the crashes may 
27 

only be categorized as AVCs (not separating domestic and wild animals). Three national police 

report-based datasets were used in this review as described below. 

NATIONAL CRASH DATABASES 

Each state maintains its own database of crash records with different reporting thresholds, 

different variables describing the contributing factors, and different database structures. WVCs 

were analyzed from three sources: 

• Fatal Accident Reporting System (FARS) includes all crashes nationally that involve a 

human fatality. The data from this system are likely the most consistent nationally since 

more detail and effort goes into reporting a fatal crash. However, the dataset is small with 

typically fewer than 200 AVC fatal crashes annually. From 2001 to 2005, an average of 

38,493 fatal crashes occurred.(2) Hence AVCs represent roughly 0.5 percent of fatal 

crashes. 

• The Highway Safety Information System (HSIS) includes all reported crashes from 

Washington, California, Illinois, Maine, Michigan, Minnesota, North Carolina, Ohio, and 

Utah. This is a useful source of data since some of these states report more detail on the 

species of animal involved in a crash. Although it contains all crashes reported, it is only 

for the selected states. 

• The General Estimates System (GES) is a true national sample. A small random sample 

of police accident reports is collected from each sampling unit. A sampling unit contains 

one or more police jurisdictions. The values from these police reports are aggregated up 

to determine national estimates. Although the collection methods are rigorous to ensure 

randomness, this is still only a sample of all crashes, so these are estimates of national 

values, not true national values. 

Throughout the rest of this chapter, numbers are reported from each of these three datasets. 

General issues and methods for analyzing these datasets are discussed here. It should be noted 

that national figures are analytically attractive because there is a much larger dataset, but they 

may mask significant differences in WVCs between local areas. 

Fatal Accident Reporting System 

Fatal Accident Reporting System (FARS) data include those crashes where at least one person 

died within 30 days of the collision from collision-related injury. Data were collected from 2001 

to 2005. AVCs were identified when a crash’s “first harmful event” was an animal. Note that for 

these events, the “most harmful event” was not always an animal. Data were downloaded from 

the FARS Web site (http://www-fars.nhtsa.dot.gov/)(accessed November 27, 2006). The first 

harmful event is the first event during a crash that causes injury or property damage. The most 

harmful event causes the most damage and is not always the same as the first harmful event. 

Highway Safety Information System 

HSIS data contain police-reported accidents for Washington, California, Illinois, Maine, 

Michigan, Minnesota, North Carolina, Ohio, and Utah. HSIS was developed and is maintained 
28 

by FHWA. Information can be found at http://www.hsisinfo.org (accessed January 24, 2007). 

This database includes all police-reported crashes for these states; therefore, it has a larger 

sample than the random sample in the GES dataset, but it does not contain data beyond these 

states. A strength of this dataset is that some of the detail collected by individual states is 

maintained. For example, Maine divides its AVCs into deer, bear, moose, and other. 

HSIS states have different data availability. The most recent 5 years of data from each state were 

analyzed (table 1). Also shown in table 1 are the reporting thresholds for each state. 

Table 1. Summary of HSIS data characteristics from different states.

State Years Thresholds Animal Categories 

California 1998–2002 

Differ by municipality: 

from $500 to $1,000 or 

injury only. 

Deer, livestock, other 

animal (except in 2001) 

Illinois 1999–2003 $500 or injury Deer, other animal 

Maine 2000–2004 $1,000 or injury 

Deer, bear, moose, other 

animal 

Minnesota 2000–2004 $1,000 or injury 

Deer, other animal (except 

2000–2002) 

Michigan 1993–1997 $400 or injury Animal only 

North Carolina 2000–2004 $1,000 or injury Animal only 

Utah 1996–2000 $750 or injury Wild or domestic animal 

Washington 2000–2004 $750 or injury 

Large domestic, small 

domestic, wild animal 

The manner in which animals are categorized also varies between states (table 1). Some states 

simply have a single general category of “animal” for all AVCs. One category for all animals is 

similar to the GES and FARS animal categorization, which can include domestic animals. When 

reporting on HSIS data as a whole, domestic animals were excluded (unless otherwise stated) for 

those states that differentiated. As such, HSIS results refer to WVCs, even though some of the 

states may include domestic animals within their animal classification. 

Crash data can sometimes be misleading when a clear and detailed explanation of the reported 

value is not provided. For example, from the same source of data one could state that there were 

100 crashes, or that 200 vehicles were involved in a crash (i.e., there were 100 crashes, each 

involving two vehicles). In this report, unless otherwise stated, crash numbers refer to number of 

crashes (not number of vehicles or people). When referencing the vehicle attribute, it refers to 

the vehicle that struck the animal (almost all crashes were single-vehicle crashes). When 

referencing the person attributes, it refers to the driver of that vehicle. 

To compare data from states with vastly different numbers of collisions (range = 176,793 to 

890,215), proportions of collisions were compared instead of raw numbers. Further, rather than 

using the sum of all collisions with certain characteristics (which would bias the total towards 

states with more collisions), the proportion of collisions within each state was summed and 

divided by the number of states. 
29 

General Estimates System 

GES is a stratified random sample. There are actually two strata. The first stratum is geographic. 

There are four regions (Northeast, Midwest, South, and West) that are further categorized into 

1,195 primary sampling units, each containing one or more police jurisdictions. Within these 

geographic areas, crash reports are sampled randomly. The second stratum is crash type (mostly 

in terms of severity). Crash types are divided into the following categories: 

• An occupant of a vehicle that was towed after the collision is killed or severely injured—

no medium or heavy trucks. 

• An occupant of a vehicle that was towed after the collision is injured—no medium or 

heavy trucks. 

• A passenger vehicle is towed after the collision (no fatalities or injuries)—no medium or 

heavy trucks. 

• A medium or heavy truck that resulted in a vehicle being towed or an injury report. 

• No vehicles were medium or heavy trucks, no vehicles were towed, and at least one 

person was injured. 

• No person was injured. 

The total number of crash reports (including those not sampled) is also known for each 

geographic and crash type sampling unit. Based on these sampling units, rates are determined 

such that each crash record is given a weight that is an estimate of the number of crashes it 

represents. When comparing across the crash strata mentioned above or considering total AVC 

numbers, the weighting factors were used. Since these weighting factors have not been published 

for 2005, these numbers represent 2000–2004 data. When considering variables within the AVC 

subsample (e.g., time-of-day distributions), straight proportions were used assuming there were 

random samples across nonsampling unit variables. For these numbers, 2001–2005 GES data 

without weights were used. The assumption regarding these proportions was not validated. 

Future analysis should include the most recent available data and include the weighting factors. 

GES data were downloaded from ftp://ftp.nhtsa.dot.gov/ges/ (accessed January 24, 2007). 

Total Vehicle Miles Traveled 

Researchers collected data on vehicle miles traveled (VMT) for each state. This information, 

coupled with the crash data described above, allowed for determination of crash rates. These 

rates are expressed as crashes per million VMT unless otherwise stated. These values allow 

researchers to compare crashes both geographically and over time to see if there is an increase in 

the exposure rate. VMT files were downloaded from the U.S. Department of Transportation, 

Bureau of Transportation Statistics (BTS) Web site at http://www.bts.gov/ (accessed January 24, 

2007). Annual national VMT were available through 2004. 
30 

EVALUATION METHODOLOGIES 

The goal of the remainder of this section is to summarize how WVCs (or AVCs when crash data 

could not be separated into domestic and wild animal) are unique from other crashes. It is 

difficult to normalize for all the secondary factors that may cause a certain distribution of WVCs 

for a given variable. The best method is to compare WVCs with non-WVCs. A proportional ttest or chi squared test can be completed to confirm a statistically significant difference. In the 

case of all reported differences, they were statistically significant. 

TOTAL MAGNITUDE 

Based on the HSIS data, Table 2 shows the WVCs for each of the eight states analyzed. The 

proportion of crashes that were WVCs in a given state ranged from 0.6 to 14.6 percent. The total 

number of WVCs in these eight states was 251,619 for a 5-year period (about 50,000 per year). 

Consider that these states comprise 16 percent of the total land area in the 50 United States and 

22 percent of the rural VMT in 2004. Considering the HSIS data represent about one-fifth of the 

United States, the national number of reported crashes is likely to be around five times the 

amount reported in the HSIS states (i.e., 50,000 per year). Extrapolating the HSIS data would 

yield an estimate of about 250,000 WVCs per year in the United States. 

GES estimates the national average of AVCs at 292,000 annually (2001–2004). This value 

represents 4.6 percent of all crashes annually. Based on FARS data, the total number of fatal 

crashes involving AVCs nationally averages 179 per year (2001–2005). From 2001 to 2005, an 

average of 38,493 fatal crashes occurred for all crash types.(2) Hence AVCs represent, on 

average, less than 0.5 percent of all fatal crashes. 

Table 2. Five-year crash totals for HSIS states. 

State WVCs All Collisions WVCs (%) 

California 5,580 890,215 0.63 

Illinois 29,038 664,263 4.37 

Maine 21,599 176,793 12.22 

Michigan 103,962 711,482 14.61 

Minnesota 21,621 415,118 5.21 

North Carolina 51,764 637,994 8.11 

Utah 12,449 240,381 5.18 

Washington 5,606 207,133 2.71 

Totals 251,619 3,943,379 6.38 

As mentioned previously, carcass counts have been extrapolated to a national estimate of over 

one million per year. Additionally, as shown previously in figure 1, the estimated number of 

insurance claims per year averages about one million. Table 3 summarizes the WVC counts from 

these various sources. 
31 

Table 3. Total annual magnitude of WVCs from various sources. 

Source Annual WVCs 

HSIS 250,000 

GES 292,000 

Insurance claims 1,000,000 

Carcass counts 1,000,000 

Marcoux conducted a survey in Michigan and found that of the people involved in a DVC, only 

52 percent reported it to their insurance company.(6) This finding implies that the estimated 

WVCs are underreported. The carcass counts are also not likely to include all WVCs, since they 

are extrapolated from a mix of reported collisions and carcass counts as well as from 35 to 

50 states. Considering all of these figures and the previously discussed potential underreporting, 

the authors recommend the following two numbers be used when discussing the magnitude of 

WVCs with large animals: 

• The total count of WVCs each year is between one and two million. 

• The number of WVCs that are reported to police and have enough property damage to 

warrant tracking in crash databases (e.g., greater than $400–1,000 depending on the state) 

totals 300,000 per year. 

Keep in mind that each of these numbers represent WVCs with large animals since they are 

based on reported crashes or carcasses. The total magnitude of WVCs with small animals is 

likely much larger. 

IS THE PROBLEM GROWING? 

Is the number of WVCs increasing or decreasing? A previous study of HSIS data found that 

WVCs increased 69 percent from 1985 to 1991.(7) 

Since GES data are likely the best source of national numbers, trends were examined using this 

data source, extending back to 1990. As shown in figure 2 and figure 3, the number of all crashes 

is holding relatively steady at slightly above six million, while the number of AVCs is 

increasing. This increase could be due to a number of different factors discussed later in this 

chapter such as an increase in deer population and changes in traffic volumes and speeds. 

To analyze WVC trends over time, three linear regression models were used, with the 

independent variable being the year and the dependent variable being either the total number of 

WVCs, the proportion of WVCs to total crashes, or the total crash rate. An important statistic is 

the t-statistic for the coefficient of the slope, which describes the relationship between the 

dependant and independent variables. If the t-statistic is greater than two, it can be confidently 

concluded (α = 0.05 or 95 percent confidence) that the slope is not zero (i.e., the rate of WVCs 

changing through time). Statistically a linear regression line on the total annual AVCs shows an 

increasing slope of 6,769 AVCs per year (t = 7.8, R-squared = 0.81). In addition, the proportion 

of AVCs to total crashes has a positive slope of 0.11 percent per year (t = 9.4, R-squared = 0.86). 
32 

Note that a higher R-squared value (which ranges from zero to one) indicates there is a linear 

relationship. An R-squared value of one results from a perfect linear relationship. 

 

Figure 2. Graph. Total vehicle crashes. 

Figure 3. Graph. Total AVCs (including wildlife and domestic animals). 

To ensure that the increase in WVCs over time was not due only to increases in the amount of 

travel (i.e., VMT), the crash rate was investigated. Figure 4 shows the crash rates each year 

determined by dividing GES annual numbers by VMT. The linear regression of crash rate over 

time has a positive slope of 0.00072 crashes per million VMT per year (t = 2.2, 

R-squared = 0.27). The linear relationship is weak as indicated by a low R-squared value. The 

t-statistic shows that the crash rate increase is statistically significant. 

Statistical analysis beyond linear regression models will be considered in future stages of this 

topic to further assess relationships. # AVCs 
33 

0.05

0.06

0.07

0.08

0.09

0.10

0.11

0.12

1985 1990 1995 2000 2005

Year

Collision Rate 

(per million VMT)

Figure 4. Graph. Annual crash rate for AVCs (GES and VMT data). 

TEMPORAL DISTRIBUTIONS 

For some species, there are clearly certain times of the day and times of the year when WVCs 

occur more frequently. For large mammals, numerous studies have shown that WVCs occur 

more frequently in the morning (5–8 a.m.), the evening (4 p.m.–12 a.m.), in the fall (October and 

November), and in the spring (May–June).(8,9,10) The peak in the spring is generally not as high as 

that in the fall. The daily peaks are typically explained by the fact that deer and other large 

animals are moving around dusk and dawn, which, combined with relatively high traffic volume 

in the early morning and late afternoon, results in a peak in collisions in the early morning and 

late afternoon and evening. The fall peak is typically explained as being related to mating season, 

migration, and hunting season, all of which cause animals to move around more.(11) The spring 

peak is explained by distribution of young and migration. 

Figure 5 shows the annual AVC distribution for the three reported crash datasets. The HSIS- and 

GES-based AVC distributions are very similar in magnitude and shape. The FARS data do not 

have the sharp peak in AVCs observed in November in the other two datasets. Note that for the 

HSIS data most of the states followed the same basic trend. Five of the eight states had 

substantial peaks in proportion of AVCs in November, while two states (California and 

Washington) had a larger peak in October and a smaller peak in November. Utah had the least 

overall difference in WVCs by time of year. All states except North Carolina and Utah had 

minor peaks in WVCs in spring, generally in June. 
34 

0

0.05

0.1

0.15

0.2

0.25

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Proportion of Collisions

FARS HSIS GES

Figure 5. Graph. Annual distribution of AVCs. 

Some HSIS states separated deer from other animals (WA, ME, IL, UT, and CA). For the “other 

animal” or domestic classifications the distribution is much more uniform throughout the year 

(figure 6). 

0

20

40

60

80

100

120

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Total Collisions (5-years)

Figure 6. Graph. Annual distribution for other/domestic animal-vehicle collisions in CA, 

WA, IL, ME, and UT (HSIS data). 

Maine was the only HSIS state to list specific wild species other than deer. For Maine, the annual 

distributions for bear- and moose-vehicle collisions (figure 7) do not have the major peak in 

November like deer (note AVCs reported in figure 5 are primarily deer). Bear-vehicle collisions 

are fairly uniform in the summer and nonexistent in the winter during their hibernation period. 
35 

0

100

200

300

400

500

600

700

800

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Total Moose (5-years)

0

5

10

15

20

25

Total Bear (5-years)

Moose Bear

Figure 7. Graph. Annual distributions for moose and bear collisions in Maine (HSIS data). 

Seasonal distributions appear to be somewhat dependent on specific geographic area. For 

example, in Teton County, Wyoming, WVCs were most frequent in summer months, especially 

in Grand Teton National Park, which has much higher traffic volumes in the summer.(12) These 

numbers contrast sharply with the more regional trends presented in figure 5. 

For time of day, the three data sources all show the expected peaks at early morning and evening 

(figure 8). Wildlife, especially deer, typically move around more at dusk and dawn. 

0

0.02

0.04

0.06

0.08

0.1

0.12

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour of Day

Proportion of Collisions

FARS GES HSIS

Figure 8. Graph. Time-of-day distribution. 
36 

SEVERITY 

Williams and Wells looked at 147 fatal WVCs from nine different regions and found that the 

most common types were (1) a motorcyclist striking an animal and falling off the vehicle 

followed by (2) a passenger vehicle striking an animal, going off the road, and striking a fixed 

object or overturning. Safety measures (i.e., helmets and seat belts) were not used in 

60–65 percent of the cases.(13) Jones also reported most fatal crashes involved motorcycles.(14)

This conclusion was confirmed by the FARS data. On average, 30 percent of the fatal crashes 

involving animals also involved motorcycles. Conn and others investigated 22,498 emergency 

room visits where a motor vehicle collision with a large animal was identified as the cause.(15) 

Of these, more than one-third (8,508) were people ages 15 to 24. 

In general, WVCs are less severe than other crashes. Compared to all crashes, the datasets show 

the proportion of crashes involving human injury is much less for WVCs. GES-based estimates 

of crash severity over 5 years are shown in figure 9 and figure 10 for AVCs and all crashes, 

respectively. Almost all AVCs resulted in no human injury (95.4 percent). This figure is 

consistent with the HSIS data that show 92.3 percent of crashes resulted in no human injury. 

There was some variability in severity values between the HSIS states, likely due to the different 

reporting thresholds. California showed only 87.4 percent of DVCs resulted in no injury. GES 

estimated fatal crashes at 608 in a 5-year period, compared to 895 in the FARS data. However, 

the upper confidence interval of the GES data is 1,956 fatal crashes. Note that for all crashes in 

this same 5-year period, FARS shows 192,463 fatal crashes. 

Figure 9. Graph. Severity distribution for AVCs (GES data). 

Often collisions with moose and other larger animals are thought to be more fatal to humans than 

collisions with deer. In Newfoundland, Joyce and Mahoney found that among moose-vehicle 

collisions, 0.6 percent were fatal crashes and 26 percent were injury crashes.(8) 

 

1.7% 0.5%

2.3%

95.4%

0.04%

None

Possible

Minor

Severe

Fatal
37 

Figure 10. Graph. Severity distribution for all crashes (GES data). 

From the HSIS data, domestic, livestock, and other animals had a slightly higher severity rate 

than WVCs, with 79.2 percent of crashes resulting in no human injury, which is lower than the 

92.3 percent value for all AVCs, but still higher than the 68.3 percent value for all crashes. 

Moose-vehicle collisions from the Maine HSIS data show a severity profile more similar to that 

of all collisions (figure 11). 

76.6%

7.2%

14.4%

1.4% 0.4%

None

Possible

Minor

Severe

Fatal

Figure 11. Graph. Severity distribution of moose-vehicle collisions in Maine (HSIS data). 

4.3%

9.4%

17.6%

68.3%

0.5%

None

Possible

Minor

Severe

Fatal

 
38 

FACILITY TYPE 

Most studies that look at the types of roadways where WVCs occur report that they are most 

common on rural two-lane roads.(7) However, these results should be used with caution since a 

large majority of highway miles are rural, two-lane roadways. 

For the GES records with number of lanes and facility types, 89.7 percent of AVCs occurred on 

two-lane roads. In comparison, 52 percent of all crashes occur on two-lane roads (figure 12). 

This is not to say that upgrading all two-lane roads would reduce WVCs. Reilly and Green found 

that the upgrade from two to four lanes in constructing Interstate 75 in Michigan initially resulted 

in a 500 percent increase in DVCs.(16) With time, the number of DVCs did steadily decrease. The 

initial increase could have been due to deer being unfamiliar with the new character of the 

roadway. 

0.0

0.2

0.4

0.6

0.8

1.0

1234567

Number of Lanes

Proportion of Collisions 

AVC ALL

Figure 12. Graph. AVCs by number of lanes (GES data). 

The majority of AVCs (91.7 percent) occurred on straight sections of roadways, compared to 

85.8 percent for all crashes, according to the GES data. However, these results vary by region. In 

the West Region, 74.8 percent of AVCs occurred on straight roads, compared to 82.7 percent of 

all collisions. 

TRAFFIC DENSITY AND SPEED 

The impact of traffic density and speed on WVCs is complex. Predictive models of DVCs for 

Kansas and also for Iowa positively correlated the number of DVCs per year per mile to the 

number of roadway lanes and/or traffic volume.(17,18) Using traffic flow theory, Langevelde and 

Jaarsma modeled the probability of successful wildlife road crossings based on relevant species, 
39 

road and traffic characteristics.(19) Traffic volume has a large effect on this probability, especially 

for slow-moving species.(19) 

Lower traffic volumes do not necessarily equate with fewer roadkills.(20) In fact, WVCs actually 

decrease when traffic volume increases to a high enough level that it is, in effect, a barrier (i.e., 

animals do not attempt to cross).(20,21,22) Several researchers have hypothesized a relationship 

similar to that shown in figure 13.(22,23,24) 

0

10

20

30

40

50

60

70

80

90

100

-- Increasing Traffic Volume -- >

Percent

 Successful

 Killed

 Repelled

Figure 13. Graph. Theoretical relationship between traffic volume, successful wildlife 

crossings, and road mortality (adapted from Seiler).(23) 

When analyzing the national crash data, AVCs are more likely to occur on low volume roads, as 

shown in figure 14. Almost one-half of WVCs in the HSIS states occurred on roadways with less 

than 5,000 average daily traffic (ADT). 
40 

0

0.1

0.2

0.3

0.4

0.5

0.6

1 to 5000 5001-

10,000

10,001-

15,000

15,001-

20,000

20,001-

25,000

25,001-

30,000

30,001-

35,000

>35,000

Average Daily Traffic (ADT)

Proportion of Collisions

AVC ALL

Figure 14. Graph. Crashes by ADT (HSIS data). 

There are numerous reports that attempt to correlate increasing speed to increasing WVCs. Such 

correlations can be misleading if the author is not clear on what is being compared and what the 

results can suggest. For example, figure 15 indicates that AVCs occur less frequently on lowspeed roadways. The initial conclusion could be that if the posted speed limit is lowered, the 

number of WVCs will decrease. However, the high number of AVCs on 88 km/h (55 mi/h) 

roadways (nearly 60 percent) is more likely a result of higher populations of wildlife on rural 

two-lane roadways with this design speed, rather than the 88 ki/h (55 mi/h) design speed in and 

of itself. 
41 

0

0.1

0.2

0.3

0.4

0.5

0.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Speed Limit (MPH)

Proportion of Collisions

AVC ALL

1 mi/h = 1.61 km/h 

Figure 15. Graph. Distribution by posted speed limit (GES data). 

Seiler found a similar trend with moose in Sweden. Moose-vehicle collisions peaked on roads 

with speed limits of 90 ki/h (56 mi/h) and declined at higher speeds.(25) Although an old study, 

Cottam found that collisions with birds also occurred more frequently on higher-speed 

roadways.(26) Cramer and Portier found that Florida panther WVCs increased with an increase in 

posted speed and traffic flow.(27) 

As shown in figure 16, the likelihood of fatal AVCs occurring on 88 ki/h (55 mi/h) roadways is 

lower than the likelihood of a non-AVC fatal crash on a roadway with the same speed limit. This 

relationship is opposite of the distribution for all AVC crashes discussed above. There are 

numerous possible explanations for this. One hypothesis is that motorcycles, which account for a 

large proportion of fatal AVC crashes, typically travel on lower-speed roadways. However, there 

has been insufficient research to verify what accounts for the difference in the distribution of 

speeds for fatal AVCs. 
42 

0

0.1

0.2

0.3

0.4

0.5

0.6

<=25 30-35 40-45 50-55 60-65 70-75

Speed Limit (MPH)

Proportion of Collisions

Fatal AVC ALL Fatal

1 mi/h = 1.61 km/h 

Figure 16. Graph. Distribution of fatal crashes by posted speed limit (FARS data). 

WEATHER 

WVCs are more likely to occur in dry weather, perhaps due to the fact that animals are less likely 

to move around during inclement weather. Carbaugh found there were fewer deer sightings 

during precipitation.(28) Ninety-five percent of fatal AVCs occurred during clear weather 

compared to 88 percent of all crashes. The proportion of accidents in clear weather is similar for 

GES (92 percent AVC and 85 percent all) and HSIS (92 percent of WVCs 83 percent of all). 

These results reinforce those of other research that show collisions with large animals typically 

occur on straight, dry roads.(29) 

ANIMAL SPECIES 

Data regarding animal species affected by WVCs vary considerably by state. Williams and Wells 

characterized 147 fatal WVCs from nine states in different regions of the United States between 

2000 and 2002.(13) Seventy-seven percent of these WVCs involved deer; other types of animals 

included cattle, horse, dog, bear, cat, and opossum. 

Of the eight HSIS states, six differentiated WVCs by some categorization scheme based on 

animal type (table 1). Illinois and Minnesota recorded DVCs and “other animal” collisions, 

although Minnesota only made this differentiation in 2003 and 2004. In both these states, deer 

made up more than 90 percent of the WVCs. California differentiated among deer, livestock, and 

other, except in 2001, when the species were not recorded. Using 1998–2000 and 2002 data only, 

deer represented 54 percent of AVCs (figure 17). Livestock are clearly not wild, but “other 

animal” could be wild or domestic. Non-animal represents WVC collisions in which an animal 

was involved but not struck (i.e., the driver swerves to avoid a deer and collides with a 

guardrail). 
43 

20.4%

14.9%

54.4%

10.3%

DEER

LIVESTOCK

OTHER ANIMAL

NON-ANIMAL

Figure 17. Graph. Animal species involved in collisions in California (HSIS data). 

In Maine, 81 percent of AVCs were attributable to deer and 15 percent attributable to moose 

(figure 18). Maine also recorded whether collisions occurred with bears and other animals. 

0.6% 3.1%

81.2%

15.1% DEER

MOOSE

BEAR

OTHER SPECIES

Figure 18. Graph. Animal species involved in collisions in Maine (HSIS data). 

Rather than differentiating by species, Utah and Washington divided their reported AVCs into 

wild and domestic species. Washington further divided domestic species into large (cattle, 

horses, etc.) and small (dog, cat, etc.) domestics (figure 19). Washington reported a 

preponderance of collisions with wild animals. In Utah, over the five years of study, 84 percent 

of all AVCs were due to collisions with wild animals rather than domestic animals, a slightly 

lower percent of wild animal collisions than reported in Washington. 
44 

91.7%

5.7% 2.6%

Large Domestic

Small Domestic

Wild

Figure 19. Graph. Animal species involved with collisions in Washington (HSIS data). 

LANDSCAPE ADJACENT TO ROADS 

Of all recorded accidents in the United States, the vast majority involve deer, especially whitetailed deer (Odocoileus virginianus). While deer and DVCs may be widespread, their occurrence 

is not randomly distributed across the landscape. White-tailed deer-vehicle collisions are 

typically associated with mixed landscapes that provide cover (forests, shrub land) as well as 

food (more open areas with grasses, herbs, crops, but also young trees).(30,31) A high 

heterogeneity and diversity of the landscape, proximity to cover, and the occurrence of edge 

habitat (transitions from cover to more open habitat), riparian habitat, and shrub land are strongly 

associated with the presence of white-tailed deer and white-tailed deer-vehicle collisions. (See 

references 30, 31, 32, 33, 34, 35, 36, 37, and 38.) 

Research results are mixed on the relationship between building density and WVCs, showing 

either a negative or positive association. In general there are fewer collisions when the density of 

buildings increases. (See references 25, 28, 31, 37, 39, and 40.) 

Mule deer (Odocoileus hemionus)-vehicle collisions are sometimes associated with seasonal 

migration corridors.(41,42,43) Seasonal migration of mule deer typically occurs in mountainous and 

heavy snowfall areas.(44) Furthermore, mule deer-vehicle collisions have been associated with 

large drainages and heavy cover.(45,46) Mule deer tend to avoid sites with human disturbance and 

deep snow.(47,48) Nonetheless, mule deer can adapt to an urban or suburban environment.(46,49) 

The relationship between slopes and DVCs is uncertain. Carbaugh found that deer favored steep 

declines and inclines and rarely used level areas.(28) By contrast, Malo and others found that 

lateral embankments, especially with guardrail, negatively correlated with DVCs.(39) Alexander 

and Waters found that slopes less than five degrees were optimal for wildlife movement, but that 

west to south facing slopes were also indicative of locations with wildlife movement.(50) Pellet 

found that on a section of Interstate 90 near Bozeman, MT, as the absolute mean slope increased 

up to 19.5 percent, ungulate vehicle collisions decreased; while further increases in slope led to 

an increase in collisions.(51) 
45 

NUMBER OF VEHICLES AND COLLISION TYPE 

Almost all WVCs are single-vehicle crashes (HSIS 98.5 percent, GES 99 percent). However, 

FARS data indicated a slightly lower percentage than the HSIS and GES data sources; only 

85.6 percent of fatal AVCs were single-vehicle crashes. The proportion of FARS AVCs is lower 

than the other datasets (which include nonfatal crashes); however, this value is still much higher 

than the proportion for all FARS crashes, of which 56.9 percent are single-vehicle crashes. From 

the FARS data it can be seen that aside from collisions with animals, the two highest collision 

types for AVCs were hitting another vehicle or overturning (figure 20), which reinforces the 

hypothesis that swerving to avoid a WVC may result in a higher-severity collision. 

17%

15%

9% 1%

58%

Animal

Overturned

Other Vehicle

Object

Other

Figure 20. Graph. Fatal AVCs by collision type (FARS data). 

DEER POPULATION DENSITY 

A relationship between deer population density and DVCs has been documented in several 

studies.(52,53,54) Over the last century deer population size has increased strongly in most regions 

in the United States.(55) For example, in Virginia the white-tailed deer population size increased 

from an estimated 25,000 animals in 1931 to 900,000 by the early 1990s.(55) In Wisconsin, prehunting population size estimates for white-tailed deer increased from 1,152,000 in 1993 to 

1,643,000 in 2004, but the estimated population size varied strongly between 1993 and 2004.(56)

In Iowa population size estimates for white-tailed deer increased from 500–700 in 1936 to 

360,000 in 2004.(54) In Wisconsin, the deer population estimates between 1993 and 2004 were 

poorly correlated with the number of DVCs.(56) In Iowa, deer population indices were closely 

correlated to the number of road-killed deer, both increasing by about a factor of 2.3 between 

1985 and 2004.(54) The increase has been especially strong since the 1960s.(55,57) The increase in 

deer abundance is correlated with the number of DVCs, at least across relatively large areas, but 

this correlation has not been analyzed at a national level.(53,54,58) 

The relationship between deer population density and the number of DVCs seems intuitive, but 

this is not necessarily the case.(59,60) A comprehensive review by Knapp, Putman and suggests 

that a reduction of the population size across a relatively wide area can be effective in reducing 

DVCs. (See references 52, 53, 54, 58, 61, and 62.) On the other hand, a reduction in population 
46 

over a large area does not necessarily result in a decrease in DVCs, and the reduction in 

population can be difficult to achieve and maintain, as is discussed further in chapter 7. Very few 

data exist on the effectiveness of population reduction programs in reducing WVCs, but one field 

test showed that a deer population reduction program in Minnesota reduced winter deer densities 

by 46 percent and DVCs by 30 percent.(52) 

DRIVER CHARACTERISTICS 

GES and HSIS data showed very little difference in the proportion of male drivers involved in 

WVCs versus all crashes. According to the FARS data, however, 81.8 percent of drivers 

involved in AVCs were male, compared to 74.8 percent in all crashes. 

The national rate of alcohol involvement in all collisions was 7.76 percent (GES crashes where 

alcohol involvement was known and recorded). Comparatively, only 0.4 percent of AVCs 

involved alcohol. This observation does not, of course, mean that being intoxicated decreases a 

driver’s chance of being involved in an AVC. This observation is likely due to some correlation 

between alcohol-related crashes and some other factor. 

Probably the most unexpected finding in comparing crash distributions of WVCs to all crashes 

was the difference in accident distribution by driver age (note that the same trend was found with 

FARS and GES data, but only HSIS data are shown in figure 21). The peak in the number of 

crashes (all types combined) for younger drivers (i.e., age 16–25), seen in figure 21, is typically 

explained by inexperience and more risky driving behavior. Specific attributes of younger 

drivers include less skill at detecting hazards, less ability to conduct some driving tasks 

automatically, being easily distracted, less skill in performing emergency maneuvers, less 

perception of risk, and overestimation of driving abilities.(63) For middle-age drivers, the chances 

of being involved in a crash are fairly constant across this age group but less than that of younger 

age groups (figure 21). As driver age increases, the number of drivers decreases, resulting in 

reduced exposure (in terms of VMT), explaining the reduction in the total number of crashes 

(figure 21). 

The unexpected finding is that, in contrast to the distribution for all crashes, WVC crashes have 

no pronounced spike for young drivers (figure 21). This suggests that the chance of being 

involved in a WVC does not decrease with experience. Another possible explanation is that 

young drivers drive less on the types of roadways where WVCs occur (i.e., low flow, two lane), 

resulting in relatively few WVCs for this age group. 
47 

0

0.01

0.02

0.03

0.04

0.05

1 11 21 31 41 51 61 71 81 91

Driver Age

Proportion of Collisions

All

AVC

Figure 21. Graph. Age distribution for all crashes and AVCs (HSIS data). 

To further investigate the relationship between age and WVCs, the National Household Travel 

Survey and U.S. Census data were combined to estimate a VMT breakdown by age group.(64,65)

This VMT was used to determine a crash rate by age category for the GES data. Young drivers 

(age 15–19) had a crash rate 3.7 times higher than middle-age drivers (age 25–54) for all crashes. 

For AVCs, younger drivers still had a higher crash rate than middle- age drivers (2.1 times as 

high), but it is clearly not as large an increase as for the typical crash. 

It should be noted that although age may not play as much of a role in being involved in a WVC, 

it does play a role in being injured. As noted previously, Conn and others found that persons 

between ages 15 and 24 were by far the highest category of emergency room injuries attributed 

to WVCs.(15) 

SUMMARY 

This review of the national crash databases showed that AVCs have become more important, in 

both absolute and relative numbers. The total number of WVCs is increasing at a rate of 

approximately 6,800 more WVCs per year. Deer populations have also continued to increase in 

many areas within the United States. The review of reported crashes for large animals showed 

that WVCs are more commonly or typically as follows: 

• On rural, two-lane, low-flow, high-speed roadways. 

• During early morning and late evening hours. 

• Within spring and fall months. 

• Lower-severity crashes (high-severity WVCs are more commonly motorcycle crashes). 

• Comparative in proportion of crashes for the younger and medium-age driver categories. 

• In locations with high wildlife populations, especially deer. 
48 

• With deer (mule deer and white-tailed deer combined). 

• In areas with many transitions from cover to more open habitat, riparian habitat, shrub 

land (for white-tailed deer) and large drainages and known seasonal migration corridors 

(for mule deer). 

• Near forested cover and drainages. 

• On dry, straight roadways. 

• Single-vehicle collisions. 

This review also showed that the availability of consistent and detailed WVC data is limited, the 

data do not always distinguish between species or species groups, and the data suffer from severe 

underreporting. Furthermore, reliable WVC data for small or medium size species or threatened 

or endangered species do not exist on a national level. 
49 

CHAPTER 3. ECONOMIC IMPACTS OF WILDLIFE-VEHICLE COLLISIONS 

This chapter describes the costs associated with WVCs. It focuses on impacts that can be 

converted to monetary values. There are other impacts associated with WVCs that may not be 

easily quantifiable. Nonetheless, the cost estimates that are presented are an important 

component in justifying potential mitigation measures to reduce WVCs. 

METHODS 

Western Transportation Institute (WTI) researchers estimated the costs for WVCs in two ways. 

First, they estimated the costs for the average WVC based on property damage, human injuries 

and human fatalities. Secondly, they estimated the costs for species-specific WVCs for deer, elk, 

and moose-vehicle collisions (Alces alces). For this second analysis, the parameters included 

were vehicle repair costs, costs associated with human injuries and fatalities, towing, accident 

attendance and investigation, the monetary value of the animal that was killed in the collision 

(based on hunting fees and other recreational values), and the cost of disposal of the animal 

carcass. 

AVERAGE ANIMAL-VEHICLE COLLISION 

The total estimated cost of the average AVC based on property damage, human injuries, and 

human fatalities is $6,126 (table 4). More than 95 percent of all AVCs result in property damage 

only (table 4), at an average cost over all collisions of $2,451. While human injuries and 

fatalities occur in less than 5 percent of all collisions, their associated costs per collision are 

substantially higher, driving up the cost of the average AVC to the $6,126 value. 

For the analyses described above, 1994 USDOT estimates of motor vehicle accident costs were 

used, corrected for the Gross Domestic Product Deflator through the fourth quarter in 2006.(66,67)

The 1994 USDOT cost estimates relate to all types of motor vehicle accidents, including, but not 

exclusively, AVCs. The severity categories for human injuries, including a “possible human 

injury” are based on police reports at the scene of the accident. The 1994 USDOT cost estimates 

factor in that some of these “possible human injuries” later show to be injuries indeed, while 

others are not. The distribution of AVCs across the maximum severity categories is based on the 

data presented in figure 9 in chapter 2 of this report and specifically relates to AVCs. 
50 

Table 4. Estimated costs for property damage, human injuries, and human fatalities for the 

average AVC. 

Maximum Severity Cost ($) 

Distribution of 

Collisions (%) 

Contribution to Cost of 

Average AVC ($) 

Property damage only 2,570 95.37 2,451 

Possible human injury 24,418 2.34 572 

Evident human injury 46,266 1.75 809 

Incapacitating/severe 

human injury 231,332 0.47 1,083 

Human fatality 3,341,468 0.04 1,210 

Total 1.00 6,126 

DEER-, ELK-, AND MOOSE-VEHICLE COLLISIONS 

Based on a review of the literature, the probability that a collision with a deer, elk, or moose 

would result in property damage, a human injury, and a human fatality was estimated. In 

addition, estimates were made of the amount of property damage (vehicle repair costs) as a result 

of a collision with these three species. 

The species-specific cost estimates were made using the same base cost estimates and categories 

for human injuries as in table 4. Since it was not possible to distinguish among the three injury 

categories when calculating the species-specific probabilities that a collision would result in a 

human injury, the relative frequency of each of the three injury categories was determined using 

the values in table 4. This approach produced the following values: 51.4 percent of all human 

injuries involved possible human injuries, 38.4 percent of all human injuries involved evident 

human injuries, and 10.3 percent of all human injuries involved incapacitating or severe human 

injuries. 

VEHICLE REPAIR COSTS 

In Nova Scotia, the percentage of collisions involving white-tailed deer that resulted in property 

damage was estimated at 90.2 percent—3,524 collisions with property damage out of 

3,905 collisions.(68) In Utah this percentage was estimated at 94 percent.(3) There were no similar 

data available for elk or moose. For this analysis the percentage of collisions resulting in 

property damage was assumed to be 92 percent for collisions with deer, 100 percent for 

collisions with elk, and 100 percent for collisions with moose. Property damage (repair costs for 

vehicles) has been estimated by a number of studies: 

• Romin and Bissonette estimated the value at $1,200 ($1,881 for deer in Utah and 

Vermont) in 1992.(3) 
51 

• In British Columbia, the costs for deer collisions with passenger vehicles were estimated 

at Can$1,222.(69)

• The cost for deer collisions on average for different regions in the United States in 1993 

were estimated at $1,577.(4)

• In New Mexico, the average vehicle repair cost of an elk-vehicle collision was estimated 

at $3,448, based on seven collisions.(70) 

• Vehicle repair costs resulting from a collision with a moose in north central British 

Columbia can be as high as Can$25,000, but they averaged Can$5,150 in 1999.(71) 

• In British Columbia, the estimated average claim for a DVC was Can$1,222 and a 

moose-vehicle collision was Can$3,358.(69) 

• Other studies in British Columbia estimated moose-vehicle collisions at Can$2,200 in 

2000 and Can$2,800 in 2001.(68,72) 

• An average value of $2,300 was reported for the United States in 2002.(73) 

Based on these various values, it was assumed for this analysis that the average vehicle repair 

costs as a result of AVCs were $2,000 for deer, $3,000 for elk, and $4,000 for moose. Combined 

with the percentage chance that a collision indeed results in property damage (see earlier), the 

vehicle repair costs for an average AVC with each species were estimated at $1,840 (deer), 

$3,000 (elk), and $4,000 (moose). 

HUMAN INJURIES 

AVCs can cause human injuries. (See references 4, 15, 29, 68, and 74.) In the United States, 

AVCs were estimated to result in 26,647 human injuries per year (average for 2001–2002).(15)

An estimated 22,498 of these human injuries resulted from collisions with larger animals, mostly 

with deer (86.9 percent). An estimated 12.2 percent were the result of collisions with horses 

(Equus sp.) and bovines (Bos sp.). Elk, moose, and bear (Ursus sp.) accounted for the remaining 

0.8 percent.(15) 

The percentage of white-tailed deer-vehicle collisions resulting in human injuries was estimated 

at 1.3 percent in Finland; 3.8 percent in the U.S. Midwest; 4 percent in Ohio, 4 percent across the 

U.S., 7.7 percent in Ohio; and 9.7 percent in Nova Scotia. (See references 4, 53, 62, 68, and 75.) 

The percentage of moose-vehicle collisions resulting in human injuries was estimated at 

9.9 percent in Finland, 11.2 percent in Sweden, 18 percent in Newfoundland and Labrador, 21.8 

percent in Newfoundland, 23 percent in Maine (figure 11, chapter 2), 20 percent in rural Alaska, 

and 23 percent in Anchorage, AK. (See references 68, 75, 76, 77, 78, and 79.) The ratio of 

moose-vehicle collisions to human injuries was estimated at 1:0.201 in Newfoundland and 

1:0.304 in Anchorage, AK.

(79,80) The ratios are higher than the percentages, because more than 

one person may be present in a car, and multiple people may be injured as a result of one 

collision. For this analysis it was assumed that an AVC resulted in an average of 0.05 human 
52 

injuries for deer, 0.10 human injuries for elk, and 0.20 human injuries for moose. When these 

proportions are combined with the relative frequency for each of the three injury categories 

(51.4 percent for possible human injuries, 38.4 percent for evident human injuries, and 10.3 

percent for incapacitating or severe human injuries), it results in the cost estimates for human 

injuries by species presented in table 5. The costs of human injuries by species type are $2,702 

(deer), $5,403 (elk), and $10,807 (moose) for each collision. Note that the costs in table 4 

and table 5 cannot be directly compared. The costs in table 4 are for all AVCs, regardless of the 

species, while the costs in table 5 relate to specific wildlife species. In addition, for table 4 the 

chances that a reported AVC results in a human injury are based on GES data (table 8), while 

for table 5 these chances are based on a species-specific review of the literature.

Table 5. Costs for types of human injuries for the average deer-, elk-, and moose-vehicle 

collision. 

Type of Human Injury Deer Elk Moose 

Possible $627 $1,254 $2,508 

Evident $887 $1,775 $3,550 

Incapacitating/severe $1,187 $2,374 $4,749 

Total $2,702 $5,403 $10,807 

HUMAN FATALITIES 

While rare, AVCs can cause human fatalities. (See references 4, 13, 68, and 74.) The percentage 

of white-tailed deer-vehicle collisions resulting in human fatalities was estimated at 0.009 

percent in Ohio (14 collisions with human fatalities from 143,016 collisions), 0.029 percent in 

North America, 0.03 percent in the U.S. Midwest (33 collisions with human fatalities from 

125,608 collisions), and 0.05 percent in Nova Scotia (2 collisions with human fatalities from 

3,905 collisions).(53,62,68) 

White-tailed deer are the most common species involved in fatal WVCs. A study that used data 

from nine states (Colorado, Georgia, Minnesota, Missouri, North Carolina, Ohio, Pennsylvania, 

South Carolina, and Wisconsin) showed that 77 percent of these fatal accidents involved whitetailed deer.(13) 

The percentage of moose-vehicle collisions resulting in human fatalities was estimated at 

0 percent in Anchorage, AK (0 fatalities from 519 collisions), 0.26 percent in Newfoundland 

(14 fatalities from 5422 collisions), 0.36 percent in Newfoundland (6 collisions with human 

fatalities from 1662 collisions), 0.45 percent in Newfoundland (3 fatalities from 661 collisions), 

0.43 percent in Maine (figure 11, chapter 2); 0.5 percent in Sweden, and 0.50 percent in rural 

Alaska. (See references 8, 68, 76, 78, 79, and 80.) 

For this analysis it was assumed that an AVC resulted in an average of 0.0005 (deer), 

0.0020 (elk), and 0.0040 (moose) human fatalities. When these proportions are combined with 

the cost listed in table 4, it results in a cost estimate for human fatalities of $1,671 (deer), 

$6,683 (elk), and $13,366 (moose) for each collision. Note that these estimates cannot be directly 
53 

compared with those in table 4. The costs in table 4 are for all AVCs, regardless of the species, 

while the cost estimates in this paragraph relate to specific wildlife species. In addition, for 

table 4 the chances that a reported AVC results in a human fatality are based on GES data (table 

8), while the chances for the cost estimates in this paragraph are based on a species-specific 

review of the literature. 

TOWING, ACCIDENT ATTENDANCE, AND INVESTIGATION 

Not all WVCs require the towing of a vehicle and attendance or investigation by medical 

personnel, fire department personnel, or police. When they do, the cost for these efforts was 

estimated to vary between Can$100 and 550.(69) Note that the cost for the actual medical 

assistance is included in the cost estimates for human injuries calculated earlier. For this analysis 

it was assumed that the cost of towing and accident attendance or investigation is $500, but these 

services are only required in 25 percent (deer), 75 percent (elk), and 100 percent (moose) of the 

collisions. These assumptions result in an average cost for towing, accident attendance, and 

investigation of $125 (deer), $375 (elk), and $500 (moose) per AVC. 

MONETARY VALUE OF ANIMALS 

Animals usually die immediately or shortly after having been hit by a vehicle. In Michigan, 

Allen and McCullough estimated that a minimum of 91.5 percent of all white-tailed deer that 

were hit by a vehicle died at the scene or shortly thereafter.(81) In Newfoundland, 88.5 percent of 

all moose collisions resulted in the death of the animal (4,800 moose fatalities out of 

5,422 collisions). For this analysis, it was assumed that an AVC always resulted in the eventual 

death of the animal, regardless of the species. 

The monetary value of wildlife has many different components, including license fees, costs 

associated with hunting (e.g., materials, transport, lodging, meals), and recreational wildlife 

viewing. Hunting license fees in British Columbia were Can$15–125 for deer, Can$25–200 for 

elk, and Can$25–200 for moose, for residents and non-residents, respectively.(72) The net return 

to the economy of British Columbia from hunting was estimated at Can$1,270–7,450 for deer, 

Can$3,250–3,290 for elk, and Can$1,250–1,680 for moose.(72) The total net return to the 

economy of British Columbia from recreational wildlife viewing was estimated at 

Can$174,000,000 per year.(72) There were an estimated 681,000 large mammals present in 

British Columbia, including black bears (Ursus americanus), grizzly bears (Ursus arctos), 

caribou (Rangifer tarandus), mule deer, and black-tailed deer (Odocoileus hermionus 

columbianus), white-tailed deer, elk, moose, and bighorn sheep (Ovis canadensis).(72) From this 

information, an average value for recreational wildlife viewing per large mammal was estimated 

at Can$255. 

In New Mexico, the minimum estimated income to the state as a result of hunting was estimated 

at $250 for each deer and $500 for each elk, excluding hunter expenditures and associated 

economic benefits.(70) In Utah, Romin and Bissonette estimated the economic value of a deer at 

$1,313 in 1992.(3) Bissonette and Hammer estimated the value of deer in Utah in 1999 at 

$2,420.(82) Based on this information, it was assumed that the total monetary value of each 

animal was $2,000 (deer), $3,000 (elk) and $2,000 (moose). 
54 

REMOVAL AND DISPOSAL COSTS OF DEER CARCASSES 

In Canada, the clean-up, removal, and disposal costs for animal carcasses were estimated at 

Can$100 for deer, Can$350 for elk, and Can$350 for moose.(72) In Pennsylvania, the average for 

deer carcass removal and disposal in a certified facility was $30.50 per deer for contractors and 

$52.46 per deer for the Pennsylvania Department of Transportation in 2003–2004 (Jon Fleming, 

Pennsylvania Department of Transportation, personal communication). For this analysis, it was 

assumed that the removal and disposal costs of animal carcasses were $50 (deer), $100 (elk), and 

$100 (moose). 

OTHER COSTS 

Examples of costs that are not easily quantifiable and that were excluded from these analyses are 

the costs associated with emotional distress of people involved in WVCs, the expenses involved 

with conservation efforts for threatened or endangered species, the costs of the distress of injured 

animals, the costs associated with the rehabilitation of injured animals, and the cost of cultural 

values impacted by wounded animals (e.g., native Americans or other groups in society). 

Wildlife rehabilitators in Connecticut estimated that 36 percent of all reptiles and amphibians, 

6 percent of all birds, and 12 percent of all mammals admitted to wildlife rehabilitation centers in 

Connecticut between 1996 through 2005 suffered from wounds inflicted by vehicles (Laurie 

Fortin, State of Connecticut, Department of Environmental Protection, personal communication). 

The total number of individuals (all species groups combined) that suffered from wounds 

inflicted by vehicles was 896 per year. At an average cost of $150–200 per individual medical 

examination and treatment (visits to veterinarian, X-rays, medication, etc.), the yearly wildlife 

rehabilitation costs in Connecticut are estimated at $134,400–179,200 (Laura Simon, 

Connecticut Wildlife Rehabilitators Association, personal communication). 
55 

SUMMARY 

The cost of WVCs is summarized in table 6. Bear in mind that this analysis is based on a series 

of assumptions and estimates that may need to be modified as more and better data become 

available. A national estimate of vehicle collisions with moose or elk is unavailable. However, 

based on a total estimate of one million DVCs per year in the United States, the estimated total 

cost associated with WVCs is calculated to be $8,388,000,000 (per year in the United States). 

Note that collisions with smaller animal species (smaller than deer) and domesticated species 

(e.g. livestock) were not included in this calculation. 

Table 6. Summary of estimated costs of a WVC for a deer, elk, and moose. 

Description Deer Elk Moose 

Vehicle repair costs per collision $1,840 $3,000 $4,000 

Human injuries per collision $2,702 $5,403 $10,807 

Human fatalities per collision $1,671 $6,683 $13,366 

Towing, accident attendance and investigation $125 $375 $500 

Monetary value animal per collision $2,000 $3,000 $2,000 

Carcass removal and disposal per collision $50 $100 $100 

Total $8,388 $18,561 $30,773 

57 

CHAPTER 4. IMPACTS TO WILDLIFE 

Roads and traffic can negatively affect wildlife in various ways, including habitat loss, reduced 

habitat quality, reduced habitat connectivity (and associated potential demographic and genetic 

consequences), and direct road mortality. (See references 83, 84, 85, and 86.) This chapter 

focuses on the effects of direct road mortality on wildlife only, specifically for threatened and 

endangered species. 

As previously stated, in most cases, an animal that has been hit by a vehicle dies immediately or 

shortly after the collision. For example, in Michigan, Allen and McCullough estimated that a 

minimum of 91.5 percent of all white-tailed deer that were hit by a vehicle died at the scene or 

shortly thereafter.(81) In Newfoundland, 88.5 percent of all moose collisions resulted in the death 

of the animal (4,800 moose fatalities out of 5,422 collisions). Many different wildlife species 

representing a wide variety of species groups have been observed as roadkill, sometimes in 

massive numbers. Seiler provided a review of estimates of the number of road-killed animals.(23)

The combined number of road-killed amphibians, birds, ungulates, and other vertebrates runs in 

the multiple millions per year for most of the countries that were reviewed. In the United States 

the total number of road-killed vertebrates was estimated at 365 million per year.(87) The number 

of DVCs in the United States was estimated to exceed 500,000 per year, around 538,000 per 

year, and greater than 1,000,000 per year.(3,4,45) 

The number of WVCs and animal carcasses is often underestimated (as previously discussed in 

chapter 2); researchers have calculated the underestimation by 10.3 percent, 25 percent, 

50 percent, 77.5 percent, and 87.9 percent. (See references 4, 68, 72, and 88.) These estimates for 

underreporting apply especially to deer, as this species is involved in the vast majority of all 

reported AVCs or large WVCs in North America; for example, 80 percent in Saskatchewan, and 

81.4 percent in Maine.(68,89) Underreporting may have various causes, including infrequent 

carcass checks, poor visibility of the carcass from the road, mutilation of the carcass by traffic to 

the point that the species can no longer be identified or that little to none of the carcass remains, 

decomposition, (illegal) removal by humans other than the data collectors, and scavengers.(90) 

While deer are the species of primary interest from a safety perspective, their survival probability 

is typically not a concern. Species most affected in their population survival probability seem to 

be species that have relatively low population density, large home ranges, travel long distances, 

are long lived, and have a relatively low reproduction rate. (See references 85, 91, 92, and 93.) 

Roads and traffic can reduce population densities for some species such as different frogs and 

toads, the western European hedgehog (Erinaceus europaeus), and the desert tortoise (Gopherus 

agassizii).(94, 95, 96) For some species, the survival probability of local or regional populations can 

be impacted too, especially if the species concerned also suffer from other human-related 

disturbances such as large-scale intensive agriculture and urban sprawl.(97,98) The effect of road 

mortality on the population viability of a species can not always be separated from other effects 

associated with roads and traffic, but road mortality is believed to have affected the population 

survival probability for multiple species representing different species groups: amphibians (moor 

frog (Rana arvalis)), (leopard frog (Rana pipiens); spotted salamander (Ambystoma 

maculatum)), reptiles (timber rattlesnakes (Crotalus horridus)), (land and large bodies pond 
58 

turtles including the box turtle (Terrapene ornata)), mammals (western European hedgehog), 

(Eurasian badger (Meles meles)), (otter (Lutra lutra)), (ocelot (Leopardus pardalis)), (Florida 

panther (Felis concolor coryi)), (Iberian lynx (Lynx pardinus)), (Florida Key deer (Odocoileus 

virginianus clavium)). (See references 91, 92, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 

109, and 110.) 

THREATENED AND ENDANGERED SPECIES 

This section reviews federally listed threatened and endangered animal species in the United 

States for which direct road mortality is among the major threats to the survival of the species or 

certain populations of that species. The threatened and endangered species were not reviewed 

with regard to other effects associated with roads and traffic such as habitat loss, reduced habitat 

quality, and the barrier effect of transportation infrastructure. Note that the list in this chapter 

(table 7) has no regulatory status and that it does not replace potential consultation with the 

appropriate agencies about the impact of road improvement projects on local endangered species. 

In addition, because the required data were often difficult to access, and since only limited time 

was available for this effort, the list in this chapter is not necessarily complete. 

METHODS 

All threatened and endangered animal species (clams, snails, crustaceans, arachnids, insects, 

fishes, amphibians, reptiles, birds, and mammals) in each of the 50 states and Washington, DC, 

were combined into one list. If different populations of the same species were listed, they were 

treated separately.(111) Species (or populations) were identified for which direct road mortality is 

among the major threats to the survival probability of the species. Species that are aquatic were 

not reviewed with regard to vehicle collisions. Mortality as a result of collisions with trains and 

off-road vehicles was also excluded from the review. This review focused solely on the effect of 

direct mortality resulting from vehicle collisions (e.g., cars and trucks) on paved roads (e.g., 

asphalt or concrete). 

The following sources were used to evaluate whether direct road mortality is a major threat to the 

survival probability of threatened and endangered species: (1) documents that provided a 

rationale for the listing of threatened and endangered species (Federal Register publications), 

(2) the 2006 International Union for Conservation of Nature and Natural Resources Red List of 

Threatened and Endangered Species, (3) other sources, including publications on individual 

species or species groups and expert opinions (appendix A).(112) If an expert opinion was the sole 

source of information that direct road mortality is among the major threats to the survival of a 

certain species, additional quantitative information was sought out on the importance of road 

mortality before the species was added to table 7. In addition, speculations alone about the 

potential impact of direct road mortality were not sufficient for a species to be listed in this 

chapter. 

The list presented in this chapter is not necessarily complete because the required information 

was difficult to access and the time available for this effort was limited. Furthermore, some 

species have been listed for decades and circumstances have changed or more and better 

knowledge about the threats to individual species has become available since the original listing 

documents were published. For these reasons one cannot only rely on the original listing 
59 

documents. Other sources have to be included in determining whether the survival probability of 

a species is substantially impacted by road mortality. 

Even though the information available was carefully evaluated, the process of including and 

excluding species from the species listed in this chapter was at least partially subjective. Because 

of the diverse and inconsistent nature of the sources and data available, the inclusion or exclusion 

from the list could not be based on a simple definition. The inclusion or exclusion of the species 

listed relied, at least to a certain extent, on expert judgment that is open to debate. Furthermore, 

just as the status of species and circumstances have changed since the original listing documents 

were published (discussed above), the status and circumstances will continue to change and the 

list presented in this chapter will become less applicable over time. 

RESULTS 

For the 21 species listed in table 7, direct road mortality is considered a major threat to the 

survival of the species. The table includes three amphibian species, seven reptile species, three 

bird species, and eight mammal species. A brief discussion for each species follows table 7. 
60 

Table 7. Threatened and endangered species in the United States for which direct road mortality is among the m

probability of the species.(111) 

Species Group Species Name 

Sources Justifying the Inclusion of the Species Concerned 

Federal Listing 

Documents 

International Union 

for Conservation of 

Nature and Natural 

Resources Other So

Amphibians California tiger salamander 

(Ambystoma californiense), 

C. CA, S. Barb., Son. county 

(113) (112) (114,115,116) Dave Johnston, Calif

Game, California, pers

Amphibians Flatwoods salamander 

(Ambystoma cingulatum) 

(117) (112) Bruce Means, Coastal Plains Ins

Tallahassee, FL, personal com

Environmental Consulting

commun

Amphibians Houston toad (Bufo 

houstonensis) 

Threats not discussed (112) (118

Reptiles American crocodile 

(Crocodylus acutus) 

(119) Threats not discussed (120,1

Reptiles Desert tortoise (Gopherus 

agassizii), except in Sonoran 

Desert 

(122) Threats not discussed (See references 96, 1

Reptiles Gopher tortoise (Gopherus 

polyphemus), W of 

Mobile/Tombigbee Rs. 

(126) Threats not discussed (125,127

Reptiles Alabama red-bellied turtle 

(Pseudemys alabamensis) 

Collisions not listed as 

a threat 

Threats not discussed (125,129) D. Nelson, Dep. of Bio

communication, Matthew J. Are

Florida, personal 

Reptiles Bog turtle (Muhlenberg) 

northern population (Clemmys 

muhlenbergii) 

(130) Threats not discussed 

Reptiles Copperbelly water snake 

(Nerodia erythrogaster 

neglecta) 

(131) Not listed (132
61 

Table 7. Threatened and endangered species in the United States for which direct road mortality is among the m

probability of the species—continued.

Species Group Species Name 

Sources Justifying the Inclusion of the Species Concerned 

Federal Listing 

Documents 

International Union 

for Conservation of 

Nature and Natural 

Resources Other So

Reptiles Eastern indigo snake, eastern 

indigo (Drymarchon corais 

couperi) 

Collisions not listed as 

a threat 

Not listed (133,134,135) Bruce Means, Coas

Conservancy, Tallahassee, FL, p

Palis, Palis Environmental Cons

commun

Birds Audubon's crested caracara 

(Polyborus plancus audubonii), 

FL pop. 

(136) Threats not discussed (137

Birds Hawaiian goose (Branta 

sandvicensis) 

Threats not discussed (112) (138) K. Misajon, NPS, pe

Birds Florida scrub jay (Aphelocoma 

coerulescens) 

(139) (112) (140

Mammals Lower Keys marsh rabbit, 

(Sylvilagus palustris hefneri) 

Collisions not listed as 

a threat 

Threats not discussed (141,1

Mammals Key deer (Odocoileus 

virginianus clavium) 

Threats not discussed Threats not discussed (143

Mammals Bighorn Sheep, Peninsular CA 

pop. (Ovis canadensis) 

(144) Threats not discussed 

Mammals San Joaquin kit fox (Vulpes 

macrotis mutica) 

Threats not discussed (112) (145

Mammals Canada lynx (Lynx 

canadensis), lower 48 states 

(146) Collisions not listed as a 

threat 

(147) Alison Michael, U.S. F

communication; Phil Delphey, U

personal com

Mammals Ocelot (Leopardus pardalis) Collisions not listed as 

a threat 

Collisions not listed as a 

threat 

(107,1

Mammals Florida panther (Felis concolor 

coryi) 

Threats not discussed Collisions not listed as a 

threat 

(149

Mammals Red wolf (Canis rufus), except 

where XN 

Collisions not listed as 

a threat 

(112)
 62 

Amphibians 

The California tiger salamander (Ambystoma californiense) is affected by habitat loss due to 

urbanization and agriculture, unnatural hydrology, predation by nonnative species (bullfrogs, 

crayfish, various fish species), reduced availability of burrows as a result of rodent control 

programs, vehicle collisions, reduced food availability through the use of pesticides for mosquito 

control, hybridization with nonnative tiger salamanders, and storm water road runoff (Dave 

Johnston, California Department of Fish and Game, CA, personal communication). (See 

references 112, 113, 114, 115, and 116.) 

The flatwoods salamander (Ambystoma cingulatum) was listed because of habitat loss and 

habitat alteration.(117,150) However, direct mortality (road mortality during migration, capture by 

bait collectors) is also a potential or a major threat to this species (Bruce Means, Coastal Plains 

Institute and Land Conservancy, Tallahassee, FL, personal communication; John Palis, Palis 

Environmental Consulting, Jonesboro, IL, personal communication).(112,117) At one location 

where a substantial population decline has been observed, road mortality was not considered 

substantial. In this case, habitat loss and habitat degradation (agriculture, silviculture, 

urbanization, and changes in hydrology, predation by nonnative fish species) are thought to be 

the primary cause of the decline.(151) Silviculture is the cultivation and management of forest 

trees or woodlands for producing timber and other wood products. 

The Houston toad (Bufo houstonensis) is affected by habitat loss and habitat alteration, mostly 

through urbanization, recreational development, and agriculture.(112,118) However, direct road 

mortality through increased habitat fragmentation by road construction has also been identified 

as a major threat to the survival probability of the species.(112,118) Other threats include predation 

by nonnative species (e.g., Brazil fire ants).(112) 

Reptiles 

The American crocodile (Crocodylus acutus) is affected by changes in hydrology and 

consequent changes in salinity levels.(121) In addition, direct mortality of adult American 

crocodiles is considered higher than the population can sustain.(121) Of the deaths recorded 

between 1971 and 2001, the majority were hit by cars.(119,120,121) Warning signs and fences were 

installed along the major highways throughout crocodile habitat in south Florida.(119) However, it 

appears that some or all of the planned underpasses may not have been built (U.S. Highway 1) 

and that some of the fencing that was installed (State Route 905) was not flush with the ground 

so that American crocodiles could enter but not exit the right of way. Some of these fence 

sections have now been removed (Frank Mazzotti, Department of Wildlife Ecology and 

Conservation, Fort Lauderdale Research and Education Center, Davie, FL, personal 

communication). 

The desert tortoise (figure 22) is affected by habitat loss (agriculture, landfills) and habitat 

degradation (e.g., through off-road vehicle use, overgrazing, invasive plant species). (See 

references 96, 123, 152, and 153.) Substantial direct mortality occurs on highways as well as off 

highways (nonintentional and intentional crushing by off-road vehicle operators, trampling of 

their burrows by off-road vehicles and livestock, shooting). (See references 96, 122, 123, 124, 

125, 152, and 153.) Other mortality causes are disease, drought, mining, wildfires, garbage and 
 63 

litter, handling by humans, collection by humans, and predation by common ravens (Corvus 

corax). (See references 96, 123, 125, 152, 154, and 155.) 

Figure 22. Photo. Desert tortoise (copyright: Marcel Huijser). 

The gopher tortoise (Gopherus polyphemus) is affected by habitat loss (urbanization, agriculture, 

silviculture, mining) and habitat degradation (silviculture, fire suppression, nonnative plant 

species).(126,127,128) Collection by humans and road mortality also affected the species 

substantially. (See references 125, 126, 127, and 128.) Furthermore, the species is affected by 

predation, including by nonnative fire ants.(128) Fences and culverts were installed along a section 

of Highway 63 in Green County, south of Leakesville, MS (Matthew J. Aresco, Nokuse 

Plantation, Bruce, FL, personal communication; Claiborne Barnwell and Chuck Walters, 

Mississippi Department of Transportation, personal communication). The aim of the mitigation 

measures is to reduce gopher tortoise road mortality and to allow for gopher tortoises to cross 

under the road (Claiborne Barnwell and Chuck Walters, Mississippi Department of 

Transportation, personal communication) (figure 23). Highway 63 has 24.1 km (15 mi) of road 

length with gopher tortoise fencing, and, because of the nature of the terrain, there is only one 

culvert that was specifically designed for the gopher tortoise (between Lucedale and Leakesville, 

MS) (Chuck Walters, Mississippi Department of Transportation, personal communication). At 

the site of the culvert, the fence stretches out about 914 m (3,000 ft) to either side of the culvert 

(Chuck Walters, Mississippi Department of Transportation, personal communication). Some of 

the fencing was installed as early as 1998, and along those road sections the number of reported 

road-killed gopher tortoises was reduced from one to two per year to zero (Chuck Walters, 

Mississippi Department of Transportation, personal communication). 
 64 

Figure 23. Photo. Fences lead gopher tortoises towards a culvert along Highway 63 in 

Green County, south of Leakesville, MS (copyright: Chuck Walters, Environmental Division, 

Mississippi Department of Transportation). 

The Alabama red-bellied turtle (Pseudemys alabamensis) is affected by egg predation, human 

disturbance, and road mortality (David Nelson, Department of Biological Sciences, University of 

South Alabama, personal communication; Matthew J. Aresco, Nokuse Plantation, Bruce, FL, 

personal communication).(125,129,156) The small population size and low recruitment rates of the 

species make recovery a difficult process. A weekly road mortality survey along the Mobile Bay 

Causeway (6.5 mi from Spanish Fort to Mobile, AL) between 2001 and 2004 reported 

324 Alabama red-bellied turtle carcasses (David Nelson, Department of Biological Sciences, 

University of South Alabama, personal communication) (figure 24 and figure 25).(129) In a 

typical year, 12–15 adult females, most of them with eggs, are found dead on the Mobile Bay 

Causeway (David Nelson, Department of Biological Sciences, University of South Alabama, 

personal communication). In addition, several dozen juveniles and a few males are killed by 

vehicles each year as well (David Nelson, Department of Biological Sciences, University of 

South Alabama, personal communication). 
 65 

Figure 24. Photo. A section of the Mobile Bay Causeway that has relatively many roadkilled Alabama red-bellied turtles (copyright: Marcel Huijser). 

Figure 25. Photo. Road-killed Alabama red-bellied turtle (copyright: Marcel Huijser). 

The northern population of the bog turtle (Clemmys muhlenbergii) is affected by habitat 

degradation and fragmentation from agriculture and development, habitat succession due to 

invasive exotic and native plants, and illegal trade and collecting.(130) In addition, roads 
 66 

contribute “significantly” to mortality, especially where roads are adjacent to or within 

wetlands.(130) 

The copperbelly water snake (Nerodia erythrogaster neglecta) is affected by habitat loss and 

habitat fragmentation, primarily because of agriculture, drainage and damming of wetlands, coal 

mining, channelization, damming and diversion of streams and rivers, and residential and 

commercial development.(131) In addition, predation by pets and vehicle-caused mortality are a 

concern.(131,132) Traffic mortality may account for mortality of 14–21 percent of the population 

per year.(132) The species seems especially vulnerable as it frequently crosses overland to 

different wetland sites.(132) 

The eastern indigo snake (Drymarchon corais couperi) is affected by habitat loss due to 

development, collection and commercial trade, intentional killing, vehicular traffic, and residual 

pesticide exposure.(135,157) In addition, gopher tortoise burrows that are gassed to kill rattlesnakes 

also unintentionally kill indigo snakes.(157) Bolt reported that road mortality was the highest 

cause of death in a study where 81 individuals were followed, some for more than three 

consecutive years.(133) At least 15 of the 38 known mortalities (39 percent) in the field were due 

to vehicles. In that study, twice as many males were killed on the road as females (M. Rebecca 

Bolt, The Dynamac Corporation, Kennedy Space Center, FL, personal communication). In 

another study, of the 31 indigo snakes documented, 5 were found dead on a road (16 percent of 

total number of individuals followed), accounting for 55 percent of all known mortalities.(134) 

Birds 

The crested caracara in central Florida (Polyborus plancus audubonii) is affected by habitat 

alteration for agriculture and housing, illegal killing, and vehicle collisions.(136,137) In a 3-year 

study, 52 percent of all fledgling mortality (14 out of 27 deaths) was caused by vehicle 

collisions.(137) The crested caracara spends substantial time close to roads as it searches for and 

feeds on road-killed animals (Dan Smith, Western Transportation Institute, Montana State 

University, personal communication). 

The Hawaiian goose, or nene (Branta sandvicensis), is affected by habitat loss, predation by the 

nonnative small Indian mongoose (Herpestes auropunctatus), dogs, and perhaps rats and 

cats.(112) Poaching and roadkills are also important causes of mortality (Kathleen Misajon, 

National Park Service, personal communication).(112,138) Road mortality is the most common 

known cause of mortality in adults.(158) The species may also be affected by diseases and 

parasites, inbreeding depression, loss of adaptive skills in captive-bred birds, and dietary 

deficiencies.(112) 

Haleakala National Park reported 35 road-killed Hawaiian geese between 1973 and 2006, and 

Hawai'i Volcanoes National Park reported 33 road-killed Hawaiian geese between 1996 and 

2006 (Kathleen Misajon, National Park Service, personal communication). The population size 

of the Hawaiian goose fluctuated between 140 and 200 between 1996 and 2006 (Kathleen 

Misajon, National Park Service, personal communication). In Hawai’i Volcanoes National Park, 

five adult Hawaiian geese have been killed on the road in 2006 between January 1 and August 

28, out of a total of 160 individuals (Kathleen Misajon, National Park Service, personal 

communication). 
 67 

In Hawai’i Volcanoes National Park, the Hawaiian goose is attracted to roads because of feeding 

by park visitors, especially around parking areas (Kathleen Misajon, National Park Service, 

personal communication) (figure 26). This practice habituates the birds to roads and cars, and it 

encourages them to spend more time on and alongside roads, increasing their exposure to 

vehicles. Furthermore, some road sections in the park split roosting habitat from feeding habitat. 

When they have young, Hawaiian geese walk between roosting and feeding sites for 3–4 months 

and cross the road frequently, mostly at dawn or dusk, with relatively low visibility (Kathleen 

Misajon, National Park Service, personal communication). Pairs with goslings are basically 

pedestrian until the goslings fledge at 3–4 months of age. 

Permanent warning signs have been installed in known Hawaiian goose kill areas (Kathleen 

Misajon, National Park Service, personal communication) (figure 27). In addition, temporary 

warning signs can be installed at new or unexpected locations. Nonetheless, all five individuals 

that were killed by vehicles between January 1 and August 28, 2006 were within signed crossing 

zones (Kathleen Misajon, National Park Service, personal communication). There are also 

indirect effects of roadkills to the Hawaiian goose population. For example, mates are left 

without partners, often for at least one breeding season, resulting in one less nesting attempt that 

year (Kathleen Misajon, National Park Service, personal communication). In addition, goslings 

without one or both parents have substantially reduced survival probability (Kathleen Misajon, 

National Park Service, personal communication). 
 68 

Figure 26. Photo. “Do Not Feed Nene” sign (copyright: Hawai’i Volcanoes National Park, 

National Park Service). 

Figure 27. Photo. Hawaiian goose (nene) warning sign (copyright: Haleakala National Park, 

National Park Service). 

The Florida scrub jay (Aphelocoma coerulescens) is affected by habitat loss (housing 

developments, citrus-groves) and reduced habitat quality (disrupted fire regimes, human 
 69 

disturbance), predation by nonnative species (feral cats) and roadkill. (See references 112, 139, 

140, and 159.) Annual mortality rates of the Florida scrub jay have been recorded to be 65 

percent higher in road territories compared to nonroad territories.(140) Furthermore, roadside 

territories are a population sink, and the high mortality rate appears to be caused by vehicle 

collisions rather than other factors associated with a roadside environment.(140) 

Mammals 

The Lower Keys marsh rabbit (Sylvilagus palustris hefneri) is or has been affected by wetland 

drainage for residential, commercial and military purposes, habitat destruction associated with 

road building, hunting, predation by feral house cats, road mortality, mowing practices, and offroad vehicle use.(117,160) In a combination of a field and modeling study, almost one-third of all 

mortalities were caused by vehicle collisions, and modeling showed that theoretical removal of 

road mortality would eliminate the chance of extinction for the Big Pine metapopulation.(141)

Dispersing subadult males seem especially vulnerable to traffic mortality.(117) 

The Florida Key deer (Odocoileus virginianus clavium) is affected by vehicle collisions, habitat 

loss, and human disturbance.(110,143) Vehicle collisions account for more than 50 percent of the 

total deer mortality, mostly on U.S. Highway 1.(143) 

The bighorn sheep, peninsular California population, (Ovis canadensis) is affected by a range of 

issues including disease, low recruitment, habitat loss, habitat degradation, habitat fragmentation, 

residential and commercial development and high predation rates.(144) This population, especially 

small groups that have low recruitment, is also threatened by road mortality.(144) 

The San Joaquin kit fox (Vulpes macrotis mutica) is threatened by habitat conversion 

(agriculture, urban development, industrial development), habitat fragmentation, loss of prey 

species (e.g., eradication of prairie dog towns), predation (coyotes, bobcats, nonnative red foxes, 

and domestic dogs), and vehicle mortality.(112,145,161) In the San Joaquin Valley of California, 

habitat conversion for agriculture has slowed, but habitat loss, reduction of habitat quality, and 

habitat fragmentation are still a primary threat. Road mortality varies between studies: 20 out of 

225 adult deaths (9 percent), 11 out of 142 juvenile deaths (8 percent), 1 out of 60 deaths 

(2 percent), 1 out of 22 deaths (5 percent), 2 out of 49 deaths (4 percent), 2 out of 17 deaths 

(12 percent), 15 out of 23 adult deaths (65 percent), and 6 out of 12 juvenile deaths 

(50 percent).(145) After predation, vehicle collisions are likely to be the second most common 

cause of mortality.(145) 

Canada lynx (Lynx canadensis) is likely impacted by urbanization and forestry practices 

(including fire suppression) and trapping.(162,163) In addition, its population size fluctuates with 

the availability of its main prey species, the snowshoe hare (Lepus americanus).(163) In the United 

States, road mortality may limit the reestablishment of the Canada lynx in Wisconsin and 

Michigan.(146) A total of 218 adult lynx were released between 1999 and 2006, and there were 

80 known mortalities as of June 30, 2006.(147) Starvation was a substantial cause of mortality in 

the first year of the releases only. About 31.3 percent of the known mortalities were human 

induced (including collisions with vehicles or shooting by humans).(147) Malnutrition and disease 

or illness accounted for 21.3 percent of the deaths, while 32.5 percent of the deaths were from 

unknown causes.(147) Closer and more recent analyses showed that road mortality accounted for a 
 70 

minimum of 44 percent (11 out of 25) of human-caused mortalities (Alison Michael, U.S. Fish 

and Wildlife, personal communication). This percentage may be higher as this estimate only 

included confirmed vehicle-caused mortality and excluded suspected vehicle-caused mortality 

(Alison Michael, U.S. Fish and Wildlife, personal communication). In Maine, 11 road-killed 

Canada lynx have been reported since 1999; nine on two-lane logging roads that are also 

accessible to the public and two on paved public roads.(164) Recent data from Minnesota show 

that Canada lynx have died from shooting, trapping, collisions with trains, and road mortality 

(Phil Delphey, U.S. Fish and Wildlife Service, personal communication). Road mortality on 

paved highways amounted to 17 percent (5 out of 30) of all known mortalities since the species 

was listed in 2000 (Phil Delphey, U.S. Fish and Wildlife Service, personal communication). 

The ocelot is affected by habitat loss (loss of dense thorn shrub habitat), mortality vehicle 

collisions, and genetic erosion.(107,148,165) Vehicle collisions constituted 35 percent of all 

mortality.(148)

The Florida panther is affected by habitat loss (agriculture, urbanization), habitat fragmentation, 

road mortality, and loss of genetic diversity .(166,167,168) Road mortality is substantial, 25 out of 

73 deaths were caused by vehicles.(149) 

The red wolf (Canis rufus) went extinct in the wild by 1980 and was reintroduced in 1987 in 

North Carolina.(112) After reintroduction, the species was affected by hybridization with coyotes 

(Canis latrans) .(112,169,170) Direct mortality (vehicle collisions, shooting) can be substantial.(112) 

Other Species 

In addition to the species listed in table 7, the authors of this report recognize that other federally 

threatened and endangered species may be substantially affected by road mortality too. However, 

species that had insufficient data available, at least to the authors of this report at the time of 

publication, were excluded from table 7. 

Summary 

This chapter identified 21 federally listed species from four species groups (amphibians, reptiles, 

birds and mammals) for which direct road mortality is among the major threats to the survival of 

the species. However, road mortality is typically only one of the major threats to these species. 

Habitat loss (e.g., due to agriculture, urbanization, mining, and changes in hydrology), reduced 

habitat quality (e.g., due to agricultural and silviculture practices such as livestock grazing, 

logging, fire suppression, introduction of nonnative plant species, and water contamination with 

pollutants, and the use of pesticides, in general), habitat fragmentation (e.g., due to roads or other 

unsuitable habitat), competition and predation by nonnative species, other sources of natural and 

unnatural mortality (e.g., off-road vehicles, poaching, direct killing or collection by humans, 

disease), and low recruitment and loss of genetic diversity due to small populations also threaten 

the survival of the species listed in this chapter. This implies that a substantial reduction in road 

mortality is not necessarily sufficient for the recovery of the species listed in this chapter. For 

successful species recovery, including mitigation for effects related to roads and traffic, it is 

advisable to use an integrated approach.(171) 
 71 

CHAPTER 5. MITIGATION METHODS THAT ATTEMPT TO INFLUENCE DRIVER 

BEHAVIOR 

This broad category of WVC mitigation strategies includes those that attempt to help drivers 

avoid a WVC by changing their behavior. The specific mitigation measures reported on in this 

chapter, by broad category based on their intent, consist of the following categories: 

• Public information and education. 

• Improvement in driver attentiveness using warning signs by: 

o Standard signs. 

o Large, nonstandard signs. 

o Seasonal signs. 

o Animal detection systems. 

• Improvement of driver attentiveness with in-vehicle warning systems by: 

o In-vehicle warning linked to roadside animal detection systems. 

o In-vehicle warning linked to on-board animal detectors. 

• Increase in visibility to drivers by: 

o Roadway lighting. 

o Vegetation removal. 

o Wider striping. 

o Reflective collars for animals. 

o Reduced height of snow banks. 

• Reduction in traffic volumes on roadways by: 

o Reduction in traffic volume on road network. 

o Temporary road closures. 

• Reduction of average speeds on roadways by: 

o Reduction of the posted speed limit. 

o Traffic calming/reduction of design speed. 

o Posting of advisory speed limits. 

• Wildlife crossing guards. 

The mitigation measures presented in the report are what might be considered by planners as 

possible mitigation measures. FHWA is not recommending any of these measures by including 

them in this report. The majority of the mitigation measures presented have been used in practice 
 72 

or at least tried as a case study, the exceptions being in-vehicle roadside animal detection linked 

to on-board computer warning and reduction in traffic volume on the road network. 

PUBLIC INFORMATION AND EDUCATION 

Increasing roadway safety via public information and driver education seeks to reduce death and 

serious injury on roadways by increasing motorists’ awareness of the impacts, causes, and highrisk locations of WVCs, as well as to give drivers advice on the best actions to take to avoid 

crashes with animals. These WVC reduction efforts are implemented through general messages 

in the media, videos, brochures, posters, and bumper stickers. Often these activities work in 

concert with roadside messages at specific high-risk locations or in specific seasons of high 

wildlife migration or movement. Public information and driver education efforts are thought to 

work best when conducted in concert with other WVC reduction techniques.(172,173) 

The most common WVCs in the United States involve deer. DVC education and information 

efforts can be divided into two categories. In one category are efforts that provide information 

describing DVC significance, such as the local rates of DVCs or locations of roadway segments 

with high rates of DVCs. In the second category are efforts that provide information on DVC 

avoidance, namely, actions drivers can take to avoid wildlife if they appear on or near the 

roadway.(53) 

Many transportation professionals and researchers have discussed driver education and public 

information campaigns as a means to help reduce WVCs or have conducted research to 

incorporate their findings into motorist education efforts. (See references 29, 38, 70, 174, 175, 

and 176.) However, there are no known studies indicating the statistical effectiveness of driver 

education or public information/awareness efforts that have directly, by themselves, decreased 

the incidence rates of WVCs.(176) 

A national phone survey indicated driver respondents believe WVCs are a serious problem, and 

more than 97 percent believe driver education and media information to the general public would 

be helpful in reducing WVCs.(175) Respondents to a survey in Michigan (1,653 questionnaires) 

are receptive to receiving more information on what actions to take to reduce their probability of 

being involved in a WVC. They indicated newspapers as the preferred medium, although they 

also chose eight other avenues of receiving information.(177) In British Columbia a survey of 

1,882 licensed drivers indicates respondents strongly (81 percent) believe wildlife warning signs 

reduce WVCs.(178) 

Public information and driver education, combined with other WVC reduction activities must 

work in concert to effectively reduce crashes and increase safety. Given a receptive audience for 

information, campaigns have great potential to tap into a public that seeks to more fully 

understand the dangers of WVCs, the actions drivers can take to avoid accidents, and the 

locations of high-risk roadways. 

Many states have developed safety campaigns to increase public awareness. For example, the 

Maine Department of Transportation’s Safety Office has a public information campaign to 

increase awareness of WVCs. They have developed a video, brochures, and crash maps for 

moose and deer at: http://www.maine.gov/mdot/safetyoffice/maine-crash-data.php (accessed 
 73 

January 25, 2007). The Iowa Departments of Transportation, Public Safety, and Natural 

Resources in conjunction with insurance agencies and local law enforcement have developed the 

“Don’t Veer for Deer” campaign. Public information maps, brochures, Public Service 

Announcements, and a poster can be found at http://www.dps.state.ia.us/commis/ 

gtsb/deercrashes/index.shtml (accessed January 25, 2007). 

The “Colorado Wildlife on the Move” Campaign reached more than three million people through 

television, magazines, and other media and included 58,000 driver safety tip sheets and 

500 posters distributed in welcome centers, national parks, and Enterprise Rent-A-Car offices in 

85 cities and 175 locations.(179) 

As a result of a local outreach campaign in Montana, survey respondents who had heard or seen 

information on WVCs increased from 21 to 33 percent.(173) 

Case Studies and Contacts 

Two relevant case studies relating to public information and education are the “Drivers for 

Wildlife” program in Jasper National Park and the program to reduce bird collisions at the 

NASA Kennedy Space Center. 

The Parks Canada Drivers for Wildlife program in Jasper National Park combines public 

education, which includes bumper stickers (see figure 28) and roadway billboards (see figure 29, 

with two digital signs that record speed and advise drivers to slow down in the high-risk wildlife 

zone. The number of road-killed animals along park highways decreased by about 15 percent 

after the first 10 months of the public education and roadside sign program; however, the signs 

were given the most credit for the reduction of WVCs.(172) 

Figure 28. Photo. Example of bumper sticker for a driver awareness campaign to reduce 

WVCs in Jasper National Park, Canada (source: Parks Canada). 

For information about Jasper National Park’s campaign, contact Brenda Shepherd, Park 

Ecologist, Jasper National Park, (780) 852-6232, brenda.shepherd@pc.gc.ca. 

In July of 2005, the space shuttle Discovery hit a vulture during take-off. Initially NASA formed 

an “Avian Abatement Team” to address this safety issue. The program has been expanded to 

include prevention of roadkill (which attracts the birds) in concert with the Merritt Island 

National Wildlife Refuge, which is a 140,000-acre overlay of the Kennedy Space Center. The 

refuge provides a buffer zone for NASA. 
 74 

Figure 29. Photo. Roadside billboard along highway in Jasper National Park, Canada 

(source: Parks Canada). 

The Kennedy Space Center has developed a Web site with a video, materials, posters (see figure 

30), stickers and updates on the latest roadkill statistics at: http://environmental.ksc.nasa.gov/ 

projects/roadkill.htm (accessed January 25, 2007). 

The Web site includes a link to the FHWA’s Critter Crossings Web site 

at: http://www.fhwa.dot.gov/environment/wildlifecrossings/index.htm (accessed January 25, 

2007). 
 75 

Figure 30. Photo. Poster created by NASA’s John F. Kennedy Space Center as part of its 

RoadKill Prevention Program (source: NASA). 

Direct Benefits 

The Iowa Department of Transportation’s Don’t Veer for Deer campaign appears to be 

demonstrating benefits. Since implementation of this program the number of fatalities resulting 

from deer-car collisions dropped 60 percent in 2005, from 10 in 2003 to 4 in 2005, according to 

their Web site (http://www.dps.state.ia.us/commis/pib/Releases/2006/10-05-2006_Deer.htm).(180)

The long-term effect requires further study. 

The reduction in severity (i.e., number of fatalities) is a positive benefit, but no campaigns 

identified the direct level of correlation between public information and driver education efforts 

and the reduction of WVCs. 
 76 

Figure 31. Photo. Poster produced by the Maine Department of Transportation (source: 

Maine Department of Transportation). 
 77 

Indirect Benefits 

Many driver education and public information campaigns summarize and display crash data 

maps related to WVCs. This spatial information can also be used for focusing limited resources 

to roadside mitigation methods for the most problematic areas within a state, county, or 

metropolitan area. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

For statewide public information campaigns, costs were low compared to other mitigation 

methods. Maine has spent about $6,500 for its moose and deer crash maps and moose safety 

brochures. This investment provided an adequate outreach supply to last for about three years 

(Duane Brunell, Maine Department of Transportation, personal communication). In Colorado, 

the “Wildlife on the Move” Campaign cost $16,335. Most expenses were in two categories: 

(1) printing of publications (a little more than $10,000) and (2) contract labor for outreach (a 

little more than $4,500) (Monique DiGiorgio, Southern Rockies Ecosystem Project, personal 

communication). Costs for the Don’t Veer for Deer campaign in Iowa were negligible (Michael 

Pawlovich, Iowa Department of Transportation, personal comment). 

Guidelines 

Given that drivers are open to receiving more educational information to help reduce WVCs, it 

may be most cost effective to focus driver education and public information efforts toward 18- to 

45-year-olds, as they are involved in the highest numbers of AVCs (see figure 32). In a study in 

Kent County, MI, registered drivers between the ages of 30 and 39 had the highest number of 

DVCs.(181) If public campaigns or local education programs can be focused for specific age 

groups, 30- to 45-year-olds should be targeted. Note that figure 32 also suggests that drivers do 

not benefit from driving experience where AVCs are concerned. Campaigns directed at younger 

drivers, who have higher AVC crash rates, may also be studied. 
 78 

0

0.01

0.02

0.03

0.04

0.05

1 11 21 31 41 51 61 71 81 91

Driver Age

Proportion of Collisions

All

AVC

Figure 32. Graph. Driver age distribution for all crashes and AVCs (HSIS data). 

ROADWAY WARNING SIGNS 

Roadway wildlife warning signs are perhaps the most commonly applied WVC mitigation 

measure.(85,182) The signs alert the drivers to the potential presence of wildlife on or near the road 

and urge them to be more alert, to reduce the speed of their vehicle, or a combination of both. 

These signs attempt to prevent a collision or to reduce the severity of a collision if one does 

occur by lowering vehicle speeds at impact (figure 33). 

Since the effectiveness of warning signs depends on driver response, it is critical that warning 

signs are reliable (i.e., the driver is warned when there is a high chance of WVC). The warning 

signs discussed below (standard warning signs, large or enhanced warning signs, seasonal 

wildlife warning signs, and animal detection systems) should be placed in road sections that 

exceed a certain minimum risk of WVC. The current location selection process can typically be 

improved upon.(53,183,184) Seasonal wildlife warning signs need to be in place during those periods 

of the year that animals cross the road most frequently. Animal detection systems (if used) need 

to be connected to reliable sensors used for the detection of large animals on or near the road. 
 79 

Figure 33. Flow chart. Warning signs and driver response. 

Driver awareness and response are influenced by the type of warning sign.(185,186,187) Large and 

graphic signs, flags attached to wildlife warning signs, permanently flashing lights on top of or 

around wildlife warning signs, and messages displayed on variable message signs are designed to 

attract the attention of the driver and invoke response to a greater extent than standard wildlife 

warning signs. Seasonal wildlife warning signs are designed to deliver a more time specific 

warning message to drivers; they are only displayed during certain times of the year when the 

risk is much higher, for example during the seasonal migration of certain species. Animal 

detection systems are even more time specific in their operation; the warning signals are only 

activated after a large animal has been detected on or near the road. 

Driver response is split into two components: increased alertness and lower vehicle speed. 

Increased alertness can lead to a reduction in driver reaction time. Driver reaction time to an 

unusual and unexpected event can be reduced from 1.5 s to 0.7 s if drivers are warned.(188)

Assuming a constant vehicle speed of 88 km/h (55 mi/h) before and after warning signals have 

been presented to a driver, increased driver alertness could reduce the stopping distance of the 

vehicle by 21 m (68 ft). This reduction in reaction time and stopping distance, however, has not 

been specifically tested with respect to the presence of large animals in rural areas, let alone for 

warning signals that may apply to road sections of many miles rather than a point or short road 

section. Lower vehicle speed allows for more reaction time, and should a collision still happen, it 

is likely to be less severe.(189) At relatively high speed even small reductions in vehicle speed 

matter because the relation between vehicle speed and the risk of a severe accident is 

exponential; small reductions in vehicle speed result in a disproportionate decrease in the risk of 

a severe accident.(189) 
 80 

STANDARD WILDLIFE WARNING SIGNS 

The standard deer warning sign in the United States is a diamond-shaped panel with a black deer 

symbol on a yellow background, sometimes accompanied by text signs that indicate the length of 

the road section to which the sign applies (figure 34). 

Figure 34. Photo. Standard deer warning sign along Montana Highway 83 

(copyright: Marcel Huijser, WTI). 

Meyer investigated the effectiveness of standard deer warning signs in Kansas by comparing the 

accident data before and after sign installation.(190) After taking all available accident data before 

sign installation and other road and landscape parameters into consideration, there was no 

evidence that the presence of the deer warning signs had resulted in fewer DVCs.(190) Rogers also 

concluded that the number of DVCs had not reduced as the result of the installation of deer 

warning signs.(38) Furthermore, the installation of standard camel crossing signs in Saudi Arabia 

did not result in reduced vehicle speed.(191) Finally, in a driving simulator study, a standard deer 

warning sign resulted in an average vehicle speed of 123.2 km/h (76.6 mi/h), just over the posted 

speed limit of 120.7 km/h (75 mi/h).(192) This result shows that a standard deer warning sign was 

unable to reduce the average vehicle speed to the posted speed limit or lower. 

Case Studies and Contacts 

For information about the study on the effectiveness of deer warning signs in Kansas, contact: 

Eric Meyer, University of Kansas, Civil, Environmental & Architectural Engineering 

Department, 1530 West 15th Street, Room 2150, Lawrence, KS 66045-7609 (he is currently 

affiliated with Meyer Intelligent Transportation Services, (785) 843-

2718, emeyer@insighthawks.com). 
 81 

Direct Benefits 

Based on the available data, standard deer warning signs are concluded to be ineffective in 

reducing WVCs, in general, and DVCs, in specific. 

Most authors doubt the effectiveness of standard warning signs, but only two studies were found 

that had investigated the effectiveness, confirming the existing doubts. (See references 9, 38, 58, 

182, 185, 190, and 193.) 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

As a general rule, unnecessary signs should be removed as they may distract drivers and require 

maintenance. However, standard warning signs may be required to reduce liability in case of 

WVCs.(194) 

Costs 

One study estimated costs at $94 (note not adjusted for inflation) per sign.(185) USA Traffic Signs 

reports the following costs: $55 (61 by 61 cm (24 by 24 inches)), $62 (76 by 76 cm (30 by 

30 inches)), $85 (91 by 91 cm (36 by 36 inches)).(195) 

Guidelines 

The Manual on Uniform Traffic Control Devices (MUTCD) provides guidance on animal 

warning signs. The standard warning sign (figure 34) is known as W11-3. The MUTCD is very 

specific in the sign dimensions, colors, etc. However, the manual only provides general guidance 

on when to use these signs: 

“Nonvehicular signs [this includes animal warning signs] may be used to alert 

road users in advance of locations where unexpected entries into the roadway or 

shared use of the roadway by pedestrians, animals, and other crossing activities 

might occur.”(196) 

See Knapp and Yi for a discussion on guidelines for the installation of standard deer warning 

signs.(183) 

LARGE, NONSTANDARD WILDLIFE WARNING SIGNS 

Large or enhanced animal warning signs may take many forms. They can be larger than the 

standard wildlife warning signs, include graphic images of a vehicle hitting wildlife, and have 

permanently activated flashing amber warning lights, light emitting diodes (LEDs), or red flags 

attached to the signs (figure 35 and figure 36). 
 82 

Figure 35. Photo. Large enhanced warning sign for bighorn sheep along State Highway 75 

in Idaho (copyright: Marcel Huijser, WTI). 

Lighted animated deer crossing signs reduced vehicle speed by 4.8 km/h (3.0 mi/h) compared to 

the same signs when they were turned off.(185) The presence of deer carcasses as a “supplement” 

to the signs resulted in a much greater reduction in vehicle speed: 12.6 km/h (7.9 mi/h) (lights 

turned off) and 10.0 km/h (6.2 mi/h) (lights turned on).(185) Despite the successful speed 

reduction of the lighted animated signs, they did not result in a reduction of DVCs.(185) 

Hammond and Wade conducted an experiment in a driving simulator and exposed drivers to 

standard deer warning signs and enhanced deer warning signs that had a flashing light on top of a 

standard deer warning sign.(187) The average vehicle speed with standard deer warning signs was 

99.6 km/h (61.87 mi/h) (SD = 5.16). The enhanced sign with the lights turned off resulted in 

similar speeds of 99.5 km/h (61.80 mi/h) (SD = 4.80), but the enhanced sign with the lights 

turned on resulted in significantly lower vehicle speed of 95.9 km/h (59.55 mi/h) (SD = 4.66), a 

reduction of 3.7 km/h (2.32 mi/h).(187) 
 83 

Figure 36. Photo. Large enhanced elk warning sign along the Trans-Canada Highway in 

Banff National Park, Canada (copyright: Marcel Huijser, WTI). 

Enhanced camel warning signs in Saudi Arabia resulted in a significant reduction of vehicle 

speed whereas standard camel warning signs did not.(191) The standard warning signs were 

triangular where all sides were 110 cm (43 inches), with a red border and white interior with 

black camel silhouette, and did not have diamond reflective material. The enhanced signs were 

signs that were larger than the standard warning signs, had diamond reflective material, had a 

yellow camel on a black background, and/or were accompanied by the text message “camelcrossing” and a reduced advisory speed limit. The enhanced signs reduced vehicle speed by 

3–7 km/h (2–4 mi/h).(191) 

Hardy and others found that wildlife advisory messages posted on permanent and portable 

dynamic message signs (DMS) can reduce vehicle speeds.(173) The greatest effect occurred 

during “dark” conditions, when the number of AVCs is higher. 

Stanley and others conducted experiments with a driving simulator and found that enhanced 

wildlife warning signs resulted in lower vehicle speeds and earlier braking when drivers were 

confronted with a deer in the simulated environment.(192) 

Case Studies and Contacts 

For information about a driving simulator study with enhanced deer warning signs, contact 

Curtis Hammond and Michael G. Wade, University of Minnesota, Division of Kinesiology, 

1900 University Ave SE, Minneapolis, MN 55455; (612) 625-2051, chammond@umn.edu; 

(612) 626-2094, mwade@umn.edu. 

For more information about a field test with enhanced camel warning signs in Saudi Arabia, 

contact Ali Al-Ghamdi and Saad AlGadhi, Civil Engineering Department, College of 
 84 

Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia, 

+966-1-4677019, (fax +966-1-4673366), asghamdi@ksu.edu.sa. 

For information about wildlife advisory messages posted on permanent and portable DMS, 

contact Amanda Hardy, Western Transportation Institute, (406) 994-

2322, ahardy@coe.montana.edu. 

For information about a driving simulator study with enhanced deer warning signs, contact Laura 

Stanley, Virginia Polytechnic Institute & State University, Blacksburg, VA 24060, 

(540) 808-5140, lstanley@vtti.vt.edu. 

Direct Benefits 

The only study identified that directly looked at sign impact on WVCs, rather than the impact on 

driver response, suggests that large or enhanced wildlife warning signs are not effective in 

reducing WVCs in general or DVCs specifically.(185) Nonetheless, the observed reduction in 

vehicle speed (3–7 km/h (2–4 mi/h)) suggests that the signs may be somewhat effective after all, 

perhaps reducing the severity of the crash in terms of property damage, human injuries and 

human fatalities. Only limited data are available on this subject. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

Uniform warning signs across the United States are desirable so that drivers learn and understand 

what different signs represent (known as “driver expectancy”). While nonstandard signs may 

draw attention, a potential downside is that it takes drivers longer to interpret the sign, simply 

because it is nonstandard. 

Costs 

One cost estimate reported in the literature was $2,000 (note: not adjusted for inflation) per 

sign.(185) 

Guidelines 

It should be noted that many nonstandard animal warning signs deviate from the MUTCD. 

Although some states have adopted alternative signs into their state manual on traffic control, 

care should be taken when the MUTCD is not followed exactly. It may degrade driver 

expectancy and could open the State DOT to liability issues. 

See Knapp and Yi for a discussion of guidelines for the installation of nonstandard deer warning 

signs.(183) 
 85 

SEASONAL WILDLIFE WARNING SIGNS 

Seasonal wildlife warning signs are only present at certain times of the year when animals cross 

the road most frequently, such as during a seasonal migration (figure 37). 

Figure 37. Photo. Seasonal deer migration sign in Utah (copyright: Marcel Huijser). 

Sullivan and others erected temporary warning signs with (1) reflective flags and 

(2) permanently flashing amber lights in locations that were known to be used by mule deer 

(Odocoileus hemionus) during their seasonal migration.(43) The number of DVCs was reduced by 

51 percent (range 41.5–58.6 percent for individual test areas) compared to control areas. The 

signs reduced the percentage of speeders from 19 percent to 8 percent during their first season of 

operation, but the effect was less pronounced in the second season, perhaps due to driver 

habituation.(43) 

Rogers investigated the effect of enhanced deer warning signs (black on yellow sign showing a 

deer and a car symbol, combined with a black on orange sign stating “HIGH CRASH AREA”) 

on the number of DVCs.(38) The signs were deployed between October and January (the peak of 

DVCs) for three consecutive years. Rogers found no effect of the seasonal signs on the number 

of DVCs.(38) 

Case Studies and Contacts 

For information about a field study on the effectiveness of seasonal warning signs in Utah, 

Nevada and Idaho, contact Todd L. Sullivan, Jack H. Berry Institute, Department of Forest, 

Range and Wildlife Sciences, Utah State University, Logan, UT. (Current address: 

USDA/APHIS Wildlife Services, 5107 Austin Ellipse, Moody Air Force Base, GA 31699). 
 86 

Direct Benefits 

Seasonal deer warning signs may reduce DVCs; however, more studies on their effectiveness are 

required. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

The signs reportedly are subject to vandalism and theft.(43) 

Costs 

Sullivan and others reported a cost of $268 per 1,609 m ($435 per mi).(43)

Guidelines 

See Knapp and Yi for a discussion of guidelines for the installation of seasonal deer warning 

signs.(183) 

ANIMAL DETECTION SYSTEMS 

Animal detection systems use sensors to detect large animals that approach the road. Once a 

large animal is detected, warning signals are activated to inform the drivers that a large animal 

may be on or near the road at that time (figure 38). The warning signals are extremely time 

specific. Huijser and others listed more than 30 locations in North America and Europe that have 

had an animal detection system installed, and they describe the experiences with installation, 

operation and maintenance, reliability, and effectiveness.(197) Since August 2007, a number of 

additional locations were equipped with an animal detection system, including along SR 260 

near Payson, AZ (David Bryson, Electrobraid Fence Ltd., personal communication; Norris Dodd, 

Arizona Game and Fish Department, personal communication). An animal detection system 

combined with electric fencing was used at these locations. 
 87 

Figure 38. Photo. Animal detection system along Highway 191 in Yellowstone National 

Park, MT (copyright: Marcel Huijser, WTI). 

Two broad categories are commonly used in animal detection systems: area-cover systems and 

break-the-beam systems. Area-cover systems detect large animals within a certain range of a 

sensor. Area-cover systems can be passive or active. Passive systems detect animals by only 

receiving signals. The two most common systems are passive infrared and video detection. These 

systems require algorithms that distinguish between, e.g., moving vehicles with warm engines 

and moving pockets of hot air and movements of large animals. Active systems send a signal 

over an area and measure its reflection. The primary active area-cover system is microwave 

radar. Break-the-beam sensors detect large animals when their body blocks or reduces a beam of 

infrared, laser, or microwave radio signals sent by a transmitter to a receiver. Other less common 

detection systems include a system that depends on radio-collared animals and receivers placed 

in the right of way, and a system that uses seismic sensors to detect vibrations in the soil as large 
 88 

animals approach.(197) Most of these systems have or had problems with the reliability of the 

sensors, although some of the manufacturers seem to have overcome these problems.(197) 

The effectiveness of animal detection systems has been investigated with regard to a potential 

reduction in vehicle speed and a potential reduction in AVCs. Once a driver is aware that a large 

animal may be on or near the road ahead, the driver may lower the speed of the vehicle. Previous 

studies have shown variable results: substantial decreases in vehicle speed (greater than or equal 

to 5 km/h (3.1 mi/h)), minor decreases in vehicle speed (less than 5 km/h (3.1 mi/h)), and no 

decrease or even an increase in vehicle speed. (See references 42, 187, 198, 199, 200, and 201.) 

This variability of the results appears to be related to various conditions, namely, type of warning 

signal and signs, whether the warning signs are accompanied with advisory or mandatory speed 

limit reductions, road and weather conditions, whether the driver is a local resident, and perhaps 

also cultural differences that may cause drivers to respond differently to warning signals in 

different regions.(197) 

Kistler, Romer and Mosler-Berger, and Mosler-Berger and Romer have reported on the number 

of AVCs before and after seven infrared area-cover detection systems were installed in 

Switzerland (table 8). (See references 198, 202, 203, and 204.) These systems reduced the 

number of AVCs by 82 percent on average (1-sided Wilcoxon matched-pairs signed-ranks test, 

P = 0.008, n = 7).(197) All seven sites showed a reduction in collisions after an animal detection 

system was installed, and three of the seven sites did not have a single collision after system 

installation (as of 6–7 years after installation). The data relate to collisions with roe deer 

(Capreolus capreolus) and red deer (Cervus elaphus), and collisions that occurred during the day 

when the systems were not active were excluded from the analyses. 

While the data on the effectiveness of animal detection systems are encouraging, animal 

detection systems should still be regarded as an experimental mitigation measure rather than a 

measure that will reduce WVCs on short term with a high degree of certainty.(197) 

Table 8. Collisions with large animals before and after detection system installation in 

Switzerland. 

Location 

Before Installation After Installation Reduction 

Coll. 

(N) Yrs. Coll./yr 

Coll. 

(N) Yrs. Coll./yr Coll./yr % 

Warth 14 7 2.00 3 10 0.30 1.70 85.00 

Soolsteg 8 11 0.73 1 6 0.17 0.56 77.08 

Val Maliens 7 3 2.33 6 5 1.20 1.13 48.57 

Marcau 12 4 3.00 6 5 1.20 1.80 60.00 

Schafrein 26 8 3.25 0 6 0.00 3.25 100.00 

Duftbächli 18 8 2.25 0 6 0.00 2.25 100.00 

Grünenwald 6 8 0.75 0 7 0.00 0.75 100.00 

Average Reduction 81.52 
 89 

Case Studies and Contacts 

For a general overview of technology, reliability and effectiveness, contact Marcel Huijser, 

Western Transportation Institute, P.O. Box 174250, Bozeman, MT 59717-4250, (406) 543-2377, 

mhuijser@coe.montana.edu. 

For information about a field study on the effectiveness of animal detection systems, contact 

Christa Mosler-Berger, Wildtier Schweiz, Strickhofstrasse 39, 8057 Zürich, 

Switzerland, wild@wild.unizh.ch. 

For more information about the animal detection system and wildlife fencing along State Route 

260 in Arizona, contact Norris Dodd, Wildlife Research Biologist, Arizona Game and Fish 

Department, Research Branch, P.O. Box 2326, Pinetop, AZ 85935, (928) 368-5675, 

doddnbenda@cybertails.com. 

Manufacturer: Terry Wilson, Sensor Technologies and Systems, Inc., 8900 East Chaparral Road 

Scottsdale, AZ 85250, (480) 483-1997, (fax (480) 483-2011), terry_wilson@sensortech.com, http://www.sensor-tech.com/ (accessed January 25, 2007). 

Manufacturer: Calonder Energy AG’s representative in USA: Willy Bärchtold, Swiss Army 

Vehicles, 1436 Van Asche Drive, Fayetteville, AR 72704, (479) 521-0056, cars@sav.ms. 

Direct Benefits 

The only available data on the effectiveness of animal detection systems show a reduction in 

collisions with large animals of 82 percent.(197) This percentage may change as more data 

become available. 

Indirect Benefits 

Animal detection systems do not restrict animal movements when deployed over long distances. 

Undesirable Effects 

Animal detection systems can reduce collisions with large animals, but the presence of poles and 

equipment in the right of way is a potential hazard to vehicles that run off the road.(197) 

Costs 

Estimated costs of these systems are $40,000–96,000 per km ($65,000–154,000 per mi) 

(excluding installation costs) (unpublished data, Marcel Huijser, Western Transportation 

Institute, Montana State University).(197) The costs for the equipment will be higher if the road 

section concerned has curves or slopes, or if the line of sight in the right of way is blocked by 

objects. 
 90 

Guidelines 

It should be noted that many animal detection systems use signs that deviate from the MUTCD. 

Some states have adopted alternative signs into their state manual on traffic control. Care should 

be taken when the MUTCD is not followed exactly. It may degrade driver expectancy and could 

open the State DOT to liability issues. 

See Huijser and others for considerations for planning and design.(197) 

IN-VEHICLE WARNINGS: ROADSIDE ANIMAL DETECTION SYSTEM LINKED TO 

ON-BOARD COMPUTER WARNING SYSTEM 

The concept of an animal detection system that is linked to an on-board computer warning 

system is described in Huijser and others.(197) The technology would be designed to warn a driver 

through a warning signal inside the vehicle that an animal is on or near the roadway within a 

certain distance from the vehicle. This technology is not currently deployed. This information 

should be provided just before drivers get to the area covered by the animal detection system. 

Road signs and highway advisory radio messages are the most obvious ways to deliver this 

information to the driver. When approaching the animal detection system, a driver may be 

confronted with an activated warning signal indicating that a large animal has been detected and 

is present on or near the road at that time. In the future the information about the purpose and the 

location of the animal detection system may also be delivered to an on-board computer inside the 

vehicle. This procedure would require a two-way GPS-based communication system. The most 

essential part of the concept is that the warning signal from the animal detection system is 

delivered to the on-board computer as soon as the vehicle gets within a certain radius of the 

animal detection system and if a large animal has been detected. 

Case Studies and Contacts 

No case studies and contacts are available, as this technology has not yet been deployed. 

Direct Benefits 

This mitigation measure has not been specifically investigated. However, the effectiveness can 

be expected to be similar to that of animal detection systems, i.e., 82 percent reduction in 

collisions with large animals.(197) This percentage is likely to change as data become available. 

Indirect Benefits 

Animal detection systems do not restrict animal movements when deployed over long distances. 

Undesirable Effects 

Animal detection systems can reduce collisions with large animals, but the presence of poles and 

equipment in the right of way is a potential hazard to vehicles that run off the road.(197) 
 91 

Costs 

Estimated costs for these systems are $40,000–96,000 per km ($65,000–154,000 per mi) 

(excluding installation costs), plus additional costs for the on-board computer and 

communication system (Marcel Huijser, unpublished data, Western Transportation Institute, 

Montana State University).(197) The costs for the equipment will be higher if the road section 

concerned has curves or slopes, or if the line of sight in the right of way is blocked by objects. 

Guidelines 

See Huijser and others for considerations for planning and design.(197) 

IN-VEHICLE WARNINGS: ON-BOARD ANIMAL DETECTORS 

On-board animal detectors (typically infrared detectors) inform drivers when a large animal (or 

human being) is detected within a certain range from the sensors attached to the vehicle. (See 

references 205, 206, 207, and 208.) The range should be sufficient to allow for the driver to stop 

the vehicle before impacting the detected animal. The system could potentially detect large 

animals anywhere; it would not depend on the installation of any roadside equipment. However, 

it is uncertain whether these on-board detectors are still in production. 

Case Studies and Contacts 

For design concept, contact Masaki Hirota, Nissan Motor Co., Ltd., 1 Natsushima-cho, 

Yokosuka Kanagawa 237-8523, Japan, m-hirota@mail.nissan.co.jp. 

Direct Benefits 

Because this concept is still in the design phase, no direct benefits were identified in the 

literature review. However, the benefits would be expected to be similar to animal detection 

systems. 

Indirect Benefits 

The system would not only detect large animals but potentially also humans (e.g., pedestrians, 

bicyclists). 

Undesirable Effects 

Vehicle-based systems only inform drivers in vehicles equipped with such a detection system. 

Drivers in other vehicles will not benefit. 

Costs 

A reported cost for these detectors is $2,250 per vehicle.(53) 

Guidelines 

See Hirota and others for design concept.(207) 
 92 

INCREASE VISIBILITY OF ANIMALS TO DRIVERS 

A driver’s ability to avoid a collision with an animal may be determined in a split second. Once 

drivers see a road hazard, it may take 0.7 to 1.5 s (depending on whether the hazard was 

anticipated or unexpected) to move their foot from the accelerator to the brake.(188) Depending on 

vehicle speed and when an animal crossing the road is first seen, a collision may occur before the 

driver even has the chance to brake. The sooner drivers see an animal in the road, the better their 

chances of responding quickly to avoid a collision. Roadway lighting and vegetation removal 

have been used in an attempt to increase visibility to provide as much time and space possible for 

drivers to see and respond to animals in or near the roadway. 

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: ROADWAY LIGHTING 

Most WVCs occur between dusk and dawn when light, and thus visibility, is limited (see Section 

on Causes and Factors of WVCs: Temporal Distributions). (See references 9, 10, 38, 75, 78, 79, 

209, 210, and 211.) The drab coloring of most wildlife species increases the probability that a 

driver may not see an animal in the dark. Even the most attentive driver would have difficulty 

seeing a dark-colored moose on a dark road at night in time to avoid a collision. Garrett and 

Conway characterized moose-vehicle collision occurrences in Anchorage, AK, finding these 

incidents were 2.6 times more likely to occur during periods of darkness; further, 61 percent of 

collisions that occurred during dark periods occurred where there were no streetlights 

illuminating the road.(79) Lavsund and Sandegren found the risk of moose-vehicle collisions in 

Sweden was six times higher during hours of darkness compared to daylight conditions.(76) It has 

been hypothesized but not well documented that lighting may help drivers see animals and avoid 

such collisions in nondaylight hours. 

Numerous reviews of WVC mitigation measures mention use of roadway lighting in attempts to 

reduce WVCs. (See references 3, 9, 68, 74, 176, 212, 213, 214, 215, and 216.) Most of these 

reviews either do not provide support that highway lighting is effective or conclude that highway 

lighting is ineffective. Reed and Woodard found that highway lighting was not effective in 

reducing DVCs in Colorado.(217) L-P Tardiff and Associates, Inc. cited a study by Miller 

indicating that lighting was ineffective for mitigating WVCs (no further information was 

provided and the report was unavailable at the time that this review was drafted).(68,218)

Alternatively, one review states, “Lighting has been used on numerous occasions and has been 

shown to be effective in high crash locations because it gives drivers a longer reaction time” but 

does not cite any specific studies to support that claim.(215) Knapp classifies the use of roadway 

lighting as a method that is “not generally used and rarely studied for safety impacts” and cites 

that the American Association of State Highway Transportation Officials regard this measure as 

“experimental.”(176) 

Despite discrepancies in the tested effectiveness of highway lighting, the practice of using 

highway lighting has been recommended in certain situations. Garrett and Conway recommend 

the installation of streetlights, encouraging drivers to upgrade older vehicles’ headlights with 

halogen bulbs, and keeping the lenses of the lights free of dirt and debris to increase the chance 

of seeing a moose in time to avoid a collision.(79) Thomas also suggests that roadway lighting be 

considered for reducing moose-vehicle collisions in Alaska.(78) 
 93 

Given the paucity of information on the efficacy of lighting to reduce WVCs, there is a need to 

further explore the usefulness of this approach. If recommendations to install lighting are 

pursued, quantitative studies with experimental designs should be employed to further 

understand the effect that lighting and increased visibility may have on WVCs. 

Reed and Woodard conducted a five-year study in Colorado that involved alternately turning 

roadside lights on and off for one-week periods to quantify the effect on DVCs, observed deer 

crossings of the highway at night, and vehicle speeds.(217) Lighting did not affect DVCs or driver 

speeds; however, drivers did significantly reduce speeds when a deer decoy was present (this 

practice was discontinued due to concerns about abrupt driver responses to the decoy, creating a 

potential safety concern for other motorists). Lighting did not disrupt deer crossing behaviors, 

although it appeared that a greater proportion of deer crossed in the lighted areas compared to 

prior to the study and when the lights were off. 

A four-year study of the installation of roadway lighting, fencing, one-way gates and bridge 

modifications along 11.5 km (7.1 mi) of the Glenn Highway near Anchorage, AK, revealed a 

70 percent decrease in moose-vehicle collisions overall.(213,219,220) The entire area was lighted, 

while about 5.5 km (3.4 mi) of the road had fencing, one-way gates, and modified bridges. The 

lighted area with fences reduced moose-vehicle collisions by 95 percent, while the areas with 

lighting but without fencing reduced moose-vehicle collisions by 65 percent. However, it was 

not clear if the 65 percent reduction in moose collisions was the result of moose avoiding the 

lighted areas or the result of increased motorist visibility.(213,219,220) 

Case Studies and Contacts 

For information about roadway lighting and fencing to reduce WVCs, contact Biota Research 

and Consulting, Inc., info@biotaresearch.com. 

Direct Benefits 

Reduction of moose-vehicle collisions by 65 percent was found in Alaska, but it is not clear if 

this was due to increased visibility or moose avoiding the lighted area. 

Indirect Benefits 

Griffith found that highway lighting reduced all “property damage only” (i.e., no human injury) 

crashes at night.(221) The typical method for comparisons for before/after installation is a 

reduction in the ratio of nighttime crash rates to daytime crash rates. Griffith found this ratio 

reduced by 32 percent for all property damage only crashes. However there was no reduction in 

injury or fatal crashes. 

Undesirable Effects 

An undesirable effect of roadway lighting is the impact on a driver’s vision after leaving the 

lighted area. While driving through the lighted area, a driver’s eyes will become accustomed to 

the light. Afterward, it may take some time before the driver’s eyes readjust to less light. 
 94 

Some sensitive species (e.g., Canada lynx, mountain lions (Felis concolor), bears, and gray 

wolves (Canis lupus) may avoid light, which may result in an unintentional barrier effect for 

lighted areas.(222) In addition, roadway lighting may temporarily blind certain species as their 

eyes are adapted to darkness, potentially increasing their vulnerability to traffic.(212) 

Costs 

Mode and others noted that in 2001, $1.3 million was dedicated to lighting three miles of the 

Glenn Highway in Alaska to improve motorist visibility of moose.(223) Hedlund and others state 

that roadway lighting is expensive but did not provide any figures to illustrate the estimated 

expense.(214) L-P Tardiff and Associates, Inc. mention Miller’s report, which states that highway 

lighting is expensive, but again, no figures accompanied that statement.(68,218) 

Guidelines 

For guidelines on highway lighting, refer to the Roadway Lighting Handbook and 

Addendum.(224,225) 

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: VEGETATION REMOVAL 

Visibility may be improved by reducing roadside vegetation that may obscure wildlife 

approaching the road. In a study of DVC mortalities in east central South Dakota, Gleason and 

Jenks found that deer were killed more often than expected in areas adjacent to shelterbelts with 

canopy vegetation.(226) Puglisi and others found that DVC occurrences were less common where 

wooded areas were more than 23 m (25 yds) away from a highway in Pennsylvania.(32) 

Clearing vegetation from roadsides resulted in a 20-percent reduction in moose-vehicle collisions 

in Sweden.(76) In a study examining the effect of scent marking, intercept feeding and forest 

clearing, analyses demonstrated that forest clearing resulted in a 49-percent reduction in 

collisions.(227) While it is recognized that the results may not translate to a highway setting, the 

clearing of vegetation across a 20- to 30-m (70- to -100-ft) swath on each side of a Norwegian 

railway reduced moose-train collisions by 56 percent (+/-16 percent).(228) 

Thomas states that vegetation clearing is one of the most commonly applied measures to reduce 

moose-vehicle collisions; recommendations from that report include that vegetation clearing 

should be applied in an effort to reduce moose-vehicle collisions in Alaska.(78) Distance between 

the roadway and forest cover has been shown to be negatively correlated to DVCs in Illinois; 

recommendations from that study included removing vegetation to provide an open width of the 

road corridor of at least 40 m (131 ft) in areas where DVCs are particularly high.(30) Based on 

results from predictive models, Seiler notes that moose-vehicle collisions in Sweden were more 

common on roads that cross through clear cuts and young forests and suggests collisions with 

moose may be reduced by 15 percent in areas where the distance between forest cover and the 

road exceeds 100 m (300 ft).(25) 

In addition to affecting visibility, roadside vegetation management may be directed to reducing 

the attractiveness of roadside forage to animals. While vegetation management to increase 

visibility and reduce the draw of animals to the right of way may be complementary goals in 
 95 

some cases, Putman and others summarize the potentially conflicting outcomes of reducing 

vegetation along roadways: 

“The management of roadside vegetation—and specifically, the clearance of woodland or scrub 

from a margin at the road edge—may have benefits both in increasing driver awareness of deer 

at the roadside, and increasing visibility of oncoming traffic to the deer themselves. In addition, 

removal of such vegetation and the cover that it provides may also reduce the probability of deer 

approaching so close to the road edge in the first place. The method and timing of removal of 

such vegetation may however be critical. While the removal of vegetation within transportation 

corridors may help improve driver and animal visibility, simple cutting of encroaching shrub and 

tree growth may at the same time increase the subsequent attractiveness of these cut-over areas 

as foraging sites by deer. Such measures might thus actually result in an increase in the number 

of deer utilizing the roadside—ultimately increasing the risk of accident.”(58) 

For further discussion of vegetation issues, see also the section titled “Influence Species 

Composition or Minimize Nutritional Value of Vegetation in Right of Way” in chapter 6. 

Case Studies and Contacts 

No contacts for this mitigation measure were identified in the literature review. 

Direct Benefits 

Jaren et al. and others conducted an eight-year study of the effect of vegetation removal on 

moose-train collisions in Norway and found that clearing vegetation across a 20- to 30-m (70- to 

100-ft) swath on each side of the railway reduced moose-train collisions by 56 percent (+/-16 

percent).(228) Lavsund and Sandegren showed that clearing of vegetation along transportation 

corridors resulted in a 20-percent reduction in moose-vehicle collisions in Sweden.(76) 

Indirect Benefits 

Reducing the number of large trees near roads may result in fewer collisions with these 

stationary obstructions.(214) 

Undesirable Effects 

Removal of brushy species of vegetation or canopy may result in fresh growth of attractive 

forage that draws grazing animals to the right of way, potentially counteracting the potential 

safety gains of better visibility with increased probability of drivers encountering wildlife.(74) 

Costs 

Vegetation removal requires long-term maintenance commitment and may involve expenses to 

acquire right of way in order to manage vegetation as desired. Jaren and others calculated that if 

collisions are reduced by at least 50 percent as a result of removing vegetation, then the costs of 

vegetation removal treatment would be economically beneficial if applied in areas where more 

than 0.3 per km (0.48 per mi) moose-train collisions occur.(228) Andreassen and others estimate 

forest clearing for 18 km (11.2 mi) costs $500 per km ($800 per mi) or $9,000 per year, showing 
 96 

that the number of moose saved using this technique could result in a profit of $1,080.(227)

Andreassen and others state that forest clearing may be more economical compared to scent 

marking and supplemental feeding, stating that the initial cutting is the main expense.(227) 

Guidelines 

Thomas provides a summary of a variety of vegetation clearing methods used in Alaska 

including hydroaxing, hand clearing, steam clearing, and spray inhibitors.(78) 

The timing and effect of vegetation clearing depends on the vegetation and climate at the 

roadway site and needs to be carefully evaluated. 

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: WIDER STRIPING 

Drivers may see a break in the painted highway striping (particularly if it is wide) when an 

animal crosses it, even if the animal itself is difficult to distinguish due to color, background, or 

lighting conditions, and thus be warned of its presence on the highway. In addition, wide striping 

may make the driver perceive a narrower roadway, potentially resulting in lower vehicle speed 

(see later section on traffic calming and reducing design speed). 

Wide striping was used along Rt. 4 in Phillips, ME, and along Rt. 6/15 in Shirley, ME.(229) The 

Rt. 6/15 road section in Shirley also had temporary optical markers (TOMs) installed. TOMs are 

small yellow reflective tags which are typically used as a substitute for striping during roadway 

construction activities. When a large animal, e.g., a moose, enters the roadway, the absence of 

light reflecting off the TOMs obstructed by the animal may result in a visual break for drivers, 

and thus a warning.(229) No evaluation or results of these installations were found. 

Case Studies and Contacts 

Contacts for the case studies mentioned above could not be identified. 

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

No costs were identified in the literature review. 
 97 

Guidelines 

No guidelines were identified in the literature review. 

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: REFLECTIVE COLLARS FOR 

ANIMALS 

One of the mitigation measures under consideration at a location in Canada is to put collars with 

reflective tape on a number of animals to increase their visibility to drivers. Free ranging wood 

bison (Bos bison) were reintroduced in northeast British Columbia. Their number has grown to 

about 100 individuals. The bison spend about 90 percent of their time on or near a 150-km 

(31-mi)-long section of the Alaska Highway near the Yukon border because of the attractive 

vegetation in the right of way and because the disturbance associated with the right of way may 

provide a shelter from predators. They are typically found in large groups, and a number of 

serious bison-vehicle collisions have taken place. 

Case Studies and Contacts 

For information about the proposal to put collars with reflective tape on bison, contact Conrad 

Thiessen, Wildlife Biologist, Peace Region, Ministry of Environment, 400-10003 110 Ave., 

Fort St. John, British Columbia, V1J 6M7 Canada, phone: (250) 787-3287, fax: (250) 787-

3490, Conrad.Thiessen@gov.bc.ca

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

It requires considerable and continuous effort to have a certain minimum number of bison (or 

any other species, including deer) equipped with collars with reflective tape. In addition, 

capturing and handling activities are likely to cause stress and risk of injury and death for the 

animals involved. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 
 98 

INCREASE VISIBILITY OF ANIMALS TO DRIVERS: REDUCE HEIGHT OF 

SNOWBANKS 

Garrett and Conway suggested reducing the height of snow berms in order to increase drivers’ 

visibility of moose on the side of the road.(79) They acknowledge this practice would be 

impractical and expensive to employ on all streets, and thus this might be better applied in 

particular areas with high rates of moose-vehicle collisions. 

Case Studies and Contacts 

No contacts were identified in the literature review. 

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 

REDUCE TRAFFIC VOLUME ON ROAD NETWORK 

The increase in the number of WVCs (chapter 2) is associated with factors such as new highway 

construction, increased traffic volumes and speeds, wildlife population distribution, and wildlife 

abundance.(58,230) As mentioned in chapter 2 in the section titled “Is the Problem Growing,” the 

average crash rate (number of crashes per vehicle mile traveled) has held fairly constant for 

WVCs; but the total number of VMT and thus the total WVCs have increased. The relationship 

between the number of WVCs and traffic volume on a single roadway, however, is confounded 

by changes or differences in wildlife population size and relatively great data variability.(74) 

No original studies were located that tested the effectiveness of permanently lowering traffic 

volume on highways or permanently lowering road density of paved roads as a mitigation 

measure for reducing WVCs. Literature reviews by Danielson and Hubbard, D’Angelo and 

others, Putman and others, and Knapp did not address this potential mitigation measure on either 

the local or landscape scale. (See references 58, 61, 176, and 231.) 
 99 

Some modeling efforts found a relationship between traffic volume and WVCs and suggest 

reduced traffic volumes as a potential solution to WVCs.(17,19,20) The modeling effort only 

identified a relationship between roads with a certain traffic volume and the presence of WVCs; 

it did not prove a causal relationship. Jaarsma and Willems for example, suggest implementing 

traffic calming on the more minor rural roads in order to shift the traffic onto a few major 

highways.(20) A similar number of studies found that higher volumes on roadways reduced the 

number of WVCs (see section in chapter 2 on traffic density and speed). As presented in a later 

section on “Undesired Effects,” lower densities may actually increase crash rates. 

Citing road mortality as one of the reasons, Friends of the Earth is campaigning for a 10-percent 

reduction in overall road traffic levels in the UK by 2010, as compared to 1990 levels.(232)

However, it is unclear how to feasibly achieve this reduction. 

Case Studies and Contacts 

Reducing traffic volume has not been attempted directly as a mitigation measure for reducing 

WVCs. However, Catharinus Jaarsma has done extensive modeling on possible impacts (see 

description in previous paragraphs): Catharinus Jaarsma, Land Use Planning Chair, Wageningen 

University, the Netherlands. 

Direct Benefits 

Some modeling studies suggest reduced traffic volumes will result in decreased WVCs, although 

other studies found the opposite result. The relationship between road mortality, traffic volume 

and animal density, and mobility warrants further study.(22) 

Indirect Benefits 

Numerous indirect benefits can be suggested such as reduced energy demand, reduced pollution, 

etc. However, one should keep in mind the more holistic picture. For example, traffic calming 

measures may shift traffic to more major highways, but this would actually require drivers to 

travel further to get where they are going, ultimately increasing fuel use and emissions. 

Undesirable Effects 

Lower traffic volumes do not necessarily equate with fewer roadkills.(20) As noted above, this 

method may actually increase the number of WVCs. Additionally, limiting traffic on a roadway 

may have adverse economic impacts. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 
 100 

TEMPORARY ROAD CLOSURES 

During periods of high animal movement, roads could be temporarily closed. Several temporary 

closures have been implemented for the reduction of WVCs. Some low-volume paved roads are 

closed seasonally during the night. In Delaware Water Gap National Recreation Area, the River 

Road is closed annually during the night (6 p.m. to 6 a.m.) in March and April when there is a 

forecast calling for rain with temperatures greater than 10 oC (50 oF). This allows multiple 

amphibian species to cross the road during their seasonal migration.(233,234) In the Shawnee 

National Forest, the LaRue Road at the base of the bluffs adjacent to LaRue Swamp is closed day 

and night from March 15 to May 15 and September 1 to October 30 to allow amphibians and 

reptiles, including several snake species, to conduct their seasonal migration.(235) In East 

Brunswick, NJ, the Beekman Road is closed several nights in the spring to allow spotted 

salamanders to cross the road during their seasonal migration.(236) 

Case Studies and Contacts 

For information on road closure in the LaRue-Pine Hills in the Shawnee National Forest, contact: 

Mississippi Bluffs Ranger District, 521 North Main Street, Jonesboro, IL 62952, (618) 833-8576. 

Direct Benefits 

Although the magnitude of impacts on WVCs has not been documented in the literature, it is 

clear that while a road is closed to traffic, there will be no WVCs. 

Indirect Benefits 

Like the previous section, numerous indirect benefits can be suggested such as reduced energy 

demand, reduced pollution, etc. (assuming that drivers do not just take an alternative route). 

Undesirable Effects 

Closing roads may have adverse economic impacts and accessibility issues. Road closures may 

require people to reroute, actually requiring drivers to travel further to their destination, 

ultimately increasing fuel use and emissions. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 

REDUCE VEHICLE SPEED 

For areas with high WVC frequency, reducing vehicle speed is occasionally suggested as a 

mitigation strategy. Before discussing the methods and implications of this strategy, it is 
 101 

important to understand the different types of speeds associated with the design and operation of 

a highway: 

• The design speed is “a selected speed used to determine the various geometric design 

features of the roadway.”(1) Certain minimum design standards are used for different 

design speeds. A higher design speed typically means higher minimums for curve radius, 

lane widths, shoulder widths, clear zone widths, and other design parameters. Higher 

design speeds also mean lower maximums for the number of access points (e.g., 

intersections, driveways, or interchanges) per mile. 

• After a road is built, a spot speed study is done. Operating speed is determined as “the 

speed at which drivers are observed operating their vehicles during free-flow conditions. 

The 85th percentile of the distribution of observed speeds is the most frequently used 

measure of the operating speed associated with a particular location or geometric 

feature.”(1) Speed studies are typically done before speed limit signs are installed, or 

speed limit signs are covered during the study. The theory assumes that drivers are the 

best judge of a safe driving speed of a roadway and 85 percent of the people will travel at 

reasonable speeds. 

• The enforceable posted speed limit is the maximum legal speed at which a vehicle is 

allowed to travel. These are typically set near the operating speed (85th percentile speed). 

• When a portion of the roadway has characteristics where the design speed is less than that 

of the rest of the road, an advisory speed can be posted. For example an advisory speed 

sign in the Netherlands is located at a gap in exclusionary wildlife fencing (figure 39). 

Advisory speeds are lower than the posted speed limit and are not enforceable other than 

by using basic “reasonable and prudent” laws. 
 102 

Figure 39. Photo. Advisory speed sign in The Netherlands located at a gap in exclusionary 

wildlife fencing (copyright: Marcel Huijser). 

Under typical circumstances, the design speed, operating speed, and posted speed should be 

almost equal for a given roadway. With this in mind, there are effectively three ways to reduce 

vehicle speed: (1) reduce the posted speed, (2) reduce the design speed through traffic calming or 

redesign, and (3) post an advisory speed. 

REDUCE VEHICLE SPEED BY REDUCING THE POSTED SPEED LIMIT 

This mitigation entails reducing the posted speed. The ability to do this depends on who owns 

the roadway (state, county, city), as well as the legislation and guidelines governing those 

agencies. Once approval for the reduced speed is obtained, this mitigation is implemented by 

replacing the existing speed limit signs. 

One location where posted vehicle speeds were reduced to mitigate WVCs is in Jasper National 

Park in Alberta, Canada, on the Yellowhead Highway. This roadway is a rural two-lane highway 

in a national park, with 3.7-m (12-ft) lane widths, and 3-m (10-ft) shoulders.(237) Passing sight 

distance exists for most of the length. Passing sight distance is defined as “determined on the 

basis of the length needed to complete normal passing maneuvers in which the passing driver can 

determine that there are no potentially conflicting vehicles ahead before beginning the 

maneuver.”(1) 

Prior to the mitigation, the speed limit for the roadway was 90 km/h (56 mi/h). Traffic in 1998 

was 1.2 million vehicles per year with a high percentage of trucks, buses, and recreational 

vehicles. The area includes grizzly bear, white-tailed deer, mule deer, bighorn sheep, and elk. 
 103 

In 1991, the speed limit was reduced from 90 km/h (56 mi/h) to 70 km/h (43 mi/h) on three 

sections of the road; 2.5, 4, and 9 km (1.5, 2.5, and 5.6 mi) in length. Bertwistle reported that on 

average, 5,475 speeding tickets are issued each year (although he was not specific as to if these 

were in the 70 km/h (43 mi/h) zones or on the highway as a whole). Even with the speed limits 

and enforcement, a speed study in 1995 at two of the speed reduction locations showed that less 

than 20 percent of the vehicles obeyed the 70 km/h (43 mi/h) speed limit. Bertwistle reported 

that bighorn sheep collisions actually increased in the reduced speed zones and decreased in the 

control areas (the 90 km/h (56 mi/h) areas). Elk collisions were monitored at one reduced speed 

location and both the control and the reduced speed zones had increases in elk vehicle collisions. 

Bertwistle stated that there was a relationship between reducing the posted speed and the 

frequency of elk-vehicle collisions; however, the data presented in the paper appear to be 

inconclusive. 

A report by Biota Research and Consulting, Inc. summarizes WVCs in the Jackson, WY area.(213)

On a particular 1.4-km (0.9-mile) stretch of highway, the authors suggest highway lighting as a 

solution, because even with the posted speed limit reduced to 56 km/h (35 mi/h), drivers 

continue to strike and kill deer. The report does not state whether or not there was a decrease in 

WVCs from the posted speed limit reduction. 

Often reduced speed zones are tied to other mitigation methods. A variable speed limit is 

associated with an animal detection system in Switzerland. (This system is described in the 

section on Animal Detection Systems earlier in this chapter.) Advisory speeds have also been 

used in conjunction with gaps in exclusionary fencing in The Netherlands, as previously 

mentioned (figure 39). 

Case Studies and Contacts 

For further information on the reduced speed limits in Jasper National Park, contact 

Jim Bertwistle, Warden, Jasper National Park, Alberta, Canada, (403) 852-6155. 

Guidelines 

If reduced speed zones are implemented, the following design considerations are recommended: 

• Consider additional signing in advance of the reduced speed zones to inform motorists of 

the intent and hazard present. In Jasper National Park the signs stated “Slow Down for 

Wildlife.” 

• Reduced speed zones will have limited effectiveness without consistent visible 

enforcement, especially if the posted speed is significantly below the operating speed or 

design speed. 

Direct Benefits 

The effect of reducing vehicle speed on WVCs is unclear. However, for all crashes, reducing 

vehicle speeds will generally reduce the frequency of severe crashes (i.e., human injury or 

fatality).(238) 
 104 

Indirect Benefits 

Indirect benefits cited in the literature include 

• Fines collected from regular enforcement. 

• Increased fuel economy: West and others showed that for a mix of vehicle types, fuel 

efficiency peaked at about 88 km/h (55 mi/h).(239)

• Reduced emissions: the exact relationship is unclear but they are closely related to fuel 

efficiency. 

• Reduced injury severity of crashes. 

Undesirable Effects 

Extreme caution should be taken in reducing the posted speed limit excessively below the 

operating speed. Such a reduction can set up a situation where motorists are encouraged to break 

the law and leads to speed dispersion (the spread of vehicle speeds). Instead of a tight 

distribution of speeds for vehicles on the road, there tends to be two speed groups: one group of 

vehicles will travel at the posted speed limit and another will travel at the operating speed. It has 

been shown that speed dispersion increases crash rates even if average speeds decrease. Solomon 

and Cerrelli found that vehicles traveling close to the average speed had the lowest crash 

involvement rates.(240,241) Crash involvement rate not only increased for faster vehicles, but also 

for slower vehicles. Garber and Gadiraju found a similar U-shaped relationship, where the 

further the posted speed was from the design speed, the higher the crash rate for the roadway.(242)

Speed dispersion is particularly an issue on two-lane rural roads (where WVCs occur most 

often), because it increases the number of vehicles passing in unsafe situations. 

Costs 

Costs include the following: 

• The initial cost of replacing speed limit signs. 

• The cost of regular enforcement. 

• Additional costs in increased travel time need to be considered. 

• Potential increase in head-on and other collisions due to speed dispersion. 

REDUCE VEHICLE SPEED BY TRAFFIC CALMING/REDUCING DESIGN SPEED 

Reducing the design speed of a road may be more effective in reducing vehicle speed than 

reducing the posted speed limit. A lower design speed typically relates to sharper horizontal and 

vertical curves, narrow lane widths, narrow or no shoulders, and narrow clear zones (i.e., 
 105 

obstructions such as trees closer to the roadway). In addition to the basic highway geometrics, 

there are numerous traffic calming methods used to slow vehicles down. These are typically used 

in residential neighborhoods or on a highway approaching a town, and rarely on major highways 

where most WVCs occur. Traffic calming treatments include speed bumps/humps, traffic circles, 

curb extensions, sidewalk extensions, raised medians, and rumble strips. 

Gunther and others showed that in Yellowstone National Park, roads with higher posted speed 

limits had higher WVC occurrences.(243) His primary evidence is shown in figure 40, where an 

88 km/h (55 mi/h) roadway has significantly higher roadkill per mile than roadways with lower 

posted speed limits. Notice, however, that WVC frequencies do not increase until 88 km/h 

(55 mi/h) speed limit. The 88 km/h (55 mi/h) road (U.S. 191) used by Gunther in this analysis is 

not an interior roadway and experiences much higher traffic over the year than the other roads 

considered. Gunther did show that internal roadways that were reconstructed with higher design 

speeds did see an increase in roadkill. 

0

5

10

15

20

15 25 35 40 45 55

Posted Speed (MPH)

Roadkill per Mile

1 mi/h = 1.61 km/h 

Figure 40. Graph. Roadkill by posted speed limit in Yellowstone.(243) 

Below are three examples of traffic calming applications for wildlife: 

One example is shown in figure 41 where speed bumps are used to reduce vehicle speed for 

Cassowaries (Casuarius casuarius), a large bird species in Queensland, Australia. The top sign 

originally displayed a warning for a speed bump, but was vandalized with a black marker to look 

like a dead bird. 
 106 

Figure 41. Photo. Speed bumps used to reduce WVCs in Australia (copyright: Marcel Huijser). 

(Please disregard graffiti on signs.) 

A second example is the installation of four “slow points” on a road in Tasmania that 

experienced a dramatic increase in collisions with eastern quolls (Dasyurus viverrinus) and 

Tasmanian devils (Sarcophilus laniarius) after the road section in a national park was widened 

and sealed and modal speed increased by 20 km/h (12.4 mi/h).(244) In addition, after the initial 

widening the population size of the two species declined substantially and the eastern quoll 

population became extinct. The slow points consisted of concrete barriers with a “Give Way” 

sign that constricted traffic to a single lane in the center of the road in or close to locations that 

had a concentration of roadkill.(244) The tight curves and the merging of traffic forced vehicles to 

slow down. After the installation of the slow points, the median vehicle speed in the center of the 

road section dropped by about 20 km/h (12.3 mi/h) (17–35 percent reduction), while vehicle 

speed at the outer two slow points close to the park boundary and wildlife zone boundary was 

only reduced by 1–7 percent. In addition, road mortality became more sporadic; the eastern quoll 

population became reestablished and was at 50 percent of its size before the road was widened 

and sealed two years after the installation of the slow points.(244) Furthermore, there was some 

indication that Tasmanian devil population was recovering as well. 
 107 

A third example is the installation of (1) rumble strip patches along a road in south Florida in 

combination with (2) a black-on-yellow warning sign that reads “PANTHER CROSSING NEXT 

X MI” that has (3) a permanently activated flashing amber light installed on top of the warning 

sign. These mitigation measures are designed to increase driver alertness and to reduce vehicle 

speed to reduce collisions with the Florida panther. 

Case Studies and Contacts 

Although this mitigation has not been implemented directly, Kerry Gunther has done extensive 

modeling on potential impacts of design speed reductions: Kerry Gunther, Bear Management 

Office, Yellowstone National Park, kerry_gunther@nps.gov. 

For more information on the slow points installed in Tasmania, contact Menna Jones, 

Department of Zoology, University of Tasmania, GPO Box 252-5, Hobart, Tas. 7001, Australia, 

E-mail: Menna.Jones@utas.edu.au. 

Direct Benefits 

Direct benefits of this measure in reducing WVCs are inconclusive. 

Indirect Benefits 

Lower speeds may reduce the number of fatal crashes and improve the overall safety of the 

roadway. 

Undesirable Effects 

Certain traffic calming measures have maintenance issues with snow removal. Also, the 

economic impacts of longer travel times should be considered. 

Costs 

No costs were identified in the literature review. 

Guidelines 

For further information on typical traffic calming measures and design guidelines, refer to the 

FHWA/ITE report on “Traffic Calming: State of the Practice” available at: 

http://www.ite.org/traffic/tcstate.htm (accessed January 25, 2007). 

REDUCE VEHICLE SPEED BY POSTING ADVISORY SPEED SIGNS 

Advisory speeds are typically only used in conjunction with other mitigation methods (primarily 

roadway warning signs). The results of those implementations are not revisited here, as they are 

discussed in other sections. 
 108 

WILDLIFE CROSSING GUARDS 

In some cases, individuals will direct traffic in areas where animals cross the roadway. This 

situation often occurs in national parks where mini-traffic jams (referred to as “animal jams”) 

occur as vehicles stop on the highway to view wildlife. In some cases, this traffic control is 

conducted by park staff. In other situations, it may be the work of volunteers. For example, a 

story in USA Today on September 24, 2006, by Mick Cochran told of the volunteer group calling 

itself the Bugle Corps in Rocky Mountain National Park that manages traffic along the park’s 

roads during the Rocky Mountain elk (Cervus elaphus nelsoni) rutting (breeding) season.(245)

Case Studies and Contacts 

Most local technical assistance program (LTAP) centers offer flagger training and certification. 

Contact information for LTAP centers is located at: http://www.ltapt2.org/ (accessed January 25, 

2007). 

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

When vehicles stop to view wildlife, it creates an unsafe situation with vehicles weaving around 

the stopped vehicles and pedestrians walking along roadways. This mitigation measure may 

reduce vehicle-vehicle and vehicle-pedestrian collisions. 

Undesirable Effects 

Staff or volunteers that manage traffic are exposed to potential injury from inattentive motorists. 

Costs 

Costs include training costs and the cost of the time spent by the individuals managing traffic. 

Costs of safety vests and stop/yield paddles (mandatory) are minimal. 

Guidelines 

Volunteers or staff should be trained in traffic control. 

Note that the application of this mitigation measure is typically in national parks or other 

protected areas where wildlife may be habituated to people, traffic, and roads. In addition, the 

measure is typically only deployed when traffic volume is relatively high and when staff or 

volunteers are available. 
 109 

CHAPTER 6. MITIGATION METHODS THAT SEEK TO INFLUENCE ANIMAL 

BEHAVIOR 

These WVC reduction strategies are designed to change where, how, and when wildlife cross 

roads by modifying the animals’ behavior without the use of major structures on or along the 

roadway. The specific mitigation measures reported on in this chapter are as follows: 

• Deer reflectors and mirrors. 

• Audio signals in right of way or attached to vehicles. 

• Olfactory repellents. 

• Deer flagging models. 

• Hazing. 

• Deicing alternatives. 

• Intercept feeding. 

• Influence species composition or minimize nutritional value of vegetation in the right of 

way. 

• Remove carcasses along transportation corridors. 

• Increase median width. 

DEER REFLECTORS AND MIRRORS 

Deer mirrors and reflectors are roadside installments intended to act as visual wildlife repellents. 

Mirrors directly reflect vehicle headlights off the roadway and into the surrounding right of 

way.(61) Reflectors beam colored reflected light from headlights into roadside habitat (Swareflex, 

D. Swarovski & Co., Wattens, Austria, http://www.swareflex.com/ (accessed January 26, 2007)) 

or onto the roadway itself (Strieter-Lite, Strieter Corp., Rock Island, IL, http://www.strieterlite.com/).(246) 

Most studies testing the effectiveness of mirrors and/or reflectors on reducing WVCs found that 

they had (1) no effect, (2) mixed results, or (3) inconclusive results. (See references 38, 59, 247, 

248, 249, 250, 251, and 252.) Differences in experimental design and in the variety of models 

tested confound the comparison of results.(231) However, Schafer and Penland did find a 

significant reduction (88 percent) in WVCs using Swareflex reflectors in Washington State.(211)

Pafko and Kovach found in Minnesota that reflectors reduced rural incidences by 50–97 percent, 

but suburban metropolitan WVC incidences increased.(250) 
 110 

The Strieter-Lite company suggests there is scientific proof that their reflectors do work 

(78–90 percent reduction in DVCs) and that reflective luminance (brightness) is not a major 

factor, because wild animals have acute night vision.(253,254) Sivic and Sielecki conducted a 

spectrometric evaluation of Swareflex and Strieter-Lite wildlife warning reflectors and noted 

operational implications of low light reflection intensities.(255) Reflectors require suitable 

placement, alignment maintenance, and regular cleaning; however, in a roadside application it is 

impossible to keep reflectors clean at all times.(72,254,256) Possible reasons why reflectors and 

mirrors do not result in fewer roadkill include improper installation, lack of maintenance (no 

replacement of missing reflectors or realigning them after they became out of alignment), and 

dirty mirrors/reflectors (especially in winter). 

Utah DOT discontinued use of reflectors due to an increase in deer kills and difficulty in keeping 

reflectors clean; high installation and maintenance/cleaning costs were also factors.(256) Thirtynine percent of Swareflex reflectors used in Wyoming showed deterioration after 3 years.(248) In 

British Columbia, reflectors were prone to theft and vandalism.(72) Where mirrors and reflectors 

work in reducing WVCs, it may be a result of driver behavior, particular site characteristics, or 

rural versus suburban landscapes.(250,251,257) 

Mirrors and reflectors are addressed in several literature reviews and annotated bibliographies. 

(See references 58, 61, 176, 231, 248, 258, and 259.) Knapp and others summarized 10 studies, 

five of which concluded that roadside reflectors did not appear to impact DVCs, two of which 

concluded that they did, and three reached inconclusive or mixed results.(53) 

Studies testing the influence of reflectors on animal behavior found little or no evidence of 

avoidance.(59,246,257) A study of Strieter-Lite wildlife warning reflectors in four colors (red, white, 

blue-green, and amber) found them to be ineffective at altering white-tailed deer behavior so that 

DVCs might be prevented.(246) Interestingly, data indicated that deer increased negative 

behavioral responses toward vehicles in the presence of reflectors.(246) Ramp and Croft, however, 

found Swareflex reflectors produced a weak fleeing response in kangaroos.(260) Ujvari and others 

found that deer initially responded to reflectors with alarm and flight but then became habituated 

to the light reflection.(261) D’Angelo and others recommend that future development of deerdeterrent devices for WVC mitigation be based on empirical knowledge of deer senses and 

behavior.(246) 

Case Studies and Contacts 

For information on a couple of the reflectors that are available, contact Swareflex Reflectors, 

D. Swarovski & Co., Wattens, Austria, www.swareflex.com, and Strieter-Lite, Strieter Corp., 

Rock Island, IL, http://www.strieter-lite.com/ (accessed January 26, 2007). 

For information on effectiveness of reflectors on animal behavior, contact Gino D’Angelo, 

Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 

30602, (706) 227-6867, gid4895@owl.forestry.uga.edu. 
 111 

Direct Benefits 

Roadside reflectors and mirrors are categorized as “tried” (as defined by AASHTO Safety 

Strategy Groups) and “used with conflicting safety analysis results” in a critical evaluation of 

DVC crash countermeasures.(176) 

Indirect Benefits 

This mitigation approach allows for animal movements at grade and allows animals to change 

where they cross over time. 

Undesirable Effects 

Deer have been documented to move toward vehicles in the presence of reflectors.(246) 

Costs 

A manufacturer advertises total cost of installation with reflectors, posts, equipment, and labor to 

be $4,000–6,000 per km ($7,000–10,000 per mi). The average life of reflectors is 12.5 years, so 

costs amount to $169–199 per km ($272–320 per mi) per year. Maintenance cost per mile per 

year is $500 ($300 per km per year) (Strieter-Lite, Strieter Corp., Rock Island, 

IL, http://www.strieter-lite.com/).(262) In British Columbia, reflectors cost approximately $10,000 

per km ($16,000 per mi) to install along both sides of a highway, and maintenance costs range in 

the order of $500–1,000 per km ($800–1,600 per mi) annually.(72) 

Guidelines 

The manufacturers have installation guidelines. Regular maintenance, e.g., cleaning of the 

reflectors, may be needed. 

AUDIO SIGNALS IN RIGHT OF WAY OR ATTACHED TO VEHICLE (DEER 

WHISTLES) 

Audio animal warning devices are intended to alert wildlife of oncoming traffic. Sav-A-Life 

Deer Alert (Sav-A-Life Industries, New York, New York, http://www.sav-a-life.com/ (accessed 

January 26, 2007)) and Game Tracker’s Game Saver, marketed as vehicle-mounted ultrasonic 

animal warning devices, elicited no response in 150 groups of free-roaming mule deer in 

with/without trials.(263) Behavioral observations of captive kangaroos in response to the Shu Roo, 

a vehicle-mounted ultrasonic kangaroo deterrent, did not differ in the on or off position.(264) 

Many literature reviews and annotated bibliographies deem audio repellants ineffective in terms 

of modifying animal behavior for the goal of WVC reduction.(See references 58, 61, 74, 176, 

216, 231, 265, and 266.) 

A roadside wildlife warning system utilizing high-frequency sounds has been developed 

(International Road Dynamics, Inc., (IRD) Saskatoon, Saskatchewan, 

Canada, http://www.irdinc.com/ (accessed January 26, 2007)).(267) Results from a study were not 

conclusive, and the system is no longer in service (Rob Bushman, IRD Inc., personal 
 112 

communication). While it is recognized that the results may not apply to highways, a wildlife 

warning system was installed along a railroad in Poland.(268) The system is activated when trains 

approach.(268) The effectiveness of this system has not been evaluated. 

Another roadside wildlife warning system was developed by Firma Günter Josef Folda in 

Austria.(269) Headlights from approaching cars activate equipment that is integrated with the 

poles and reflectors that delineate the roadway (Edward Mulka, JAFA Technologies, Inc., 

personal communication). Once activated, the equipment emits a high-pitched alarm sound along 

with a supplemental blue light strobe light (Edward Mulka, JAFA Technologies, Inc., personal 

communication).(269,270) Unconfirmed data from Austria (between the cities of Nassereith and 

Imst in the Gurgltal on the Miemingerstraße road) indicate that the equipment may reduce WVCs 

by 85–93 percent.(270) The equipment is encased in a weather-resistant box and is powered by 

solar cells, batteries, or both (Edward Mulka, JAFA Technologies, Inc., personal 

communication).(270) The equipment weighs less than a pound and can be mounted on trees or 

small poles. The equipment can be directed such that the sound and strobe emitter face away 

from the road in the direction of wildlife that may be in the process of approaching the road 

(Edward Mulka, JAFA Technologies, Inc., personal communication).(270) 

A study of fallow deer (Dama dama) behavioral responses to acoustic road markings showed 

that while behavioral responses differed initially, deer became completely indifferent to the 

acoustic stimuli within 10 days.(271) 

In a comparison of whistle acoustic frequencies and intensities and deer hearing abilities, 

Scheifele and others determined closed-end whistles produced frequencies of ~3.3 kHz with little 

variation with changes in air pressure, while open-end whistles emitted frequencies of ~12 kHz 

with significant variation depending on air pressure.(272) Deer hearing sensitivity is estimated to 

be between 2 kHz and 6 kHz.(272,273) Taking into consideration the masking effect of road and car 

noise, however, deer are not likely to be able to hear the whistles.(263,272) Recordings made during 

dynamic drives found that the Shu Roo signal was not detectable above the noise of four vehicles 

traveling at different speeds, yielding no difference whether the device was turned on or off.(264)

Further, if whistles were audible in combination with vehicle and road noise, there is no evidence 

that they affect animal behavior and habituation to these sounds is possible. (See references 263, 

264, 271, 272, and 274.) 

Case Studies and Contacts 

Contacts for some audio signal manufacturers are: 

• Sav-A-Life Industries, New York, NY, http://www.sav-a-life.com. 

• Rob Bushman, International Road Dynamics, Inc., http://www.irdinc.com/search. 

• WIWASOL-II. Firma Günter Josef Folda, Perkonigweg 3, 9311 Kraig, Austria, 

Phone: +43 (0) 664 2301980, Fax: +43 (0) 720 555870, 

Email: office@wildwarner.at http://www.wildwarner.at/pages/31alhomepag.html. 

Distributor USA: Edward A. Mulka, JAFA Technologies, Inc., 213 Hooton Road, Mt. 

Laurel, NJ 08054, Tel/Fax: (856) 802-9095, Cell: (856) 278-1597, Email: emulka@jafatech.com, http://www.jafatech.com/. 
 113 

Direct Benefits 

Deer whistles are categorized as “tried” (as defined by AASHTO Safety Strategy Groups) and 

“used with conflicting safety analysis results” in a critical evaluation of DVC crash 

countermeasures .(176) 

The effectiveness of the IRD system is inconclusive. Maintenance staff anecdotally felt the 

system was effective, but the data were inconclusive, possibly since not enough data were 

collected. Currently the IRD system is not in use.(Rob Bushman, IRD Inc., personal 

communication).

The effectiveness of the WIWASOL-II system may be 85–93 percent, but these results are 

currently unconfirmed.(270) 

Indirect Benefits 

This approach accommodates unrestricted animal movements at grade. 

Undesirable Effects 

Audio signals may frighten animals away in areas where there may be interest in establishing or 

improving habitat connectivity across a highway. 

Costs 

The Sav-A-Life Deer Alert individual vehicle-mounted devices cost $23.50 each. 

For a test installation of a roadside-based audio signal system along a 6-km (3.7-mi)-long road 

section, the costs were about €19.000.(270) 

Guidelines 

If auditory warnings are used, their frequency must be within the auditory range of the species, 

and they must not be drowned out by the surrounding road and vehicle noise. 

OLFACTORY REPELLENTS 

Olfactory repellents involve odorous chemical or organic compound applications along roadways 

to act as deterrents for wildlife. 

A literature review of capsaicinoids, synthesized animal odors, other animal products, garlic, 

particulates, soaps, thiram, bittering agents, natural predator excretions, and putrescent egg 

determined the latter two hold the most potential for keeping ungulates away from roadways but 

have not been field tested.(176,275) An experimental study and literature review found olfactory 

repellents did not prove effective as area repellents for large-scale application on travel corridors, 

making them unsuitable for use in reducing WVCs.(276) Other literature reviews that addressed 

effectiveness in terms of reducing WVCs have determined that olfactory repellents have not been 

adequately tested, show only limited effectiveness, or are impractical because of the need to 
 114 

repeat applications, especially after precipitation events. (See references 22, 58, 61, 176, 216, 

277, and 278.) Future development of olfactory repellent measures requires further study of 

wildlife behavioral responses on a range of species and of the potential for animal 

habituation.(176,260,279) 

Experimental scent marking using Duftzaun (HAGOPUR GmbH, Landsberg am Lech, 

Germany), a mixture of bear, gray wolf, Eurasian lynx (Lynx lynx), and human components, 

showed an 85 percent reduction in moose-train collisions in Norway, but results were 

questionable given that short treatment distances (500 m (1,640 ft)) yielded small and variable 

samples sizes for the number of collisions.(227) 

Captive trials of Wolfin® (Pro Cell Biotenik, Hornefors, Sweden), a synthetic scent repellent, 

showed no repellency of caribou or black-tailed deer.(280,281) The repellent Plant Plus (Roe Koh 

and Associates Pty. Ltd., Mornington, Victoria, New Zealand), a synthetic canine predator odor, 

had aversive effects on one species of marsupial but attracted another, indicating a need for more 

research.(260) Captive trials of Deer Away® Big Game Repellent (Intagra, Inc. Lakeville, 

Minnesota), a putrescent whole egg repellent, initially altered caribou feeding behavior, but 

feeding times and amount eaten returned to pretreatment levels.(280) 

Manufacturers of a proprietary “chemical fence” (repellent chemicals encapsulated in slow 

release organic foam and applied to roadside posts or trees) reported some repellency and a 

reduction in frequency of roe deer-vehicle collisions in one treated section.(9,282) However, a 

more detailed assessment found DVCs rose in untreated sections.(58,283) A roadside wildlife 

warning system utilizing scent repellents has been developed (International Road Dynamics, 

(IRD) Inc., Saskatoon, Saskatchewan, Canada, http://www.irdinc.com/), but results from a study 

were not conclusive and the system is no longer in service (Rob Bushman, IRD Inc., personal 

communication).(267)

Case Studies and Contacts 

For information about effectiveness of repellents on animal behavior, contact Lisa Shipley, 

Department of Natural Resource Sciences, Washington State University, (509) 543-8955 or 

Marion Carey, Project Monitor, Environmental Affairs Office, Washington Department of 

Transportation, (360) 705-7404. 

Direct Benefits 

In terms of reducing WVCs, evidence for effectiveness remains sparse and temporary at best.(22)

Repellents are categorized as “experimental” (as defined by AASHTO Safety Strategy Groups) 

and “not generally used and rarely studied for safety impacts” in a critical evaluation of DVC 

crash countermeasures.(176)

Indirect Benefits 

No indirect benefits were identified in the literature review. 
 115 

Undesirable Effects 

Kinley and Newhouse caution that unintended negative effects may arise from olfactory repellent 

application and recommend a cost-benefit analysis of associated safety, economic, and 

ecological factors.(275) Potential negative effects may include attracting predators to the roadside 

and causing a panic reaction (instead of avoidance) in ungulates resulting in erratic movements 

toward the roadway. 

Costs 

Costs should take into consideration maintenance requirements, time intervals for reapplications, 

the area to be treated, and ecological impacts.(22,176) 

According to the literature, one liter of Plant Plus concentrate costs $30 (currency was not 

specified, but presumably Australian dollars).(284)

Guidelines 

If olfactory repellents are used, it is important to ensure that the repellant works to deter animal 

movement and that animals do not become habituated to them. 

DEER FLAGGING MODELS 

Deer flagging models are based on the behavioral characteristic of white-tailed deer that raise 

their tails to expose the white underside when fleeing. Tail flagging, however, has not been 

shown to act as a warning signal to other members of the species.(285)

A single deer flagging model study was found.(286) The researchers used painted wooden 

silhouette models of deer with painted or actual deer tails in a control/treatment experiment and 

found the models to be ineffective for deterring deer from the roadway.(286) A number of 

confounding factors make it difficult to determine whether or not this mitigation alternative is 

viable.(176) Future studies that consider pertinent variables (e.g., fluctuations in deer movements) 

could validate or refute this study and address potential safety or DVC impacts of deer flagging 

models.(176) 

Case Studies and Contacts 

For review information about deer flagging models, contact Keith Knapp, Texas Transportation 

Institute, Work Zone and DMS Program, Room 410D, 3135 TAMU, College Station, TX 

77843-3135, (979) 845-5686, k-knapp@tamu.edu. 

For further information about deer tail flagging, contact Tim Caro, University of CaliforniaDavis, Wildlife, Fish, and Conservation Biology Department, 1395 Academic Surge Building, 

95616, (530) 752-0596, tmcaro@ucdavis.edu. 
 116 

Direct Benefits 

Deer flagging models are categorized as “experimental” (as defined by AASHTO Safety 

Strategy Groups) and “not generally used and rarely studied for safety impacts” in a critical 

evaluation of DVC crash countermeasures.(176) 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 

HAZING 

Hazing or aversive conditioning is the practice of dispersing wildlife by frightening them, which 

has been done using such things as lights, lasers, water sprays, pyrotechnics, cannons, guns, 

helicopters and predatory-resembling chases. (See references 287, 288, 289, and 290.) 

Romin and Bissonette found 3 of 43 natural resource agency respondents used hazing as a 

method to reduce deer road mortality, one of which reported success.(3) Hazing was not effective 

in moose-vehicle collision mitigation efforts in Alaska.(78) In British Columbia, Roosevelt elk 

(Cervus canadensis roosevelti) were relocated when hazing failed as a WVC mitigation 

measure.(72) 

Green and blue lasers were found to be ineffective as frightening devices to disperse deer at 

night.(290) During treatment and control (observation with no laser) behavioral experiments, deer 

saw and followed the laser light and appeared to be more curious than frightened.(290) Red lasers 

were not tested because deer cannot see in the red portion of the spectrum.(290) Lasers have been 

proven to be effective on birds but not on deer, probably a result of species-specific threat 

perception (i.e., animals may not associate the disturbance with danger).(287,290) Lights and water 

sprays have only limited effectiveness.(287) 

Hazing with sounds (e.g., pyrotechnics, cannons, guns, and helicopters) may offer a temporary 

solution for dispersing animals, but noise is a consideration in areas of human populations.(287,288)

In a study of Key deer capture techniques, hazing with helicopters or shooting out of vehicles in 

residential areas was not attempted.(288) 
 117 

Aversive conditioning treatments resembling predatory chases by humans and dogs were 

effective in increasing flight responses in 24 moderately habituated radio-collared elk; habituated 

animals have been associated with WVCs in Banff National Park.(289) Natural wolf activity, 

however, appeared to reduce the efficacy of the aversive conditioning techniques (i.e., elk 

remained closer to town sites).(289) Aversive conditioning has shown some success in keeping 

grizzly bears off roadsides.(291) 

No scientific studies have been done to test the effectiveness of hazing on reducing WVCs, and 

hazing is not covered in other pertinent reviews on WVC mitigation measures.(61,176,231) DeNicola 

and others address hazing in managing deer in suburban environments but not within the context 

of WVC reduction.(287) Hazing can be difficult to implement in established conflict situations, 

because animal behavioral habits are difficult to change and habituation is possible.(287) 

Case Studies and Contacts 

For information about aversive conditioning in Banff National Park, contact Elsabe Louise 

Kloppers, University of Alberta, Canada, elsabekloppers@yahoo.ca. 

Direct Benefits 

Direct benefits are unknown. No scientific studies have been done to test the effectiveness of 

hazing on reducing WVCs.(61) 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

Aversive conditioning using humans was 15 percent less expensive than conditioning with dogs 

(Can$4,300).(289) 

Guidelines 

No guidelines were identified in the literature review. 

DEICING ALTERNATIVES 

The principal deicers used by highway agencies are chloride-based salts such as sodium chloride 

(NaCl), calcium chloride (CaCl2), and magnesium chloride (MgCl2), and acetate-based deicers 

such as potassium acetate, sodium acetate, and calcium magnesium acetate (Xianming Shi and 

Laura Fay, Western Transportation Institute, Montana State University, personal 

communication). 
 118 

The use of chloride salts in winter maintenance can attract wildlife to the right of way and may 

increase WVCs, especially in areas without natural salt licks.(See references 61, 74, 176, and 

292.) A study of 11 radio-collared moose in New Hampshire determined that all of their home 

ranges converged on the area containing roadside salt (NaCl) licks formed by runoff of road 

salt.(293) Implications associated with these roadside salt licks include increased moose-vehicle 

collisions and increased brain worm infections in moose and white-tailed deer.(293) Reducing the 

amount of salt or using alternative deicers (without salt), especially in areas of high WVCs, may 

reduce the attractiveness of the right of way.(294) 

Lithium chloride, a gastrointestinal toxicant, was found to effectively discourage captive caribou 

from eating treated food and may prove useful in reducing WVCs by discouraging ungulates 

from licking road salt.(280) CaMg-acetate has been recommended as an alternative to deice roads 

in Finland instead of NaCl.(74) Attempts at discouraging animals from road salt using the deicer 

calcium chloride were unsuccessful in Jasper National Park, Canada.(295) 

A study of the pattern of moose-vehicle collisions in relation to the presence of roadside 

saltwater pools showed that 43 percent of moose-vehicle collisions occurred within 100 m 

(328 ft) of a saltwater pool, higher than what would randomly be expected.(296) About the same 

number of collisions happened more than 300 m (984 ft) from a roadside saltwater pool.(176)

Knapp questions the assumption of the study (i.e., all locations have an equal chance for a 

collision).(176) 

Road salt and deicing alternatives are addressed in literature reviews; however, whether the 

reduction or replacement of the road salt would reduce WVCs involving ungulates remains 

unknown.(61,176,292)

Case Studies and Contacts 

For further information on efforts using deicing alternatives, contact Jim Bertwistle, Warden, 

Jasper National Park, Alberta, Canada, (403) 852-6155. 

Direct Benefits 

Whether the reduction or elimination of the road salt would reduce WVCs remains unknown.(176)

Deicing salt alternatives are categorized as “experimental” (as defined by AASHTO Safety 

Strategy Groups) and “used but not studied for safety impacts” in a critical evaluation of DVC 

crash countermeasures.(176) 

Indirect Benefits 

The intake of road salt has been found to be toxic to several bird species, porcupines, rabbits, 

deer, and moose that ingest it.(292,297) Reduction or elimination of road salt may reduce or 

eliminate this toxicity. 

Brain worm in moose and white-tailed deer is associated with road salt; elimination of road salt 

may reduce this occurrence.(293)
 119 

Undesirable Effects 

While the reduction or elimination of road salt may benefit certain species, alternatives to 

chloride salts may also be toxic to wildlife (Xianming Shi, Western Transportation Institute, 

Montana State University, personal communication), but this has not yet been specifically 

studied. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 

INTERCEPT FEEDING 

Intercept feeding provides strategically placed supplemental food sources in an attempt to divert 

animals away from roadways.(176) 

A two-year control/treatment experiment tested the effectiveness of intercept feeding as a means 

to reduce DVCs by diverting mule deer from roadsides in Utah.(298) The researchers concluded 

that intercept feeding may have reduced DVCs by as much as 50 percent.(298) However, no 

information was provided on the number of DVCs before intercept feeding stations were 

operational.(176)

After testing the effectiveness of scent marking, forest clearing, and supplemental feeding, 

researchers in Norway determined such mitigations might help reduce (but not eliminate) moosetrain collisions if applied over long distances.(227) Attempts at discouraging animals from road 

salt using intercept mineral baiting were unsuccessful in Jasper National Park, Canada.(295)

Intercept feeding may work in some cases, such as for short-term reductions in areas of high deer 

concentrations or in combination with other mitigation measures. (See references 61, 176, 216, 

and 298.) Intercept feeding is labor intensive and may create a dependency on supplemental food 

and actually increase population size.(216,298) Intercept feeding is addressed in several pertinent 

literature reviews. (See references 61, 176, 216, and 231.) 

Case Studies and Contacts 

For further information on intercept feeding efforts, contact Jim Bertwistle, Warden, Jasper 

National Park, Alberta, Canada, (403) 852-6155. 

Direct Benefits 

Intercept feeding is categorized as “experimental” (as defined by AASHTO Safety Strategy 

Groups) and “not generally used and rarely studied for safety impacts” in a critical evaluation of 

DVC crash countermeasures.(176) Additional study that can refute or validate the effectiveness of 

intercept feeding in reducing DVCs would be appropriate.(176)
 120 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

Intercept feeding may create a dependency on supplemental food or increase population size.(298)

Costs 

Intercept feeding is labor intensive.(216,298)

Guidelines 

No guidelines were identified in the literature review. 

INFLUENCE SPECIES COMPOSITION OR MINIMIZE NUTRITIONAL VALUE OF 

VEGETATION IN RIGHT OF WAY 

Roadside vegetation can attract wildlife to roads and increase their vulnerability to WVCs.(299,300)

The practice of planting trees near roadways for landscaping reasons can attract ungulates to the 

right of way and increase the risk of WVCs.(9) Several sources recommend managing vegetation 

in the right of way so that it does not serve as an attractant to wildlife (i.e., by planting 

unpalatable species, reducing forage quality, or applying noxious chemicals), while others focus 

on improving roadside habitat for wildlife. (See references 9, 74, 301, 302, 303, 304, 305, and 

306.) Techniques employing forage repellents, unpalatable species, and roadside brush removal 

have been used with limited effectiveness or are not cost efficient when broadly applied.(304)

An experimental study of vegetation removal along a railway line (20–30 m (66–98 ft) on each 

side) in Norway caused a 56 percent (+/- 16 percent) reduction in moose-train collisions.(228) The 

researchers concluded that there would be an economic benefit to perform vegetation removal 

treatments in areas with more than 0.3 collisions per km (0.48 per mi) but that local evaluations 

are necessary to confirm that vegetation cover is the main contributor to collisions in specific 

sections.(228) It is possible, however, that the experimental design may have overstated the 

collision reduction potential of vegetation removal.(176,228) 

A detailed literature review on roadside vegetation management, plant response to tissue 

removal, and ungulate foraging behavior yielded recommendations for more carefully designed 

cutting regimes as a countermeasure for reducing moose-vehicle collisions.(304) Willows cut in 

mid-July were found to be high in digestible energy and protein compared to plants cut at other 

times of the year and uncut controls, suggesting that summer brush cutting regimes may 

inadvertently be attracting moose with nutritious regrowth.(304,307) Cutting in early June results in 

browse with significantly less nutritional value for the first two years after cutting compared to 

plants cut later in the growing season and uncut controls.(304,307) Rea recommends cutting 

roadside brush in early spring soon after leaves develop to keep nutritional value and palatability 

to a minimum but recognizes operational challenges and limitations (i.e., ground too wet for 

tractor use, different ungulate species-specific responses to same management regime, etc.) and 

cautions that this countermeasure may not be suitable for all management areas.(304)
 121 

No studies were found that specifically analyze the WVC safety impacts of roadside 

management policies or plantings; however, a 1999 report by the Arizona Department of 

Transportation (ADOT) describes a future five-year monitoring plan to address the effectiveness 

of a number of mitigation measures (including those related to vegetation/habitat changes) on 

reducing WVCs.(176,308) The need to properly study the safety impact of vegetation management 

along roadways remains.(176)

Note: see also the section titled “Increase Visibility of Animals to Drivers: Vegetation Removal” 

in chapter 5. 

Case Studies and Contacts 

For information about roadside vegetation management, contact Roy Rea, Natural Resources and 

Environmental Studies, University of Northern British Columbia, Canada, reav@unbc.ca. 

Direct Benefits 

Roadside vegetation management is categorized as “tried” (as defined by AASHTO Safety 

Strategy Groups) and “used but rarely studied for safety impacts” in a critical evaluation of DVC 

crash countermeasures.(176)

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

Minimizing the nutritional vegetation may restrict the use of native vegetation along the 

roadside. In addition, reducing habitat quality may increase the road effect zone.(83)

Costs 

No costs were identified in the literature review. 

Guidelines 

Some guidance for implementing this mitigation measure is presented by Rea.(304)

REMOVE CARCASSES ALONG TRANSPORTATION CORRIDOR 

Highway safety is an impetus for timely removal of road-killed animals, and carcass composting 

may yield economic, ecological, and aesthetic benefits.(176,309) The carcasses of road-killed 

animals that are not removed may serve as food sources for other wildlife, attracting them to 

roads and increasing their vulnerability to WVCs.(176) Evaluation of the impact of roadside 

carcass removal on reducing WVCs has not been studied and has rarely been considered.(176)

While carcasses may be an attraction for scavengers, ungulates are not likely to be attracted or 

deterred by the presence of carcasses in the right of way. Therefore, carcass removal may not 

have a substantial effect on the number of DVCs and the total number of WVCs. Nonetheless, 
 122 

omnivores and carnivores, including some rare, threatened, or endangered species, may 

experience less road mortality as a result of the removal of food sources along the roadway. 

Case Studies and Contacts 

For information about carcass removal efforts in New York State, contact Elisabeth Kolb, 

Maintenance Environmental Coordinator, New York State Department of Transportation, 

(845) 575-6158. 

Direct Benefits 

Carcass removal, as an element in “roadway maintenance, design and planning policies,” is 

categorized as “tried” (as defined by AASHTO Safety Strategy Groups) and “used but rarely 

studied for safety impacts” in a critical evaluation of DVC crash countermeasures.(176)

Indirect Benefits 

Carcass removal may reduce the frequency of secondary roadkill of scavengers that feed on 

carcasses. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

In Canada, the clean-up and carcass removal and disposal costs for animal carcasses were 

estimated at Can$100 (deer), Can$350 (elk) and Can$350 (moose).(72) In Pennsylvania, the 

average cost for deer carcass removal and disposal in a certified facility was $30.50 per deer for 

contractors and $52.46 per deer for the Pennsylvania Department of Transportation in 

2003–2004 (Jon Fleming, Pennsylvania Department of Transportation, personal 

communication). 

Guidelines 

Carcass removal allows for easy data collection of roadkill, which helps with planning and 

monitoring mitigations for WVCs. A composting plant would mitigate the waste management 

issue. 

INCREASE MEDIAN WIDTH 

Crossing several lanes of traffic moving in opposite directions is a difficult task for an animal to 

perform. Wider medians can provide a “refuge” for the animals, giving them a break in their 

roadway crossing. Medians allow animals to deal with only one direction of traffic at a time, 

enabling them to stop partway across the roadway and identify and wait for an adequate gap in 

traffic before crossing the second half of the roadway. A literature review by Clevenger and 

Kociolek found that it was unclear whether or not a vegetated median increased the ability of 

wildlife to cross the road safely.(310)
 123 

Case Studies and Contacts 

No case studies were identified in this literature review. 

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

A wider median may provide a more aesthetically pleasing view to the driver. It may also allow 

for high beams to be kept on for longer periods at night to aid visibility. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 
 
 125 

CHAPTER 7. MITIGATION METHODS THAT SEEK TO REDUCE WILDLIFE 

POPULATION SIZE 

A comprehensive review by Knapp, Putman and others suggests that a reduction of the 

population size across a relatively wide area can be effective in reducing DVCs. (See references 

52, 53, 54, 58, 61, 62, and 311.) Nonetheless, actual data on the effectiveness of population 

reduction programs on WVCs are few. For example, a field test showed that a deer population 

reduction program in Minnesota reduced winter deer densities by 46 percent and DVCs by 

30 percent.(52)

Deer population sizes, especially those of white-tailed deer, have grown substantially over the 

last century in the United States.(55) This population growth is especially apparent since the 

1960s.(55,57) This increase in population size was triggered by better protection, a matrix of 

habitat providing cover (forests) and food (agriculture, silviculture), the loss or decline of their 

natural predators, and more recently, reduced hunting pressure by humans through an increase in 

refugia (private land, (sub) urban areas), and a decrease in hunters. (See references 55, 57, 312, 

313, 314, and 315.) Currently, white-tailed deer numbers are believed to be higher than they 

have ever been in the past several hundred years, causing or contributing to a series of problems, 

including DVCs. (See references 55, 57, 314, and 316.) This situation has triggered efforts to 

eliminate, reduce, or control the size of the deer population, especially white-tailed deer. 

The fertility of white-tailed deer depends on their population density; their reproduction is higher 

at relatively low densities than at higher densities. The fertility of white-tailed deer is weakly 

density dependent for adult does.(317) However, the fertility of first-year and yearling females is 

strongly density dependent, with very low fertility when population densities exceed 

30 deer/km2.

(317) These observations suggest that as population density is reduced, increased 

effort is needed to keep the deer density at the lower level. This phenomenon needs to be 

addressed in potential population size reduction programs. 

The relationship between deer population density and the number of DVCs seems intuitive but is 

often complex and variable.(59,60) Nonetheless, a comprehensive review by Knapp, Putman and 

others suggests that a reduction of the population size across a relatively wide area can be 

effective in reducing DVCs. (See references 52, 53, 54, 58, 61, 62, and 311.) 

This chapter discusses the following measures to reduce wildlife population size along roads 

• Wildlife culling. 

• Wildlife relocation. 

• Anti-fertility treatment. 

• Habitat alteration away from the road. 
 126 

WILDLIFE CULLING 

Wildlife culling involves a substantial reduction of the population size through eliminating a 

large number of individual animals over a short period of time. This measure is typically applied 

to or proposed for deer. The culling is sometimes done by recreational hunters through increased 

quota; sometimes it is done by professionals, especially if there are refugia for the deer (private 

land, (sub)urban areas). (See references 52, 312, 318, and 319.) 

A field test showed that a deer population reduction program in Minnesota reduced winter deer 

densities by 46 percent and DVCs by 30 percent.(52) Sharpshooting by professionals over bait 

was deemed to be the most effective and adaptable culling method in an urban setting, as 

opposed to controlled hunts in large parks and refuges or opportunistic sharpshooting by 

professionals.(52) 

The killing of does (females) is more effective for reducing the population size than the killing of 

bucks (males), not only because the reproductive potential of the herd is more effectively 

reduced, but also because does tend to stay in their existing home range while bucks have a 

greater tendency to disperse.(55) The does are less likely to migrate and establish new populations 

elsewhere. 

A modeling project by Porter and others showed that if female dispersal (i.e., animals that leave 

the area) was 8 percent, culling would have to reduce annual survival to 58 percent to maintain a 

population just under ecological carrying capacity (the maximum sustainable population 

size).(320) A further reduction of the annual survival to 42 percent would keep the population at 

0.5 of the carrying capacity.(320) 

Culling efforts are more likely to result in a substantial reduction in deer population size if the 

herd size is relatively small to begin with and if it is a closed population that does not allow 

influx of animals from nearby places. The effort has to be repeated periodically as the deer 

population will grow back to the same levels if the habitat conditions remain similar (i.e., it is not 

a one-time-only measure). In addition, the effort involved for population size reduction programs 

increases disproportionately with higher population size reduction goals, and substantial 

reductions (for example ≥50 percent) may be hard to obtain, perhaps capping the potential 

reduction in DVCs at 50 percent. Finally, wildlife culling can meet with strong public 

opposition. 

Case Studies and Contacts 

For information about a field test of four population management methods to reduce a deer 

population in Bloomington, MN, contact Michelle Doerr, 2887 Ulm Avenue, Stewart, MN 

55385, ewiggers@islc.net. 

For more information about a field test of the effects of baiting and supplemental antlerless 

seasons on deer harvest, contact Timothy Van Deelen, Department of Wildlife Ecology, 

University of Wisconsin, Madison, WI 53706-1598, trvandeelen@wisc.edu. 
 127 

Direct Benefits 

The relationship between deer population size and DVCs can be highly variable (see earlier 

discussion). Nonetheless, based on Doerr, Knapp and others, a certain percentage in population 

size reduction may result in a similar percentage in DVC reduction.(52,53) However, reductions in 

population size of 50 percent or more may be hard to obtain, perhaps capping the potential 

reduction in DVCs at 50 percent or less.(52)

Indirect Benefits 

Indirect benefits of reducing wildlife population size include reduced negative impacts from 

“overpopulation” on agricultural crops, silviculture, and natural vegetation.(55) 

Undesirable Effects 

Wildlife culling may not be favored or accepted by the public, especially in areas that have a 

high degree of ecological integrity (“hands-off” approach).(57,321,322) A public relations campaign 

should be considered along with a culling effort. 

Culling may not be possible or effective on private lands, in remote locations, or in urban and 

suburban areas.(55,312) If refugia are present, more intensive effort will have to be undertaken at 

locations that are accessible to hunters or wildlife managers.(312) 

The effort will have to be repeated periodically as the deer population will grow back to the same 

levels if the habitat conditions remain similar; it is not a one-time-only measure. 

Recreational hunters tend to focus on mature bucks rather than young animals or does, which is 

the least effective way to reduce the population size.(55) A change in regulations may be required 

to allow for greater quota, specifically for younger animals and does.(312,323) 

The number of hunters is declining, perhaps demanding a shift from recreational hunting to 

professional culling.(313,318)

Baiting in order to facilitate wildlife culling increases efficacy but is illegal in some areas, and it 

can lead to undesirable side effects such as increased risk of the spread of diseases, reduction in 

the consumption of natural foods and consequent changes in the ecosystem, population increase 

and consequent starvation, crowding, fighting and injuries of deer, deer domestication and 

habituation to unnatural foods and humans, decrease in hunter satisfaction, and increase in 

concerns of the nonhunting public.(323,324)

Costs 

The costs for a controlled hunt were estimated at $117 per deer killed. The cost of using 

professional sharpshooters was $108–121–194 per deer for conservation officers, park rangers, 

and police officers, respectively.(52) Others estimated these costs at $91–310 per deer.(287)
 128 

Guidelines 

No guidelines were identified in the literature review. 

WILDLIFE RELOCATION 

Wildlife relocation involves the capture, transport, and release of animals (mostly moving deer to 

another location). It is typically considered if population reduction is required but culling is not 

an option. 

At the Sea Pines residential area on Hilton Head Island, SC, a deer relocation experiment was 

conducted.(325) The relocated deer experienced relatively high mortality from capture-related 

causes, and 50 percent of the relocated deer dispersed from their release site.(325) 

Case Studies and Contacts 

For more information on a field test of the live-capture and small-scale relocation of urban deer 

on Hilton Head Island, SC, contact Jennifer Cromwell, United States Department of Agriculture, 

Wildlife Services, Moseley, VA, 23120, (804) 734-7739, jennifer.s.cromwell@aphis.usda.gov. 

Direct Benefits 

The relationship between deer population size and DVCs can be highly variable (see earlier 

discussion). Nonetheless, based on Doerr, Knapp and others, a certain percentage reduction in 

population size may result in a similar percentage reduction in DVCs.(52,53) However, reductions 

in population size of 50 percent or more may be hard to obtain, perhaps capping a potential 

reduction in DVCs at 50 percent or less.(52) The effectiveness can be seriously diminished if it is 

an open population that allows the individuals from neighboring populations to fill the gaps or 

that allows the relocated individuals to return.(325)

Indirect Benefits 

Benefits include reduced negative impacts from “overpopulation” on agricultural crops, 

silviculture, and natural vegetation.(55) 

Undesirable Effects 

With an open population or relocation over relatively short distances, individuals from 

neighboring populations may fill the gaps or a substantial portion of the relocated individuals 

may return to the original location, seriously limiting the effectiveness of this measure.(325) In one 

study, 50 percent of the relocated deer did not remain in their release area.(325)

The effort will have to be repeated periodically as the deer population will grow back to the same 

levels (growth, immigration, including of individuals that were relocated) if the habitat 

conditions remain similar; it is not a one-time-only measure. 

Relocated individuals tend to experience a lower survival rate and increased human-induced 

mortality, including from the capturing effort.(325,326) Relocation of deer can result in the spread 

of infectious diseases.(327) Wildlife relocation is, in general, not recommended.(328)
 129 

Relocated individuals may compete with individuals that are already present at the release site, 

or they may contribute to the growth and overpopulation at the release site and the negative 

effects associated with overpopulation.(55)

The effort may not be favored or accepted by the public, especially in areas that have a high 

degree of ecological integrity (“hands-off” approach).(57)

Costs 

The costs for relocation were estimated at $387 per relocated deer.(326) Others estimated these 

costs at $431 or $400–2,931 per deer.(287)

Guidelines 

No guidelines were identified in the literature review. 

ANTI-FERTILITY TREATMENT 

Anti-fertility treatment can reduce reproduction of deer. (See references 329, 330, 331, 332, and 

333.). This measure is typically considered or applied where killing (through hunting) is illegal 

(private lands, legislation) or impractical ((sub) urban areas, public pressure), where 

recolonization possibilities from elsewhere are limited (closed population), and where a 

relatively small deer population exists (e.g., 2000 or fewer breeding females). (See references 

330, 334, 335, 336, and 337.) Some drugs have shown to be effective for up to 1 or 2 years, but 

repeated application is often needed. The reversibility of anti-fertility treatment can be 

considered an advantage (if reproduction is necessary later) as well as a disadvantage (continuing 

treatment required).(330,338)

Modeling efforts have shown that sterilization in combination with hunting can control the 

population size of deer.(334,335) For the deer on Cumberland Island National Seashore, GA, (herd 

size 1,500 animals), the model predicted that the herd size could be controlled at 750 animals if 

200 sterilizations are done per year for the first 3 years, followed by 42 sterilizations per year for 

the following years).(334) Should the existing levels of hunting and predation continue, these 

numbers can be reduced to 81 (initial 3 years), but they would be higher for the following years 

(58 per year). Modeling by Seagle and Close showed that with contraception rates of less than 

50 percent of female deer, the population growth curve was less steep, but herd size was not 

reduced.(335) A minimal contraception rate of 50 percent was required to reduce the herd size. 

With contraception rates greater than 50 percent, substantial changes in population size were 

only observed after 5–10 years. Variability of the results was high, suggesting that it is difficult 

to detect population changes in the field.(335) Another modeling effort showed that a deer 

population could be reduced by 30–60 percent in 4–10 years if 25–50 percent of the fertile 

females were sterilized annually.(339) Models developed by Porter and others showed that with 

8 percent female dispersal, contraception would need to be effective in 32 percent of the females 

if the population were at about carrying capacity, and 68 percent if the population were at onehalf of carrying capacity.(320)

Results of a field test on a suburban white-tailed deer population in Irondequoit, NY, using 

immunocontraception suggest that the measure may be most practical when a population density 
 130 

between 30 and 70 percent of ecological carrying capacity is acceptable. However, it is only 

considered useful in relatively small and closed populations (≤ 200 females).(336) Walter and 

others captured and treated suburban female white-tailed deer in Connecticut with a 

contraceptive.(340) Baiting and capturing of the deer was more effective in spring than in fall. The 

study indicated that treatment of about 70 percent of the population was possible.(340) A capture 

and sterilization program for a white-tailed deer population in Cayuga Heights, NY showed that 

capture efforts had to be relatively high because the traps were not sex or age specific.(341)

Furthermore, the efficacy of the sterilization program was dramatically reduced because it was 

not a closed population.(341) 

Case Studies and Contacts 

For information on a field test using immunocontraception in a suburban white-tailed deer in 

Irondequoit, NY, contact Brent Rudolph, Department of Fisheries and Wildlife, Michigan State 

University, East Lansing, MI 48824, (517) 432-4943, rudolp13@msu.edu. 

For information on a field test using a contraceptive in a suburban white-tailed deer in 

Connecticut, contact David Walter, Oklahoma Cooperative Fish and Wildlife Research Unit, 

Oklahoma State University, 404 Life Sciences West, Stillwater, OK, 

74078, wdwalte@okstate.edu. 

For information on a field test using sterilization in a white-tailed deer population in Cayuga 

Heights, NY, contact Johnny Merrill, Cornell University, Department of Natural Resources, 

Fernow Hall, Ithaca, NY 14853, jam82@cornell.edu. 

Direct Benefits 

The relationship between deer population size and DVCs can be highly variable (see earlier 

discussion). Nonetheless, based on Doerr, Knapp and others, a certain percentage in reduction of 

population size may result in a similar percentage reduction in DVCs.(52,53) However, reductions 

in population size of 50 percent or more may be hard to obtain, perhaps capping the potential 

reduction in DVCs at 50 percent or less.(336) The effectiveness is seriously diminished if it is an 

open population that allows the individuals from neighboring populations to fill the gaps.(341)

Indirect Benefits 

Benefits include reduced negative impacts from “overpopulation” on agricultural crops, 

silviculture, and natural vegetation.(55) 

Undesirable Effects 

Fertility control and immunocontraceptives by some drugs disrupt normal reproductive behavior 

and can cause physical problems with the reproductive system, abscesses and inflammations, 

weight gain, changes in general behavior, and changes in the sex ratio in the herd.(342,343)

However, health problems and effects on social behavior may not always occur, or they may be 

minimal.(338)
 131 

The efforts will have to be repeated constantly in a population, and depending on the drug used, 

the same animals may have to be treated multiple times during their lives.(See references 330, 

334, 338, and 344.)

The effort is less effective, or not effective, when recolonization from elsewhere can occur (open 

population).(335)

The method may only be feasible for relatively small populations (200 or fewer females).(336)

Costs 

Walter and others calculated that $33,833 ($1,128 per treated deer) was required to treat 30 deer 

for 2 years (labor was 64 percent of the total budget).(340)

Guidelines 

No guidelines were identified in the literature review. 

HABITAT ALTERATION AWAY FROM THE ROAD 

Deer population density depends on the quality of their habitat. An abundance of food and cover, 

in combination with an absence of predators and hunting, allows for relatively high population 

densities. (See references 55, 57, 312, 313, 314, and 315.) In general, good feeding habitat for 

deer may include young forests (e.g., in harvested areas that have been replanted or that have 

naturally regenerated), agricultural lands (hay or alfalfa meadows, especially if they are fertilized 

and irrigated, and crop lands), lawns and gardens (including golf courses), and riparian habitat. 

Good cover is provided by forests or shrubland. When there is a matrix of good cover with good 

feeding habitat, deer population densities are typically relatively high. The size of the herd can 

be reduced through culling, relocation, or anti-fertility treatment, but if the habitat remains 

similar, deer densities will quickly return to their original levels, partly as the result of densitydependent fertility. Therefore habitat alterations that will limit the population density in certain 

areas can be considered. These measures may include reducing the amount of edge habitat by 

having larger patches of cover and feeding habitat or reducing the quality and quantity of the 

available food.(345) 

Reducing the quality of the available food may be achieved by certain mowing or cutting 

practices, allowing for natural succession to more mature forests (where applicable) with 

different grass-herb and shrub vegetation on the forest floor, and reducing or stopping irrigation 

and the use of fertilizers.(346) Reducing the quantity of the available food can be achieved by 

allowing the natural succession to more mature forests (where applicable) with less grass-herb 

and shrub vegetation on the forest floor, or making prime feeding habitat unavailable to the deer, 

e.g., through the use of wildlife fencing.(346,347)

Reducing the quality of the available food may only limit populations in relatively poor years, 

and stimulating attractive browse to lure animals away from croplands may only work on a small 

scale and affect primarily females and has to take into account the relative attractiveness of the 

foods available in the area (345,348,349) 
 132 

Some of the measures discussed above may take a long time to take effect, while other measures 

may require a change in land use practices. However, these types of measures would reduce the 

frequency and level of population culling, relocation, and anti-fertility treatment needed to 

reduce deer population density to an “accepted” level. 

Case Studies and Contacts 

For information regarding movements of female white-tailed deer in relation to timber harvests 

in the central Appalachians, contact Tyler Campbell, Warnell School of Forest Resources, 

University of Georgia, Athens, GA 30602, (706) 542-4280,tcampbell@smokey.forestry.uga.edu. 

For information on the effects of food or cover removal on spacing patterns and habitat use in 

roe deer (Capreolus capreolus), contact Sandro Lovari, Section of Behavioral Ecology, 

Ethnology and Wildlife Management, Department of Environmental Sciences, University of 

Siena, Via Mattioli 4, 53100, Siena, Italy, lovari@unisi.it. 

For information on changes in roe deer population density in response to forest habitat 

succession, contact Robin Gill, Forest Commission Res. Div., Alice Holt Lodge, Farnham, 

Surrey GU10 4LH, United Kingdom, robin.gill@forestry.gsi.gov.uk. 

Direct Benefits 

The relationship between deer population size and DVCs can be highly variable (see earlier 

discussion). Nonetheless, based on Doerr, and Knapp and others, a certain percentage in 

population size reduction may result in a similar percentage in DVC reduction.(52,53) However, 

reductions in population size of 50 percent or more may be hard to obtain, perhaps capping the 

potential reduction in DVCs at 50 percent or less.(336) The effectiveness of habitat alteration is 

less dependent on having a relatively small and closed population compared to population 

culling, relocation, and/or anti-fertility treatment. 

Indirect Benefits 

This WVC mitigation approach minimizes damage to agricultural crops and gardens and lawns. 

Undesirable Effects 

If the habitat is negatively affected on a large scale within a short time period, population control 

may be required to avoid potential starvation or dispersal in response to the reduction in habitat 

quality and availability. 

Costs 

Costs are expected to be highly variable depending on site-specific circumstances. No costs were 

identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 
133 

CHAPTER 8. MITIGATION METHODS THAT SEEK TO PHYSICALLY SEPARATE 

ANIMALS FROM THE ROADWAY 

This broad category of WVC mitigation strategies includes those that attempt to physically 

separate animals from the roadway. The specific mitigation measures reported on in this chapter, 

by broad category based on their intent, consist of the following: 

• Wildlife fencing. 

• Boulders in the right of way. 

• Long tunnels and bridges over landscape. 

• Wildlife underpasses and overpasses. 

WILDLIFE FENCING 

Fencing is one of the most commonly applied measures to separate wildlife from motorists.(3)

Wildlife fences in North America typically consist of 2.0–2.4-m (6.5–8-ft)-high wire mesh fence 

material (figure 42). Several types of fence material are used, but page wire or cyclone fence 

material is most common. The Utah Department of Transportation has painted wire mesh dark 

brown, which effectively camouflages the wire mesh. Wooden or metal fence posts are typically 

used, and the latter are particularly important when fencing over rock substrates. 
134 

Figure 42. Photo. Wildlife fence along Interstate 90 near Bozeman, MT (copyright: Marcel 

Huijser, WTI). 

Woods reported 94–97 percent reduction in ungulate-vehicle collisions along a fenced section of 

the Trans-Canada Highway.(350) Along the same road, Clevenger and others showed that fences 

were effective in reducing vehicle collisions with ungulates by 80 percent.(351) Clevenger and 

others also identified that WVCs were closer to fence ends than expected by chance; however, 

access points (gaps in the fence) were not hotspots for WVCs along the Trans-Canada Highway 

in Banff National Park, Alberta.(351) Dodd and others found that wildlife fencing in combination 

with underpasses reduced elk-vehicle collisions by 86.8 percent.(352) Reed and others reported an 

average reduction of 78.5 percent for deer vehicle accidents in Colorado, and Ward reported a 

reduction of greater than 90 percent for mule deer in Wyoming.(353,354) In Sweden, fencing 

reduced moose-vehicle collisions by 80 percent.(76) Boarman and Sazaki found that new or 

properly maintained fences significantly reduced mortality for several wildlife species, including 

the desert tortoise.(355) They found 93 percent fewer tortoise carcasses and 88 percent fewer 

vertebrate carcasses along a fenced section compared to an unfenced section of highway. In 

British Columbia, exclusion fencing (2.4 m (8 ft) high on both sides) was 97–99 percent 

effective at reducing accidents with large wildlife.(356) In Pennsylvania, Feldhamer and others 

determined that 2.7-m (8.9-ft)-high fence was more effective than the 2.2-m (7.2-ft)-high fence 

but that deer permeated both types of fences, and overall DVCs were not reduced.(294) They 

suggested that fencing may be effective if properly maintained to fix holes that people cut into it 

and to repair gaps that develop under the fence. They also suggest that the size of the openings in 

the woven wire mesh be decreased. 
135 

The effectiveness of electric fencing (ElectroBraidTM) in keeping deer off runways at airports 

was studied by Seamans and VerCauteren, and their results could be applicable to preventing 

deer from accessing short segments of highway.(357) The authors found that fencing as low as 

1.3 m (4.3 ft) was sufficient to exclude deer unless deer were pressured across it. Fences were 

highly effective (90 percent) when turned on and maintained. 

In a theoretical study investigating how full fencing (no wildlife crossings) with the intent of 

keeping wildlife off of roadways and reducing wildlife mortality might affect the long-term 

viability of animal populations, Jaeger and Fahrig modeled population responses to a range of 

scenarios.(358) Their models showed that when no fencing was in place, traffic mortality had a 

stronger effect on population viability than the effect of animals avoiding the road. The authors 

concluded that fencing could improve viability in populations with high road mortality. They 

discouraged the use of fencing (without crossing structures) when the population size was stable. 

Case Studies and Contacts 

For more information about wildlife fencing in combination with wildlife overpasses and 

wildlife underpasses on the Trans-Canada Highway in Banff National Park, Canada, contact 

Anthony Clevenger, Western Transportation Institute, Montana State University, 

P.O. Box 174250, Bozeman, MT 59717-4250, (403) 609-2127, Tony.Clevenger@pc.gc.ca. 

For more information about wildlife fencing and underpasses along State Route 260 in Arizona, 

contact Norris Dodd, Wildlife Research Biologist, Arizona Game and Fish Department, Research 

Branch, P.O. Box 2326, Pinetop, AZ 85935, (928) 368-5675, doddnbenda@cybertails.com. 

For information about wildlife fencing along U.S. Highway 93, Flathead Indian Reservation, 

Montana, contact Pat Basting, Montana Department of Transportation, (406) 523-

5872, pbasting@mt.gov. 

For an evaluation of ElectroBraidTM fencing, contact Thomas Seamans; Wildlife Service, USDA, 

National Wildlife Resource Center, Ohio Field Station, Sandusky, OH 44870, 

thomas.w.seamans@usda.gov. 

Direct Benefits 

Depending on the species concerned, the type of fencing, and whether safe crossing 

opportunities are provided, wildlife fencing may reduce the number of WVCs 80–99 percent. It 

is important to note, however, that these reductions were obtained where wildlife fencing was 

used in combination with wildlife overpasses and/or wildlife underpasses. If safe crossing 

opportunities are not provided for, or if they are too few, too small or too far apart, animals are 

more likely to break through the wildlife fence, reducing the effectiveness of the wildlife 

fencing. 

Indirect Benefits 

Wildlife fences help keep pedestrians away from the travel lanes with fast-moving traffic. 
136 

Undesirable Effects 

Wildlife fences, when installed correctly, form a nearly impermeable barrier to large mammals. 

While this can nearly eliminate collisions with large mammals or at least reduce the number of 

collisions substantially, wildlife fences result in several unintended side effects, for example: 

• Animal movements across the road are blocked or nearly completely blocked, which 

increases the barrier effect of the road, disrupting daily, seasonal, and dispersal 

movements and potentially reducing the population survival probability of the species 

concerned. The species affected may include species that are not a safety threat or that 

may not have a population in the immediate vicinity of the transportation corridor. 

Therefore, absolute barriers, such as wildlife fencing, should always be accompanied 

with safe crossing opportunities. 

• Animals are more likely to break through the wildlife fencing if safe crossing 

opportunities are not provided or if they are too few, too small, or too far apart. Even if 

safe crossing opportunities have been provided for, animals may still end up in between 

the fences, caught in the transportation corridor, and these animals may pose a safety risk 

and expose the species concerned to road mortality after all. Animals may end up in 

between the fences around fence ends, digging under the fence (coyotes slipped beneath 

the fence along the Trans-Canada Highway in Banff National Park), through gaps in the 

fence, or they may be able to climb the fence. Therefore, absolute barriers, such as 

wildlife fencing, should always be accompanied with escape opportunities for animals 

that end up in between the fences. 

• Animals can and do cross the road where fences end. In some cases it can result in a 

concentration of AVCs at fence ends (Norris Dodd, Arizona Game and Fish Department, 

personal communication).(351) Therefore, consideration should be given to measures that 

mitigate a potential concentration of WVCs at fence ends. 

• Wildlife fencing can have a negative impact on landscape aesthetics; many people 

perceive tall wildlife fences as ugly. 

• Wildlife fencing may pose a direct or indirect mortality risk for certain species. Large 

mammals may get tangled up in the fence, or fences may injure them, potentially 

resulting in a slow death. In addition, wildlife fences may also be exploited by predators 

when pursuing prey. After the addition of two lanes on the Trans-Canada Highway and 

installation of fencing that cut off escape terrain for bighorn sheep, coyotes learned to 

stampede sheep into the fence. More than 30 sheep were killed this way until a mitigation 

measure was put in place (discussed later). In addition, wolves, bears, and other predators 

have also occasionally been seen running prey species into the wildlife fences.(359)

Finally, birds may collide with fences and die.(360,361)

• Access roads to the main road require a disruption of the wildlife fencing, resulting in an 

opening that has to be mitigated in order to avoid animals getting caught inside the fences 

along the transportation corridor. 
137 

• Access for people (hiking, biking, fishing) may be blocked by wildlife fencing. 

Wildlife underpasses and overpasses are tunnels and vegetated bridges designed for wildlife to 

allow them to cross the road. In addition, wildlife jump-outs are usually integrated with wildlife 

fencing. These features allow animals that do manage to cross the fence to escape from the 

fenced road and right of way. Other potential solutions for the unintended side effects described 

above are described in the next section “Addressing Undesirable Effects of Wildlife Fencing.” 

Costs 

Wildlife fencing (2.4 m (8 ft) high) in Banff National Park, Alberta cost Can$30 per meter 

(Can$9 per ft) (one side of highway) during the phase 3A Trans-Canada Highway expansion in 

1997 (Terry McGuire, Parks Canada, personal communication). For the entire 18-km section of 

highway, fencing both sides cost roughly Can$1,000,000. ElectroBraidTM fencing used in the 

study by Seamans and VerCauteren consisted of five-rope strands at 25 cm (9.7 inches) and cost 

$9 per meter ($2.7 per ft).(357) 1.2-m (4-ft)-high 5-BraidTM ElectroBraidTM Deer Exclusion Fence 

is advertised at $4,300 per km ($7,000 per mi), while 1.5-m (5-ft)-high, 5-BraidTM 

ElectroBraidTM Moose Exclusion Fence is advertised at $4,750 per km ($7,500 per mi).(362)_

Sielecki compared the benefits to costs of fencing over different time spans (20–30 years) and 

given different levels of potential damage prevented. He determined that benefits of the wildlife 

fencing outweighed potential costs in 12 of 16 cases.(356) Fencing in his study ranged from 

Can$40,000–80,000 per km. 

The cost of wildlife fencing along U.S. Highway 93 on the Flathead Reservation in Montana 

varied depending on the road section concerned: $26, $38, or $41 per m ($7.9, $11.6, or 

$12.5 per ft) (Pat Basting, Montana Department of Transportation, personal communication). A 

finer mesh fence was dug into the soil and attached to the wildlife fence for some fence sections 

at a cost of $12 per m ($6.7 per ft) (Pat Basting, Montana Department of Transportation, 

personal communication). 

Fencing could be impractical in dense vegetation areas, where there is little or no public roadside 

right of way. 

Guidelines 

For large mammals and particularly ungulate species, the standard height of wildlife fencing is 

currently 2.4 m (8 ft). When targeting specific fauna of smaller size, lower fence heights and 

more customized designs are generally used.(355,363,364) To keep some climbing species (cougars, 

bears) from scaling, wildlife fences can be made higher, the mesh size can be made smaller, and 

outriggers or overhangs can be incorporated into the design.(365,366) Some testing of these fences 

has taken place in captive settings, but they have not been objectively tested in the field. Fencing 

should also be tied to the ground or buried into the ground, depending on the target species and 

soil characteristics. If properly installed, fence material (wire and posts) should last 20 years or 

more without integral replacement (Terry McGuire, Parks Canada, personal communication).(367)

However, regular inspection for gaps and other problems is required.(368) 
138 

Regular fence maintenance is critical in order to keep the fence functioning properly. Earth 

slumping on hill slopes, inadequate installation techniques resulting in gaps between ground and 

fence bottom, and breaches of the fence by the public (e.g., hunters, snowmobile operators) 

allow animals to gain entry to the right of way. Fence maintenance is a major concern because 

priorities and budgets change over time. Fence maintenance is usually neglected shortly after 

construction; meanwhile fence damage and gaps are a recurrent problem. 

ADDRESSING UNDESIRABLE EFFECTS OF WILDLIFE FENCING 

Absolute barriers such as wildlife fences increase the barrier effects of a road, disrupting daily, 

seasonal, and dispersal movements and potentially reducing the population survival probability 

of the species concerned. The species affected may include species that are not a safety threat or 

that may not even have a population in the immediate vicinity of the transportation corridor. 

Therefore absolute barriers, such as wildlife fencing, should always be accompanied by safe 

crossing or escape opportunities for wildlife. The specific mitigation measures reported on in this 

section, by broad category based on their intent, consist of the following: 

• Create gaps in fencing. 

• Install wildlife underpasses and overpasses. 

• Provide escape opportunities for wildlife stuck in the right of way using: 

o Jump-outs or escape ramps. 

o One-way gates. 

• Mitigate WVCs at fence ends using: 

o Boulders between fence and roadway. 

o Animal detection systems. 

• Improve landscape aesthetics of wildlife fencing. 

• Reduce wildlife mortality risk of fencing. 

• Mitigate gaps in fencing at access roads using: 

o Gates. 

o Cattle or wildlife guards. 

Despite the fact that the primary intention of the various measures described in this section is to 

mitigate undesirable side effects of absolute barriers, some of the measures can also help further 

reduce WVCs while others may lead to an increase in WVCs. This is noted in the “direct 

benefits” and “undesirable effects” sections of the individual measures. 
139 

SAFE CROSSING OPPORTUNITIES: GAPS IN FENCE 

Gaps in fences on opposite sides of the road allow animals to cross the road. In most cases such 

gaps are accompanied with wildlife warning signs, crosswalks for wildlife, wildlife warning 

signs in combination with mandatory or advisory speed limit reductions, or animal detection 

systems. Along SR 260 near Payson, AZ, a gap in an electric fence has been combined with an 

animal detection system (David Bryson, Electrobraid Fence Ltd., personal communication; 

Norris Dodd, Arizona Game and Fish Department, personal communication). 

A system of wildlife fences and gaps was installed to reduce vehicle collisions with mule deer 

(Odocoileus hemionus) along a two-lane and divided four-lane highway in northeastern Utah.(41)

The gap had warning signs for motorists, and a crosswalk was painted on the road surface as an 

additional sign for motorists. Road mortality was reduced by 42.3 percent (four-lane highway) 

and 36.8 percent (two-lane highway) compared to the expected road mortality. However, 

statistical significance of this reduction could not be demonstrated. 

Similar to wildlife fences, median barriers can be an absolute or partial barrier to certain 

species.(310) In some cases gaps have been created in the median barrier to allow animals to cross 

the road. However, the effectiveness of these gaps has largely been untested.(310) 

Case Studies and Contacts 

For information on gaps in wildlife fencing with warning signs and crosswalk, contact John 

Bissonette, Utah Cooperative Fish Wildlife Research Unit, Utah State University, Logan, UT, 

84322-5290, (435) 797-2511, john.bissonette@usu.edu. 

An example of a gap in a wildlife fence accompanied by wildlife warning signs and an advisory 

speed limit reduction in The Netherlands is shown in figure 43. 

An example of a gap in a wildlife fence combined with an animal detection system and 

accompanying wildlife warning signs and an advisory speed limit reduction in The Netherlands 

is shown in figure 44. 
140 

Figure 43. Photo. Gap in a wildlife fence accompanied by wildlife warning signs and 

advisory speed limit reduction, The Netherlands (copyright: Marcel Huijser). 

Figure 44. Photo. Gap in a wildlife fence combined with an animal detection system, 

wildlife warning signs, and advisory speed limit reduction, The Netherlands (copyright: Marcel 

Huijser). 
141 

Direct Benefits 

Wildlife fences may reduce road mortality by 80–99 percent but may increase the barrier effect 

of the road. Gaps in the wildlife fence allow animals to cross the road, but since they cross at 

grade, mortality occurs, reducing the effectiveness of the wildlife fence. Data are not available 

on the roadkill that occurs at a gap with or without warning signs, but a gap in a wildlife fence 

that is combined with wildlife warning signs and a crosswalk reduced the effectiveness of the 

wildlife fence from 80–99 percent to 42.3 percent (four-lane highway) and 36.8 percent (twolane highway).(41) Animal detection systems have been used at gaps in wildlife fences, but there 

are no data on the effectiveness of this measure in combination with a gap in a fence. As a 

standalone mitigation measure, however, animal detection systems may reduce collisions with 

ungulates by 82 percent on average.(197)

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

At gaps in fences, animals cross the road at grade, exposing the drivers and wildlife to potential 

collisions. This may reduce the effectiveness of the wildlife fence, but this depends on what type 

of warning signals are presented to drivers at the gap in the fence. No data have been located 

about the risk of gaps that have static warning signs, but the available data for animal detection 

systems suggest that a gap with an animal detection system may reduce the effectiveness of the 

wildlife fencing from 87 percent (on average) to 82 percent. In addition, once through a gap, 

animals may wander along the road or in the right of way, becoming trapped in between the 

wildlife fences, exposing the drivers and wildlife to other potential collisions. Measures that 

allow animals to escape from the road and right of way should be implemented (see further 

information later in this section). 

Costs 

The costs of crosswalks across a two-lane road and a four-lane road (excluding wildlife fencing 

and escape from right of way measures) were reported at $15,000 and $28,000, respectively.(41)

The estimated cost of animal detection systems at a gap in the fence is $50,000 (including 

installation and fence).(197)

Guidelines 

See Lehnert and Bissonette for guidelines.(41) 

SAFE CROSSING OPPORTUNITIES: WILDLIFE UNDERPASSES AND OVERPASSES 

Wildlife underpasses and overpasses are used extensively by a wide array of species to get from 

one side of the road to the other side (figure 45 through figure 47). (See references 294, 368, 369, 

and 370.) The performance of these structures in reducing WVCs and creating crossing 

opportunities is linked to associated wildlife fencing that keeps animals off the road and funnels 
142 

them toward the wildlife overpasses and underpasses.(368) In some cases wildlife fencing is only 

installed over relatively short distances funneling wildlife towards a crossing structure.(371) The 

use of wildlife fencing was found to increase the use of underpasses by elk (Cervus elaphus) and 

increase the permeability of a road substantially.(352) In other cases wildlife underpasses and 

overpasses have no or very limited wildlife fencing, making them the primary measure to reduce 

WVCs on short road sections. 

The location, type, and dimensions of wildlife crossing structures must be carefully planned with 

regard to the species and surrounding landscape. For example, grizzly bears, deer and elk tend to 

use wildlife overpasses to a greater extent than wildlife underpasses, while black bears and 

mountain lions use underpasses more frequently than overpasses.(368) In addition, different 

species use different habitats, influencing their movements and where they want to cross the 

road. Other factors that should be considered are the vegetation in the direct vicinity of the 

crossing structure (cover), co-use by humans, and the time it takes for animals to learn the 

location of the structures and to learn that they are safe to use. 

In North America, wildlife overpasses are far less common than in Europe. Therefore there are 

few experiences with tunnels and wildlife overpasses, as only six of the latter are found in North 

America and only two in Banff have been studied with regard to their effectiveness in terms of 

reducing road mortality and allowing for safe crossing opportunities. 

Figure 45. Photo. Wildlife underpass along U.S. Highway 93 on the Flathead Indian 

Reservation, MT (copyright: Marcel Huijser, WTI). 

The use of wildlife underpasses and overpasses depends on many parameters, including their 

location in the landscape, their dimensions, the habitat surrounding the structures, human co-use, 
143 

and the time since installation (learning curve for the animals).(368) Furthermore, different species 

have different preferences. 

Figure 46. Photo. Wildlife overpass in Banff National Park, Alberta, Canada (copyright: 

Marcel Huijser). 

Figure 47. Photo. Underpass in southern Florida that allows for ecosystem processes 

(hydrology) as well as wildlife use, including the Florida panther (copyright: Marcel Huijser). 
144 

Case Studies and Contacts 

For information on crossing structures in Banff National Park, contact Tony Clevenger, Western 

Transportation Institute, (403) 609-2127, tony.clevenger@pc.gc.ca. 

For information on Florida crossing structures, contact Melissa Foster, University of Florida, 

Gainesville, FL. 

For more information on wildlife underpasses and one wildlife overpass along U.S. Highway 93 

on the Flathead Indian Reservation in Montana and on one wildlife overpass across Montana 

Highway 83 near Salmon Lake (in planning, under construction and completed), contact Pat 

Basting, Montana Department of Transportation, (406) 523-5872, pbasting@mt.gov. 

For more information about wildlife fencing and underpasses along State Route 260 in Arizona, 

contact Norris Dodd, Wildlife Research Biologist, Arizona Game and Fish Department, Research 

Branch, P.O. Box 2326, Pinetop, AZ 85935, (928) 368-5675, doddnbenda@cybertails.com. 

Direct Benefits 

Wildlife overpasses and underpasses increase the effectiveness of wildlife fencing or other 

barriers alongside the road in reducing WVCs. If no safe crossing structures are provided, 

animals are more likely to break through the wildlife fencing (or other barrier) and thereby 

reduce the effectiveness of the wildlife fencing. 

Indirect Benefits 

Wildlife overpasses and underpasses provide crossing opportunities for wildlife, which are 

needed to mitigate habitat fragmentation effects of roads and maintain viable populations over 

the long term. 

Undesirable Effects 

If overpasses are not designed properly, wildlife that are reluctant to use the structure may try to 

breach the fence and cross the highway. 

Costs 

Costs vary widely depending on dimensions of underpass structures. Some estimated costs for 

different underpass structures are box culverts (3.0 m (9.8 ft) high by 2.5 m (8.2 ft) wide) = 

$Can2,800 per m ($854 per ft) length, elliptical culverts (4 m (13 ft) high by 7 m (23 ft) wide) = 

$Can5,400 per m ($Can1,646 per ft) length, open span bridge underpass (13 m (43 ft) wide by 

5 m (16 ft) high) = $Can55,000 per m length (Terry McGuire, Parks Canada, unpublished data). 

In The Netherlands, large underpasses (7–10 m (23–33 ft) wide) are estimated to cost €30,000–

50,000 per m.(372)

Tunneling and overpass structures can cost approximately $Can33,650 per m ($Can10,259 per 

ft) for a 50-m (164-ft)-wide overpass to $Can119,300 for a 27-m (88-ft)-wide and 200-m 
145 

(656-ft)-long tunnel (Terry McGuire, Parks Canada, unpublished data). Actual overpasses were 

estimated at Can$1,750,000 (Anthony P. Clevenger, Western Transportation Institute, Montana 

State University, personal communication). 

A proposed overpass across Montana Highway 83 near Salmon Lake (two-lane road) is 

estimated to cost $1,500,000–2,400,000. 

The costs for seven wildlife overpasses in The Netherlands ranged between €1,400.000 and 

€5,600,000.(372)

Guidelines 

Recommended minimum dimensions for underpasses and overpasses have been suggested for 

some ungulate species, but the needs of wide-ranging species are vague at best.(166) The most 

comprehensive guidelines for designing wildlife crossing structures, including most below-grade 

crossing structures, can be found in Iuell.(373) This European handbook draws from the wealth of 

European experience building a variety of wildlife crossings. Guidelines for different wildlife 

taxa in Europe and North America can be found in Iuell, Foster and Humphrey, Clevenger and 

Waltho, Clevenger and Waltho, and Kruidering and others. (See references 166, 372, 373, 374, 

and 375.) The last publication includes cost estimates for a range of types of crossing structures. 

Guidelines for wildlife crossings are being developed from NCHRP 25 to 27 and will available 

in 2008. 

If large species are involved that are sensitive to human disturbance, or if multiple habitats have 

to be provided for on an overpass, wildlife overpass structures are generally recommended to be 

at least 50–70 m (164–230 ft) wide. Further rationale for this width is provided by Pfister and 

others, who showed that the increase in use of wildlife overpasses increases linearly until a width 

of about 50 m (164 ft) at which point the increase in wildlife use starts to taper off.(376) 

ESCAPE OPPORTUNITIES FROM RIGHT OF WAY 

Animals may end up in between fences or other barriers placed along the transportation corridor, 

posing a safety risk and exposing the species concerned to road mortality. Therefore, absolute 

barriers, such as wildlife fencing, should always be accompanied with escape opportunities for 

animals that have ended up in between the fences. (See references 82, 294, 370, and 377.) 

ESCAPE OPPORTUNITIES FROM RIGHT OF WAY: JUMP-OUTS OR ESCAPE 

RAMPS 

Jump-outs or “escape ramps” are sloping mounds of soil placed against a backing material 

approximately 1.5 m (5 ft) in height and constructed on the right-of-way side of the fence (figure 

48). The highway fence (2.4 m (8 ft)) is lowered at the ramp site and forms an integral part of the 

jump-out that allows deer or other species to jump to the safe side of the fence. The vertical drop 

off on the back side of escape ramps is designed to preclude deer from gaining access to the right 

of way from the nonhighway side of the fence. Deer and elk are the most common users of jumpouts along the Trans-Canada Highway in Banff National Park, but moose and bighorn sheep 

have also used these structures (Bruce Leeson, personal communication). 
146 

Figure 48. Photo. Jump-out or escape ramp along U.S. Highway 93 on the Flathead Indian 

Reservation, MT (copyright: Marcel Huijser, WTI). 

Bissonette and Hammer studied the effectiveness of earthen escape ramps (jump-outs) and oneway gates along a fenced section of U.S. 91 and U.S. 40 in northern Utah.(82) The 2.4-m (8-ft) 

fence was not 100 percent effective, due to human vandalism and gaps under the fence, so 

additional measures were necessary to help get deer off the highway. The authors noted peaks in 

DVCs in spring and fall, and noted that DVCs declined after installation of jump-outs. Jump-outs 

were eight to eleven times more effective than one-way gates. The authors calculated that if the 

ramps offset even 2 percent of deer mortality, they would be considered cost effective within 1 to 

2 years. They recommended jump-outs instead of one-way gates and determined that (with 

fencing) these are effective mitigation measures at removing deer from highway rights of way 

and minimizing accidents with motorists. Clevenger and others documented use of jump-outs by 

deer, elk, and coyote on the Trans-Canada Highway.(378)

Case Studies and Contacts 

For information on jump-outs along U.S. Highway 93, Flathead Indian Reservation, Montana, 

contact Pat Basting, Montana Department of Transportation, (406) 523-5872, pbasting@mt.gov. 

For more information on field tests with escape ramps in Utah, contact John Bissonette and 

Mary Hammer, USGS Utah cooperative Fish and Wildlife Research Unit, Department of 

Fisheries and Wildlife, College of Natural Resources, Utah State University, Logan, UT 84322-

5290, (435) 797-2511, john.bissonette@usu.edu; and hammer@wra-ca.com. 
147 

For information on field observations from jump-out use along the Trans-Canada Highway, 

Canada, contact Tony Clevenger, Western Transportation Institute, Montana State University, 

P.O. Box 174250, Bozeman, MT 59717-4250, (403) 609-2127, Tony.Clevenger@pc.gc.ca. 

Direct Benefits 

Using jump-outs or escape ramps along two fenced road sections reduced collisions by 

28.6 percent on average.(82)

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

If the jump-outs are not high enough, animals may jump up and end up in the right of way in 

between the fences. On the other hand, if jump-outs are too high, animals will not use them to 

escape from the transportation corridor. Furthermore, jump-outs need to be well away from the 

travel lanes and recovery zone to avoid cars running into them. 

Costs 

Reported costs for one jump-out include $11,000 and $6,250 (Pat Basting, Montana Department 

of Transportation, personal communication).(82)

Guidelines 

The wall of a jump-out must be just high enough to discourage wildlife from trying to jump up 

into the right of way, but not so high that they discourage wildlife from jumping off. This is a 

delicate balance, and the optimal height of the jump-out is likely to be influenced by the species 

that is expected to breach the fence most often and the nature of the terrain surrounding the 

jump-outs (e.g., up slope or down slope). To prevent injury to the animals that jump out, the 

landing spot at the bottom of the jump-out should consist of loose soil or other soft material 

(Bruce Leeson, personal communication). Where bears are present, the walls must be smooth to 

prevent them from climbing into the right of way (Bruce Leeson, personal communication). 

Furthermore, it is thought to be best for jump-outs to be positioned in a set-back in the fence, in 

an area protected with tree cover, where animals may calm down and have time to decide 

whether to jump off the jump-out (Bruce Leeson, personal communication). A short fence on the 

jump-out itself, perpendicular to the road and the right-of-way fence, may also help guide 

animals to the jump-outs. For additional guidelines see Bissonette and Hammer.(82) 

ESCAPE OPPORTUNITIES FROM RIGHT OF WAY: ONE-WAY GATES 

One-way gates allow animals to enter from the road side and go through the fence, providing a 

possible opportunity for escape from the transportation corridor. Gates (figure 49 and figure 50) 

have been built for different species, including elk, deer, and the Eurasian badger.(82,370,372) Reed 

and others found one-way gates relatively effective for deer, whereas Lehnert found that only 

17 percent of the deer that approached the gates ended up using them.(377,379) In general one-way 
148 

gates are no longer recommended as wildlife can learn how to use them to get into the right of 

way, sometimes aided by hikers, fisherman, equestrians, and bikers who propped and tied the 

gates open (Bruce Leeson, personal communication).(368) In Banff National Park, Canada, an elk 

herd not only learned how to go through the gate the “wrong way,” but they also destroyed the 

gate within a week after they learned how to enter the gate from the wrong side (Bruce Leeson, 

personal communication). In the same area, coyotes learned to crawl through the tines to feed on 

mice that became more abundant in the right of way now that it was no longer grazed by 

ungulates (Bruce Leeson, personal communication). At another location, at least one elk has 

been observed taking a gate “out” as the gate was too small for its body size (Monique 

DiGiorgio, Southern Rockies Ecosystem Project, personal communication), and at least one 

moose has been observed getting stuck with its antlers and damaging its velvet (Rick Sinnott, 

Alaska Fish and Game, personal communication). Finally, jump-outs appear more effective than 

one-way gates in allowing ungulates to escape from the right of way.(82) 

Figure 49. Photo. One-way elk gate in British Columbia, Canada (copyright: Marcel Huijser). 
149 

Figure 50. Photo. One-way Eurasian badger gate, The Netherlands (copyright: Marcel 

Huijser). 

Case Studies and Contacts 

For more information on one-way gates for deer in Utah, contact John A. Bissonette, Utah 

Cooperative Fish Wildlife Research Unit, Utah State University, Logan, UT, 84322-5290, (435) 

797-2511, john.bissonette@usu.edu.

(82)

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

There are undocumented reports that animals tried to back up in elk gates, got stuck, wounded 

themselves, and died. 

Costs 

Estimated costs were reported at $8,000 per one-way gate.(82)
150 

Guidelines 

See Bissonette and Hammer for guidelines.(82) 

MITIGATION FOR FENCE ENDS: BOULDERS BETWEEN FENCE AND ROADWAY 

To discourage ungulate species from entering the fenced sections of the Trans-Canada Highway 

in Alberta, Canada, rock impediments or boulder fields were placed at the ends of the fence 

between the roadway and the fence, as shown in figure 51.(378) Boulders roughly the size of 

bowling balls were laid out uniformly to create a boulder field. The boulders are thought to 

discourage animals, especially ungulates, from walking on them. 

The boulder field at Dead Man’s Flats wildlife underpass along the Trans-Canada Highway east 

of Canmore, Alberta, is 100 m (328 ft) long with the width varying from about 8–20 m 

(26–66 ft), depending on how close the fence is positioned to the roadway, with the boulders 

extending right from the edge of pavement up to the fence (Bruce Leeson, personal 

communication) (figure 51). In addition, a 19-m (62-ft)-wide strip of boulders was placed in the 

median. The boulders are subangular, quarried rock, ranging in size from 20 to 60 cm 

(7.8–23.6 inches) (about 75 percent are larger than 30 cm (11.8 inches)). The boulder apron, at a 

depth of about 40–50 cm (15.7–19.7 inches), is installed on geofabric on subexcavated smoothed 

ground. The boulders project about 20–30 cm (7.8–11.8 inches) above the local ground surface 

(Bruce Leeson, personal comment). 

Case Studies and Contacts 

For information on the use of boulders between the fence and roadway at fence ends along the 

Trans-Canada Highway in Banff National Park, contact: Bruce Leeson, Bruce F. Leeson 

Environmental Consulting Co., 10011 5th St. S.E., Calgary, Alberta, Canada T2J 1L4, 

(403) 271-7235 (desk), (403) 869-8180 (cell), bfleeson@shaw.ca; and Tony Clevenger, Western 

Transportation Institute, Montana State University, P.O. Box 174250, Bozeman, MT 59717-

4250, (403) 609-2127, Tony.Clevenger@pc.gc.ca. 

Direct Benefits 

Clevenger and others found that the combination of the boulder field and wildlife fencing were 

effective in reducing WVCs. Six DVCs occurred prior to fencing (and boulder field installation), 

while only two occurred after fencing.(378) The boulders were believed to be an effective 

deterrent in keeping ungulates from wandering in between the fences.(378)
151 

Figure 51. Photo. The boulder field at the fence end at Dead Man’s Flats along the TransCanada Highway east of Canmore, Alberta, Canada (copyright: Bruce Leeson). 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

In areas of regular snowfall, the boulder fields become covered with snow, which allows 

ungulates to travel across them. There may be some motorist safety issues for some states by 

having an obstruction (and hazard) within the clear zone. In Alberta these safety issues were 

addressed by placing a guard rail at the road edge. 

Costs 

The material and labor for the installation of boulders at the fence end at Dead Man’s Flats 

wildlife underpass along the Trans-Canada Highway east of Canmore, Alberta, was estimated to 

cost Can$65,000 (installed in 2005, cost estimate for 2007) (Bruce Leeson, personal 

communication). 

Guidelines 

The boulder field begins at the fence end, sits on the margin of the paved edge of the highway, 

and is approximately 15 m (49 ft) wide. The length of the field starting at the fence ends is 

approximately 20–25 m (66–82 ft). 
152 

MITIGATION FOR FENCE ENDS: ANIMAL DETECTION SYSTEMS 

Animals may cross the road where fences end, which can in some cases result in a concentration 

of AVCs. In Arizona, an experiment is currently being conducted with animal detection systems 

at fence ends to mitigate a concentration of deer and elk vehicle collisions (Norris Dodd, Arizona 

Game and Fish Department, personal communication). 

Case Studies and Contacts 

For information on animal detection systems at fence ends, contact Norris Dodd, Wildlife 

Research Biologist, Arizona Game and Fish Department, Research Branch, P.O. Box 2326, 

Pinetop, AZ 85935, (928) 368-5675, doddnbenda@cybertails.com. 

Direct Benefits 

The benefits of using animal vehicle detection systems at fence ends are unknown, but as a 

standalone mitigation measure, animal detection systems can reduce collisions with large 

ungulates by 82 percent.(197) The application of animal detection systems at fence ends can be 

expected to result in a similar reduction in WVCs, but data on effectiveness are relatively scarce 

and may vary. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

No cost were identified in the literature review. 

Guidelines 

See Huijser and others for general design considerations.(197) 

LANDSCAPE AESTHETICS OF WILDLIFE FENCING 

Wildlife fencing can have a negative impact on landscape aesthetics; many people perceive tall 

wildlife fences as ugly. A potential solution is to replace wildlife fencing with large boulders (see 

earlier) to discourage ungulates from entering the right of way. However, there are no data on 

how effective large boulders are at reducing WVCs. Other approaches have been tried or are in 

the process of being tried to make the fence less visible by installing fences behind trees and 

painting the fence brown or green so that it blends in better with the background 

(Terry McGuire, Parks Canada, personal communication). 
153 

Case Studies and Contacts 

For details on installation of fences behind trees along Trans-Canada Highway, contact 

Terry McGuire, Parks Canada, terry.mcguire@pc.gc.ca. 

For information on future experiments with green instead of metal-colored fencing along the 

Trans-Canada Highway, contact Terry McGuire, Parks Canada, terry.mcguire@pc.gc.ca. 

Direct Benefits 

Colored fencing has no known additional impact on WVCs beyond the standard colored wildlife 

fencing. 

Indirect Benefits 

Less visible fences have reduced impact on landscape aesthetics. 

Undesirable Effects 

As fencing becomes less visible, the risk of wildlife colliding with it may increase (see “Reduce 

Mortality Risk of Wildlife Fencing” below). 

Costs 

Fencing costs remain similar to standard wildlife fencing (see earlier) (Terry McGuire, Parks 

Canada, personal communication). 

Guidelines 

Similar to standard wildlife fencing (see earlier). 

REDUCE MORTALITY RISK OF WILDLIFE FENCING 

Wildlife fencing may pose a direct or indirect mortality risk for certain species through 

entangling or wounding animals, or because predators run prey species into the wildlife fence. 

Parks Canada installed a green “curtain” on the wildlife fence along a section of the TransCanada Highway, which enabled the sheep to see the fence and veer away from it 

(Terry McGuire, Parks Canada, personal communication). Chestnut paling has been used in deer 

exclusion fences to make them more visible to birds, especially capercaille (Tetrao 

urogallus).(361)

Case Studies and Contacts 

For details on the green curtain on the wildlife fence used to increase visibility for bighorn sheep 

along the Trans-Canada Highway in Banff National Park, contact Terry McGuire, Parks 

Canada, terry.mcguire@pc.gc.ca. 
154 

For information on chestnut paling used in a deer exclusion fence to increase visibility for birds, 

especially capercaille, contact: John Dobson, The Croft, Balmoral, Ballater, Scotland, 

AB35 5TX, forestry@balmoralestate.co.uk. 

Direct Benefits 

There is no additional benefit from this alteration that further reduces WVCs as compared to the 

basic WVC mitigation measure. 

Indirect Benefits 

Wildlife mortality as a result of the presence of the fence is decreased. 

Undesirable Effects 

Increased visibility of the fence may negatively impact landscape aesthetics. 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 

GAPS CAUSED BY ACCESS ROADS 

Access roads to the main road require a disruption of the wildlife fencing, resulting in an opening 

that has to be mitigated in order to avoid animals getting caught inside the fences along the 

transportation corridor. The following sections describe potential solutions to this problem. 

GAPS CAUSED BY ACCESS ROADS: GATES 

Gates can be opened when leaving or accessing the main road. This approach is an 

inconvenience to drivers, as they have to stop and get in and out of their vehicle. Gates are 

normally only installed at access roads that have very low traffic volume. 

Case Studies and Contacts 

For information on gates along U.S. Highway 93, Flathead Indian Reservation, MT, contact: 

Pat Basting, Montana Department of Transportation, (406) 523-5872, pbasting@mt.gov. 

Direct Benefits 

The use of gates results in no further reduction in collisions compared to an undisrupted wildlife 

fence (presuming the gates are closed by users). 
155 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

Gates are an inconvenience to drivers, and they may potentially increase WVCs if they are left 

open. 

Costs 

Costs for single- and double-panel gates along U.S. Highway 93 on the Flathead Indian 

Reservation, MT, were $300–360 and $350–550, respectively (Pat Basting, Montana Department 

of Transportation, personal communication). 

Guidelines 

No guidelines were identified in the literature review. 

GAPS CAUSED BY ACCESS ROADS: CATTLE OR WILDLIFE GUARDS 

Cattle or wildlife guards are designed to discourage wildlife, especially ungulates, from walking 

through a gap in the fence (figure 52). However, standard cattle guards may be easily passable by 

Florida Key deer and mule deer and dangerous to pedestrians and cyclists, and special designs 

may be needed (for example, those developed for the Florida Key deer).(380,381) In some cases, 

such as along a side road of the Trans-Canada Highway in Banff National Park, Canada, a 

wildlife guard has also been put under electric current to discourage bears from walking across it. 

An electrified mat across an access road has also been used to discourage ungulates from using a 

gap in a fence for an access road to approach a larger road with higher traffic volume and vehicle 

speeds (David Bryson, Electrobraid Fence Ltd, personal communication). 
156 

Figure 52. Photo. Wildlife guard along U.S. Highway 93 on the Flathead Indian 

Reservation, MT (copyright: Marcel Huijser, WTI). 

Case Studies and Contacts 

For details on an electrified wildlife guard in Banff National Park, Canada, contact 

Terry McGuire, Parks Canada, terry.mcguire@pc.gc.ca. 

For information on wildlife guards along U.S. Highway 93 on the Flathead Indian Reservation, 

MT, contact Pat Basting, Montana Department of Transportation, (406) 523-5872, 

pbasting@mt.gov. 

Direct Benefits 

Cattle or wildlife guards offer no additional benefits in reducing WVCs compared to undisrupted 

wildlife fencing. Depending on the type of cattle or wildlife guard, the guard may be ineffective 

at discouraging certain species, or it may be only partly effective (e.g., 75–99 percent for Florida 

Key deer), depending on the type of wildlife guard.(381) Intrusions result in wildlife ending up on 

the road or in between the fences along the right of way, posing a threat to traffic safety and 

putting the animal’s life in danger. 

Indirect Benefits 

Wildlife guards are easy on drivers as they do not require them to stop or get out of their vehicle. 

In addition, in contrast to a gate, a wildlife guard cannot accidentally be left open. 
157 

Undesirable Effects 

Depending on the design, cattle or wildlife guards may be dangerous to pedestrians and cyclists 

and unpleasant to drivers. 

As mentioned above, depending on the design and target species, some cattle or wildlife guards 

may be fully or partially passable to certain wildlife species. 

Costs 

The reported cost of a specially designed wildlife guard was $30,000 (Pat Basting, Montana 

Department of Transportation, personal communication). 

Guidelines 

See Peterson and others for guidelines.(381) 

ACCESS FOR PEOPLE SUCH AS HIKERS, SKIERS, CYCLERS, AND FISHERS 

Wildlife fencing presents people with a barrier. In some cases, access has been provided that 

allows people to cross the wildlife fence, for example to hike, cycle, or fish on the other side of 

the fence. Angled openings (figure 53) and swing gates, with or without steps to accommodate 

for deep snow (figure 54), have been implemented to allow access for people. In The 

Netherlands, gates for people have been installed that have angled doors that allow gravity to 

automatically close the gate (Marcel P. Huijser, Western Transportation Institute, Montana State 

University, personal communication). 

Figure 53. Photo. Angled opening in fence allowing access for people along U.S. Highway 

93, MT (copyright: Marcel Huijser, WTI). 
158 

Figure 54. Photo. Swing gate in fence (spring loaded) allowing access for people, along the 

Trans-Canada Highway in Banff National Park, Alberta, Canada (copyright: Adam Ford, 

TCH research project/WTI-MSU). 

Case Studies and Contacts 

For details on an opening in a fence along U.S. Highway 93 (south), contact Pat Basting, 

Montana Department of Transportation, (406) 523-5872, pbasting@mt.gov. 

Direct Benefits 

No direct benefits were identified in the literature review. 

Indirect Benefits 

No indirect benefits were identified in the literature review. 

Undesirable Effects 

Some access designs (e.g., the opening in a fence along U.S. Highway 93 (south) in Montana), 

have not been evaluated yet with regard to wildlife potentially using the structure to get into the 

right of way. 

Not all access designs are accessible to handicapped individuals. 
159 

Costs 

No costs were identified in the literature review. 

Guidelines 

No guidelines were identified in the literature review. 

BOULDERS IN THE RIGHT OF WAY 

Large boulders have been placed in the right of way, outside of the clear zone, as an alternative 

to wildlife fencing. Large boulders are thought to make it hard for animals, especially ungulates, 

to walk across an area. Boulders have been used for this purpose along State Route 260 in 

Arizona (Terry Brennan, U.S. Forest Service, personal communication; Norris Dodd, Arizona 

Game and Fish Department, personal communication) (figure 55 and figure 56). The boulder 

barrier was not extended through areas with steep slopes, since it was thought that wildlife would 

not move through these steep areas. However, animals have traveled through these areas. The 

barrier is thought to be effective with exception of the gaps in the steep areas. (Norris Dodd, 

Arizona Game and Fish Department, personal communication). 

Figure 55. Photo. Large boulders pPlaced in the right of way as a barrier to elk and deer 

along State Route 260 in Arizona (copyright: Marcel Huijser). 
160 

Figure 56. Photo. Large boulders placed in the right of way as a barrier to elk and deer 

with a view of State Route 260 (under construction) in Arizona (copyright: Marcel Huijser). 

Case Studies and Contacts 

For information about the use of boulders as an alternative to wildlife fencing along State Route 

260 in Arizona, contact Terry Brennan, Tonto National Forest, (602) 225-5375, 

tbrennan@fs.fed.us; and Norris Dodd, Arizona Game and Fish Department, Pinetop, AZ 85935, 

(928) 367-5657, doddnbenda@cybertrails.com. 

Direct Benefits 

The large boulders are believed to be an effective alternative to wildlife fencing if all the gaps 

are eliminated. 

Indirect Benefits 

In contrast to wildlife fences, large boulders are natural and, depending on the landscape, can 

address the landscape aesthetics concern associated with wildlife fences. 

Undesirable Effects 

If boulders are indeed an absolute barrier to ungulates and/or other species groups, safe passage 

may have to be provided for wildlife at selected locations. See the previous section on wildlife 

fencing on addressing undesirable effects of wildlife fencing. 

Costs 

Costs for the Arizona case study were less than $197 per m (less than $60 per linear ft) 

(Norris Dodd, Arizona Game and Fish Department, personal communication). 
161 

Guidelines 

No guidelines were identified in the literature review. 

LONG TUNNELS AND LONG BRIDGES OVER LANDSCAPE 

In this section, long tunnels (or landscape bridges) are defined as tunnels that are at least several 

hundreds of meters long, sometimes many kilometers. They may include “cut and cover” 

strategies, where a “roof” is constructed over the road rather than a tunnel, leaving the landscape 

above intact. Long bridges (or elevated road sections) are defined as bridges that are at least 

several hundreds of meters long, sometimes many kilometers. Long tunnels and bridges are 

primarily constructed because of the nature of the terrain (e.g., through a mountain, across a 

floodplain), but in some cases they are constructed to avoid areas that are ecologically very 

sensitive and where no alternatives are available. If the nature of the terrain permits, animals can 

move freely over long tunnels or under long bridges, and because the animals are physically 

separated from traffic, WVCs are eliminated. While long tunnels and long bridges may be among 

the most effective mitigation measures to reduce roadkill, they are rarely specifically designed to 

reduce WVCs. 

Long tunnels and long bridges should not be confused with wildlife overpasses or wildlife 

underpasses. Wildlife overpasses and underpasses are typically combined with wildlife fencing, 

and it is the wildlife fencing that keeps the animals from entering the roadway, whereas the 

primary function of wildlife overpasses and wildlife underpasses is to mitigate the barrier effect 

of the wildlife fencing and to provide safe crossing opportunities. Long tunnels and long bridges 

are not necessarily combined with wildlife fencing. They allow for free animal movements over 

or under the road, as well as other ecosystem processes, including those related to soil and 

hydrology (figure 57). 

Figure 57. Photo. Long bridge on Arizona State Route 260 constructed in such a way as to 

minimize the impact to soil and vegetation (copyright: Marcel Huijser). 
Case Studies and Contact 

At one section of the U.S. 61 reconstruction project in Minnesota, Silver Creek Cliff, a tunnel was 

constructed. To meet the design standards for the reconstruction, the cliff top needed to be removed 

(estimated to be a million cubic yards of cut). Environmental and aesthetic concerns led to what was 

actually a less expensive solution. The Minnesota Department of Transportation was able to use the 

existing highway as a bypass during tunnel construction, which they would not have been able to do if a 

typical cut would have been used. This approach resulted in cost savings of earthwork (to remove the cliff 

top which was estimated to be one million cubic yards (765,000 cubic meters)) and no need for a 

construction of a bypass (estimated at $2 million due to the terrain restrictions). Additionally, this 

alternative was a much more environmentally friendly and aesthetically pleasing. The tunnel was 

constructed using the new Australian Tunneling Method (Scott Bradley, Minnesota Department of 

Transportation, personal communication). For further information, contact Scott Bradley, FASLA, Chief 

Landscape Architecture, MNDOT, (651) 284 3758, scott.bradley@dot.state.mn.us. 

When State Route 40 in Florida was constructed, a long bridge over dry land was built in anticipation of a 

planned canal (figure 58). The canal was never built, but the bridge allows wildlife to pass unharmed 

underneath. 

Figure 58. Photo. Long bridges do not have to be excessively large to provide ample space for wildlife 

crossings. While not exceedingly long, this bridge provides plentiful space for both the 

stream and wildlife to cross. 

There are numerous other examples of long bridges and tunnels. A cut and cover option was 

used for a long tunnel in the United Kingdom (A12 Hackney to M11 link). A long bridge was 

constructed on roadway A9, over an important wetland surrounding the Mino River near Galicia, 

Spain. Interstate 70 in Glenwood Canyon, CO, has several sections that are elevated viaducts. 

162 
163 

Direct Benefits 

No data are available, but since there is a physical separation of the vehicles and animals, WVCs 

should be reduced by 100 percent or close to 100 percent. 

Indirect Benefits 

Long tunnels and long bridges allow for connectivity at the landscape level for a wide array of 

species. In multifunctional and agricultural landscapes, they also allow for humans, forest 

products, crops and livestock to freely move from one side of the road to the other. 

Undesirable Effects 

No undesirable effects were identified in the literature review. 

Costs 

A 200-m (660-ft)-long tunnel was constructed for Can$24,000,000. A 200-m (660-ft)-long 

elevated roadway (long bridge) cost Can$12,500,000 (Anthony P. Clevenger, Western 

Transportation Institute, Montana State University, personal communication). 

Guidelines 

No guidelines were identified in the literature review. 

WILDLIFE UNDERPASSES AND OVERPASSES 

Wildlife underpasses and overpasses are not always installed in combination with wildlife 

fencing (see earlier section on wildlife fencing in this chapter).(382) In some cases, the landscape 

in the surroundings of the crossing structures may guide the animals to the crossing structures, 

reducing the need for wildlife fencing. In other cases, wildlife fencing may not be on option, for 

example because of landscape aesthetics. For a discussion on wildlife underpasses and 

overpasses see the earlier section on addressing the undesirable effects of wildlife fencing in this 

chapter. 

165 

CHAPTER 9. PLANNING AND DESIGN CONSIDERATIONS 

Many of the WVC mitigation measures discussed in this paper focus on spot or corridor 

solutions where WVCs are already a problem on existing roadways. However, integration of 

transportation planning and wildlife management on a regional level can impact WVCs. 

Typically these planning efforts are focused on mitigating environmental impacts. The contextsensitive design and context-sensitive solution (CSD/CSS) process may be a way to incorporate 

consideration of WVCs in planning and design. This section discusses selected planning efforts 

that can have an impact on reducing WVCs, including the following: 

• Identifying and prioritizing WVC problem areas. 

• Improved data collection and monitoring. 

• Adjusting the road alignment by: 

o Considering the no-build option. 

o Considering alternative alignments. 

o Road removal. 

• Consideration of design features of roadways. 

IDENTIFYING AND PRIORITIZING WVC PROBLEM AREAS 

WVC “hot spots” can be identified with crash and carcass data. To develop an understanding of 

the root causes of WVCs, one must also consider a context broader than simply the site of an 

animal carcass. This approach is multidisciplinary in nature and involves landscape ecology (a 

discipline that stresses understanding of the interactions of physical and biological phenomena at 

multiple spatial and temporal scales) and conservation biology (a discipline that integrates 

biological, social and physical sciences to develop a sound basis for the conservation, 

management, and restoration of biological resources). These scientific fields of study can lend 

understanding to the effects of spatial patterns, ecological processes, animal behavior, and 

related factors. Design of transportation systems and ecological networks (habitat linkage zones 

or greenways) should be based on such concepts. In turn, this scientific knowledge can be used 

in coordinated planning at multiple scales (e.g., site, local and regional planning) to address 

WVCs in broader contexts, thus avoiding such conflicts whenever possible. 

In order to focus limited resources, some states have identified and prioritized habitat linkage 

zones that act as corridors for animals to move between major areas of habitat (e.g., development 

of Wildlife Habitat Linkage Plans). Again, the primary motivation is to improve habitat 

connectivity for wildlife and not necessarily to reduce WVCs. However, with proper planning 

these habitat corridors can focus animal movement to specific locations along the highway, 

which in turn allows for more focused mitigation of WVCs at those crossing locations. 

There are a number of methods for prioritizing habitat linkage zones. One method is to look at 

existing WVC data to identify hot spots. Although this is a primary input for many prioritization 

methods, by itself it is not very forward looking, because changes in land use patterns can cause 

changes in animal movements. Also, there are many other sources of information that can be 
166 

used to identify potential future WVC problem areas, such as known locations of threatened and 

endangered species and known migration corridors. 

Ruediger has been involved in a number of regional and statewide wildlife habitat linkage 

plans.(383) In formulating such plans, he suggests using a variety of data including aerial photos, 

vegetation maps, topography maps, wildlife habitat and range maps, and roadkill information. 

Another important source of information is local knowledge, which can be accessed by holding a 

workshop with appropriate stakeholders. The aforementioned data should be collected and 

presented on maps for this workshop. Also, a method for selecting prioritized linkage zones 

should be determined prior to the meeting. It is important to record information about the linkage 

zones identified (e.g., location, species of concern, local agencies and individuals with special 

knowledge of the linkage zone, major purpose of the linkage zone, and a prioritization ranking 

for the linkage zone). 

According to Levy, a prioritized linkage zone map was created for Arizona.(384) The map was 

created during Arizona’s Missing Linkages Workshop in April 2004. The workshop included 

representatives from ADOT, FHWA, U.S. Fish and Wildlife Service, Arizona Game and Fish 

Department, U.S. Department of the Interior’s Bureau of Land Management, Tonto National 

Forest, and Northern Arizona University. This initial map was refined during six ecoregional 

workshops in November 2004. Geographic Information Systems (GIS) databases were helpful in 

obtaining some of the data that were used in prioritizing the linkage zones. 

The University of Alaska Anchorage produced a “toolbox” for the Alaska Department of 

Transportation and Public Facilities to assess how Alaskan roads affect habitat quality and 

connectivity.(385) The project specifically addressed the use of GIS to assist transportation 

planners with project development. Based on workshops, GIS data sets, and relevant literature, 

the effort identified high-priority areas for habitat linkage based on four criteria: 

• Places where good data exist on habitat features and that represent the diversity of 

ecosystems. 

• Riparian corridors. 

• Places where funding can be leveraged. 

• Places that can provide a source of baseline data. 

The Florida Department of Transportation has created a program to identify and prioritize habitat 

linkage zones that intersect with highways.(386) The purpose of this program is to consider 

underpasses or culverts on a statewide level in order to restore habitat connectivity and 

ecological processes. This method uses a rule-based GIS model to assimilate multiple factors 

such as roadkill hot spots, riparian areas, greenways, protected conservation lands, and known 

wildlife movement routes. 

The Idaho Transportation Department identified wildlife connectivity areas using an approach 

that integrated GIS spatial data, GIS linkage model analysis, and expert workshops to identify 

areas of interest for mitigation consideration in the southeast corner of the state.(387) A number of 
167 

models predict optimal crossing locations for specific species such as Key deer in Big Pine Key, 

FL, and grizzly bear in the area around Evaro Hill, MT.(388,389) 

Once habitat linkage zones are identified and prioritized, efforts need to be made to preserve 

them. A crossing structure can be constructed in a high WVC zone only to have development 

adjacent to the highway block animal movement so the animals cross at another location along 

the highway. 

This type of effort is inherently multi-agency in nature and should involve local land grants, 

cities, counties, special interest groups, land owners, resource agencies, rail lines, and State 

DOTs. A team is attempting to follow this process for Interstate 90 on Bozeman Pass in 

Montana. The team includes Gallatin Valley Land Trust, Forest Service, Montana Department of 

Transportation, Montana Rail Link, American Wildlands, and others. This location is clearly a 

habitat corridor as two areas of the Gallatin National Forest are separated by a corridor that 

includes private land under heavy development, an interstate, and a rail line. Any effort to 

preserve the corridor by a single agency would be ineffective, because increased interstate traffic 

and increased development each threaten to block animal movement. However, by prioritizing 

specific crossing locations, land trusts can focus efforts to preserve adjacent lands, and the 

Montana Department of Transportation can optimize its investment in mitigation measures on 

the interstate. 

The effort must go beyond prioritizing greenways to incorporation of linkage zones into 

transportation and conservation planning elements (of comprehensive plans) that are developed 

at both local and state levels of government. At a minimum, the statewide transportation 

improvement program should be reviewed annually for reconstruction projects that cross these 

habitat linkage zones. Incorporating WVC mitigations into a reconstruction project (especially at 

the initial project planning stage) will be much less expensive than installing them as separate 

projects. 

Case Studies and Contacts 

For information on efforts in Arizona, contact Steve Thomas, Environmental Program Manager, 

FHWA Arizona Division, steve.thomas@fhwa.dot.gov. 

For information on Florida’s prioritization efforts, contact Dan Smith, Western Transportation 

Institute, (406) 994-6114, dan.smith@coe.montana.edu. 

For general methodologies for prioritizing habitat linkage zones, contact Bill Ruediger, Wildlife 

Consulting Resources, (contracted by USDA Forest Service, Wildlife, Fish and Watershed Unit, 

Washington Office) bruediger@fs.fed.us. 

For information on the Bozeman Pass collaboration in Montana, contact Deborah Wambach, 

Montana Department of Transportation, (406) 444-0461, dwambach@mt.gov; or Josh Burnim, 

American Wildlands, (406) 586-8175, jburnim@wildlands.org. 

For general information on the planning process, consult chapter 6 in National Research Council, 

chapter 3 in NCHRP Synthesis 305 by Evink, chapters 6 and 7 in Moore and Thorsnes, and the 
168 

following Web sites: FHWA, www.fhwa.dot.gov/planning/, and American Planning 

Association, www.planning.org.

(86,302,390) 

DATA COLLECTION AND MONITORING 

Like prioritizing habitat linkage zones (discussed in the previous section), data collection and 

monitoring will not have direct benefits in reductions of WVCs, but without good data on the 

magnitude, location, and type of WVCs, all other mitigations discussed in this report cannot be 

installed at the locations where they will have the most impact. WVC data are crucial in 

justifying and prioritizing locations for mitigation. Additionally, in order to utilize the most 

effective mitigations for WVCs, the effectiveness of currently installed measures must be 

evaluated. 

As discussed in the chapter on Causes and Factors, there are three primary sources of WVC data: 

insurance data (which are not spatially located), crash reports, and animal carcass counts. The 

NCHRP Project 20-05–Topic 37-12 provides a current state of the practice on WVC data 

collection. The report for this project is currently in draft form.(31) A survey conducted as part of 

this report asked states if they collected WVC data (crashes or carcasses). Of the 30 State 

transportation departments that responded to the survey, 19 collected crash data on WVCs, 

13 collected carcass data, and 8 collected neither. It should be noted that although the states 

reported that they did not collect WVC data, a review of crash reports shows that every state 

except one has “animal” as a check box on the crash form. Of the 30 responding state 

departments of natural resources, 9 said they collected crash data, 15 said they collected carcass 

data, and 12 said they collected neither. There is also a dramatic drop in data collection on local 

and collector roads compared to interstates and arterials. Many states discussed problems with 

the data, including inconsistencies, location accuracy, and underreporting. 

There are currently efforts underway to improve WVC data. For collecting carcass data, the 

Maryland Department of Transportation has a program Large Animal Accident Removal 

Reporting System (LARRS) that is implemented from the top down so that there is a consistent 

standard within the department. This program is integrated with an existing form for 

maintenance tasks that maintenance workers are required to fill out regardless of carcass data 

collection. Since maintenance workers are required to fill out the form anyway, they are more 

likely to accurately complete the required form (as opposed to adding another form exclusively 

for carcass data). To assist with data collection of carcasses, GPS-enabled handheld computers 

(personal digital assistants) have been developed, mostly as prototypes. One such system is the 

Roadkill Observation Collection System (ROCS) currently under development by the Western 

Transportation Institute. Another potential source of data is the use of volunteers. 

Case Studies and Contacts 

For information on the Maryland LARRS carcass data collection method, contact William 

Branch, Maryland Department of Transportation, (410) 545-8626, WBranch@sha.state.md.us. 

For more information on handheld GPS units for automatically collecting data (ROCS), contact 

Amanda Hardy, Western Transportation Institute, (406) 994-2322, ahardy@coe.montana.edu. 
169 

ALTERNATIVE ALIGNMENT, ROAD REMOVAL, OR NO NEW ROAD 

Integration of transportation and conservation planning at multiple scales is essential to 

addressing WVCs. With this integration, the transportation network can be developed with 

consideration of ecologically sensitive areas, and some efforts can be made to minimize 

environmental impacts in locating new roads and possibly closing existing roads. Typically these 

efforts are aimed at conservation but can have an impact on reducing WVCs. 

There are several models that are used to assess the ecological impact of new roadway alignment 

options on wildlife. Maurer developed one such model for the Pennsylvania Department of 

Transportation.(391) A community-based, landscape-level terrestrial decision support system was 

developed with the objective to maintain the ecological integrity of Pennsylvania ecosystems. 

This model is founded on seven basic characteristics: comparison, reasonableness, practicality, 

sensitivity, data, process, and decision making. Variables for Assessing Reasonable Mitigation in 

New Transportation (VARMINT) include habitat importance, stewardship, patch size and shape, 

connectivity, proximal land use, relative significance, natural processes, diversity, anthropic use, 

and intangibles. Each site is assigned scores for each of these criteria. Comparison of scores 

determines relative ranking. 

CSD/CSS processes are used to incorporate community values, aesthetics, and environmental 

and other priorities into the design process. Using the CSD/CSS process could result in 

alignments that minimize the impact of WVCs. For more information on the overall CSD/CSS 

process, refer to the following reports: 

• NCHRP 480, A Guide to Best Practices for Achieving Context Sensitive Solutions.(392)

• AASHTO Guide for Achieving Flexibility in Highway Design.(393)

• NCHRP Report 69, Performance Measures for Context Sensitive Solutions: A Guidebook 

for State DOTs.(394) Note that this report details how to develop a CSD/CSS program and 

track performance with surveys. Although there is some discussion on developing 

performance criteria (at the project and programmatic level), specific measures are not 

discussed as the title may imply. 

In 2003, the California Department of Transportation closed a functional but little-used highway 

interchange (e.g., on ramps, off ramps and underpass) on State Route 91 called the Coal Canyon 

Interchange. The mainline is eight lanes with 200,000 vehicles per day, but the interchange was 

used by fewer than 150 motorists per day. The main motivation for the closure was connecting 

habitat between Chino Hills and Cleveland National Forest. However, WVCs were another 

consideration due to mountain lion roadkills.(395) The underpass (in combination with fencing) 

now serves as a critical connection in a wildlife migration route.(395)

Closing the Coal Canyon Interchange was seen by one city as a loss of tax revenue since it 

limited development on one side of the highway. There will likely be heavy opposition to such 

closures by some landowners based on concerns regarding reduced property values and ability to 

develop property. Obviously, significant resources went into the original construction and 

maintenance of the roadway and removing a roadway essentially wastes that initial investment in 
170 

infrastructure. A better option is to more strategically plan the transportation network (e.g., do 

not build the road in the first place). However, in some cases it may be feasible to remove a 

roadway given the right mix of limited development, public grass roots support, and preservation 

of surrounding habitat. 

The Coal Canyon project cost $440,000 to remove the roadway underpass, remove the on/off 

ramps, provide a median turnaround for emergency vehicles, and provide fencing to guide 

animals to the underpass. Note that $40,000,000 was used to purchase the surrounding land to 

protect the habitat. 

Most other examples of removing roadways in the United States involve gravel roads on public 

lands (e.g., forest service roads). As Switalski and others point out, the impact to wildlife has not 

been monitored or researched.(396) Switalski and others suggest costs for road removal are as 

follows: 

• Gating the roadway ends and leaving the road intact: $1,000–2,800. 

• Blocking the roadway ends with permanent traffic barriers such as boulders and berms: 

$800–1,000. 

• Ripping roadbed: $400–1,200 per km ($650–1,950 per mi). 

• Stream crossing restoration: $500–150,000 per crossing. 

• Full recontour of slopes: $3,000–200,000 per km ($4,850–322,000 per mi).(396)

Figure 59 shows a road removal in process in Belgium. In this case there was an alternate route, 

and this roadway was considered unneeded. It was replaced by a nonmotorized multiuse 

pathway. 
171 

Figure 59. Photo. Road removal in progress in Belgium (note that a path for pedestrians 

and bicyclists remains in place.) (copyright: Bethanie Walder). 

Case Studies and Contacts 

For further information on the Coal Canyon Interchange removal, contact California Department 

of Transportation, District 12, (949) 724-2000. 

Although primarily focused on roads on public lands, a good source of information on road 

removal is the Wildlands Center for Preventing Roads, http://www.wildlandscpr.org/ (accessed 

January 25, 2007). 

CONSIDERATION OF DESIGN FEATURES 

Consideration of some basic WVC mitigation principles in designing various elements of a 

highway could minimize the potential for WVCs. Some of these items have been discussed in the 

previous chapters but could be implemented as part of the initial design and thus are mentioned 

here. The following items should be considered when designing roadways that have a high 

likelihood for WVCs (see chapter 2), such as two-lane, rural/suburban, low-/medium-volume 

highways that pass through wildlife habitat: 

• Steep side slopes can hide approaching animals from the driver’s view. The AASHTO 

Green Book recommends slopes of one foot vertical to four feet horizontal or flatter.(1) It 

further recommends that slope transitions should be gently rounded. This slope is clearly 

visible (whether cut or fill) by the driver. Designers should use steeper fill slopes with 

caution, as drivers may not be able to see deer approaching the roadway until the animal 
172 

leaps over the guardrail. If a steeper side slope is used, consider a landing on the top for 

animals to be visible to drivers (and visa versa) before jumping over the guardrail. 

• At locations where the roadway crosses drainages, known migration corridors, or known 

animal habitat, the designer should take extra caution to make animals visible to drivers. 

At these locations avoid curves, steep side slopes, and narrow clear zones. 

• At locations where culverts or bridges are installed, consider making the culverts and 

bridges wide enough to include opportunities for animals to cross under the road. This 

consideration relates especially to terrestrial animals that may require a bank on either 

side of a stream or river to cross under the road. 

• When designing drainage, consider the impact on wildlife movement and attraction. 

Avoid creating pooled water in the right of way which can create attractive vegetation. 

Some wildlife will avoid crossing rip-rap. If rip-rap funnels animals to an undesirable 

crossing location, consider filling gaps in the rip-rap with sand and gravel (which may 

make it more conducive for animals to cross) or extend the rip-rap to a more suitable 

crossing location. 

• When considering seeding mixes for the roadside, consider unpalatable species. Also 

consider plants that do not grow so tall as to visually obscure animals approaching the 

roadway. 

• Concrete median barriers can cause problems for wildlife. When crossing the roadway, 

wildlife may pause at the barrier or turn around, increasing their time in the roadway. A 

summary of the literature by Clevenger and Kociolek found that “the general hypothesis 

is that concrete Jersey barriers may increase the risk of direct vehicle mortality [of 

wildlife].”(310) Mitigations include gaps in the barrier at strategic hot spot locations, 

cutouts at the bottom for small animals, or using cable barrier designs instead. 

• Aside from the basic principles listed here, the designer should estimate the potential 

magnitude of the WVC problem when designing a road. If there are areas along the route 

that have a high potential for WVCs, the designer should consider including some of the 

mitigations mentioned in this report (e.g., wildlife fencing). 
173 

 CHAPTER 10. EVALUATION OF MITIGATION METHODS BY TECHNICAL 

WORKING GROUP 

The WTI-Berger Team convened a Technical Working Group Meeting on January 25, 2007, at 

FHWA Headquarters. The Technical Working Group consisted of a panel of seven national 

experts in the area of WVCs. The experts were identified and selected by the FHWA Project 

Committee during the June 30, 2006, kickoff meeting. An effort was made to include 

representation from academia, State transportation departments, Federal agencies, and 

nongovernment organizations. The Technical Working Group members are listed in table 9. 

Table 9. Technical working group members. 

Name Organization 

Bill Branch Maryland DOT 

Michael Pawlovich* Iowa DOT 

Scott Jackson U.S. Fish and Wildlife Service 

Susan Hagood The Humane Society of the United States 

Brent Haglund Sand County Foundation 

Sandy Jacobson Forest Service 

Keith Knapp Texas Transportation Institute 

*Participated by phone 

The Technical Working Group reviewed a draft version of this report and helped identify other 

sources of information that would be beneficial. Another purpose of this meeting was to have a 

group of national experts evaluate the effectiveness of the mitigations based on their knowledge. 

Initially, the Project Committee (FHWA) and the WTI-Berger Team wanted to use the NCHRP 

500 categories for safety mitigations. The categories defined in the NCHRP 500 report are: 

Tried (T)—Those strategies that have been implemented in a number of locations 

and may even be accepted as standards or standard approaches but for which valid 

evaluations have not been found. These strategies, while in frequent or even 

general use, should be applied with caution, carefully considering the attributes 

cited in the guide and relating them to the specific conditions for which they are 

being considered. Implementation can proceed with some degree of assurance that 

there is not likely to be a negative impact on safety and very likely to be a positive 

one. As the experiences of implementation of these strategies continues under the 

AASHTO Strategic Highway Safety Plan initiative, appropriate evaluations will 

be conducted, so that effective information can be accumulated to provide better 

estimating power for the user, and the strategy can be upgraded to a “proven” 

one.(397)

Experimental (E)—Those strategies that have been suggested and that at least one 

agency has considered sufficiently promising to try on a small scale in at least one 

location. These strategies should be considered only after the others have proven 

not to be appropriate or feasible. Even where considered, their implementation 

should initially occur using a very controlled and limited pilot study that includes 
174 

a properly designed evaluation component. Only after careful testing and 

evaluations show the strategy to be effective should broader implementation be 

considered. As the experiences of such pilot tests are accumulated from various 

state and local agencies, the aggregate experience can be used to further detail the 

attributes of this type of strategy so that it can be upgraded to a “proven” one.(397)

Proven (P)—Those strategies that have been used in one or more locations and for 

which properly designed evaluations have been conducted that show it to be 

effective. These strategies may be employed with a good degree of confidence, 

but with the understanding that any application can lead to results that vary 

significantly from those found in previous evaluations. The attributes of the 

strategies that are provided will help the user judge which strategy is the most 

appropriate for the particular situation.(397)

A properly designed evaluation for the “proven” category has a fairly strict definition in the 

safety field, including a Bayesian analysis of crash data. (Note: Bayesian analysis evaluates the 

consistency or inconsistency of new evidence with a given hypothesis.) Bayesian analysis does 

require the a priori assignment of probabilities to hypotheses, which, depending on the question, 

may be subjective. As an example, a mitigation that has been proven to keep animals off the road 

would not be proven if no studies on WVCs with a Bayesian analysis were completed, even 

though logically these would be known to be effective. The Technical Working Group concluded 

that under this definition, none of the mitigations would be defined as proven, and almost all of 

the mitigation measures would be classified in the “tried” category. The Working Group 

members felt that the strict safety definitions would not do justice to their experience with certain 

mitigation measures and effectiveness data gathered on them. The meaning of “properly 

designed evaluation” was left up to the individual members of the Technical Working Group and 

did not require a Bayesian analysis of crash data. To avoid confusion with the safety definitions, 

the names of the above three definitions were changed. Also, two categories were added. The 

new definitions adopted by the Technical Working Group for this evaluation were: 

• Successful (similar to “proven” safety definition): Mitigation measures that have been 

used in one or more locations and for which properly designed evaluations have been 

conducted that show them to be effective. 

• Demonstrated (similar to “tried” safety definition): Mitigation measures that have been 

implemented in multiple locations and that may even be accepted as standards or 

standard approaches but for which valid evaluations have not been found. 

• Attempted (similar to “experimental” safety definition): Mitigation measures that have 

been suggested and that at least one agency has considered sufficiently promising to try 

on a small scale in at least one location. However, data on effectiveness have not been 

documented or have not yet been published. 

• Unknown: Mitigation measures that have not been tried or that have been tried, but not 

for WVC reduction, were not implemented correctly, or are only recently being tried. 
175 

• Failed: Mitigation measures that have been used in one or more locations and for which 

properly designed evaluations have been conducted and show them NOT to be effective. 

The procedure for voting was as follows. The mitigation was described by the WTI-Berger 

Team. The panel members were asked to base their vote on the effectiveness in reducing DVCs. 

The vote was not based on mitigation for other effects related to roads and traffic (e.g., barrier 

effect) or for species other than deer (white-tailed and mule deer combined). Deer are involved 

with the majority of all reported WVCs (chapter 2). If panel members had been asked to consider 

multiple species representing very different species groups, the procedure would have had to 

have been repeated for each species or species group. Limited data are available to evaluate the 

effectiveness of many of the mitigation measures for species other than deer. 

After hearing a description of each individual mitigation measure, the Technical Working Group 

voted. If the vote was unanimous, the next mitigation was considered. If there was contention, 

the panel discussed the rationale for their votes, and the members were allowed to change their 

votes based on new information provided by the other panel members. However, a unanimous 

vote or consensus was not required. 

The results of this process are shown in table 10. The mitigation “reduce speed by posting 

advisory speed signs” was not included since the Group felt this was very similar to warning 

signs. The mitigation “carcass removal” was also not included since the Group felt that this 

mitigated for scavengers only and not for deer. The mitigation “increase visibility of animals to 

drivers: reduce height of snow banks” was not included because this section was added to the 

report after the ranking meeting. Most of the mitigations that provide crossing opportunities are 

not included, since their purpose is to mitigate the barrier effect of fencing and are not 

mitigations for WVCs by themselves. 
176 

Table 10. Technical working group rankings. 

 Votes Received 

Measure 

Successful Demonstrated Attemp

-ted 

Unknown Failed 

Mitigations that attempt to influence driver behavior 

Public information and education 7 

Standard wildlife warning signs 2 5 

Large, nonstandard wildlife warning signs 1 5 1 

Seasonal wildlife warning signs 7 

Roadside animal detection systems (RADS) 2 5 

In-vehicle (veh.) warnings: RADS to on-board 7 

In-veh. warning: on-board animal detectors 7 

Increase visibility: roadway lighting 7 

Increase visibility: vegetation removal 7 

Increase visibility: wider road striping 7 

Reflective collars (buffalo) 7 

Reduce traffic volume on road network 7 

Seasonal closure 7 

Reduce speed by reducing posted speed limit 6 1 

Reduce speed by traffic calming 1 5 1 

Wildlife crossing guards 4* 3 

Mitigations that attempt to influence animal behavior or population size 

Deer reflectors and mirrors 6 1 

Audio signals in row or deer whistles 1 6 

Olfactory repellants 3 4 

Deer flagging models 6 1** 

Hazing 3 4 

Investigate deicing alternatives 7 

Intercept feeding 7 

Influence species/nutritional value in ROW 7 

Expanded median 7 

Mitigations that seek to reduce wildlife population size 

Wildlife culling 7 

Wildlife relocation 6 1 

Anti-fertility treatment 7 

Habitat alteration 4 3 

Mitigations that attempt to physically separate animals from the roadway 

Wildlife fencing 4 3 

Boulders fence 7 

Long tunnels and long bridges 7* 

Underpasses and overpasses 7 

Underpasses/overpasses and fencing 7 

*Although this mitigation has not been proven through evaluation procedures, it is intuitive that it definitely works. 

**Although this technique has been tried, it was not implemented appropriately. 

Note: ROW = right of way.
177 

Although the above table gives good insight into what works and what does not, most of the 

mitigations fall into the uncertain categories (demonstrated, attempted, or unknown). Also, it 

does not take into account costs of implementation, feasibility of implementation, and overall 

effectiveness. As a follow-up, the Technical Working Group was asked (by email) to categorize 

the same mitigation measures as the following: 

• Recommended for implementation. 

• Recommended for further research. 

• Not recommended for implementation or further research. 

The results of this categorization are presented in table 11. Note that, relative to this second 

categorization effort, there are some mitigations where one or more members of the group did 

not vote. 
178 

Table 11. Technical working group recommendations. 

 Votes Received 

Measure Recommended 

Further 

Research 

Not 

Recommended

Mitigations that attempt to influence driver behavior 

Public information and education 7 

Standard wildlife warning signs 2 

Large, nonstandard wildlife warning signs 1 5 

Seasonal wildlife warning signs 7 

Roadside animal detection systems (RADS) 2 5 

In-vehicle (veh.) warnings: RADS to on-board 

In-veh. warning: on-board animal detectors 7 

Increase visibility: roadway lighting 7 

Increase visibility: vegetation removal 7 

Increase visibility: wider road striping 

Reflective collars (buffalo) 

Reduce traffic volume on road network 

Seasonal closure 

Reduce speed by reducing posted speed limit 6 1 

Reduce speed by traffic calming 1 5 1 

Wildlife crossing guards 4 3 

Mitigations that attempt to influence animal behavior or population size 

Deer reflectors and mirrors 1 5 

Audio signals in row or deer whistles 1 6 

Olfactory repellants 3 4 

Deer flagging models 1 6 

Hazing 2 5 

Investigate deicing alternatives 1 4 2 

Intercept feeding 2 5 

Influence species/nutritional value in ROW 5 1 

Expanded median 4 2 

Mitigations that seek to reduce wildlife population size 

Wildlife culling 2 4 1 

Wildlife relocation 1 6 

Anti-fertility treatment 3 4 

Habitat alteration 1 3 3 

Mitigations that attempt to physically separate animals from the roadway 

Wildlife fencing 6 1 

Boulders fence 2 5 

Long tunnels and long bridges 2 4 1 

Underpasses and overpasses 2 4 1 

Underpasses/overpasses and fencing 4 1 

Note: ROW = right of way. 

Referring to table 11, the panel voted on whether each mitigation measure should or should not 

be implemented or whether further research should be undertaken. A majority of votes (four or 
179 

more) was required to make a positive recommendation for implementation of the mitigation 

measure. Also, a majority of votes (four or more) for “not recommended” resulted in the 

rejection of the mitigation measure. Finally, if a majority did not cast votes to recommend 

implementation, but at least four votes were divided between “recommended” and “further 

research,” the panel’s recommendation was that further research should be undertaken for that 

particular mitigation measure. 

When interpreting the results, it is important to keep in mind that these opinions only relate to 

deer and to mitigating DVCs. The opinions do not necessarily relate to other species or 

mitigating other effects associated with roads and traffic such as habitat loss, reduced habitat 

quality, and barrier effect (except for direct road mortality). The subsequent outcome of this 

process is as follows: 

• Where feasible and appropriate, the following mitigations should be implemented: 

o Public information and education. 

o Wildlife fencing. 

o Underpasses and overpasses with fencing. 

• Research or construction resources should not be used for the following mitigations: 

o Standard wildlife warning signs. 

o Deer reflectors and mirrors. 

o Audio signals in the right of way or deer whistles on vehicles. 

o Olfactory repellents. 

o Deer flagging models. 

o Hazing. 

o Intercept feeding. 

o Wildlife relocation in order to reduce population size. 

o Anti-fertility treatment in order to reduce population size. 

o Seasonal road closures. 

o Reflective collars placed on wildlife. 
180 

• Mitigations that may be promising, but require further investigation include the 

following: 

o Reduce traffic volume on road network. 

o Reduce speed by reducing the posted speed limit. 

o Reduce speed by traffic calming or reducing the design speed. 

o Wildlife crossing guards. 

o Large, nonstandard wildlife warning signs. 

o Seasonal wildlife warning signs. 

o Animal detection systems. 

o In-vehicle warnings: roadside animal detection system communicating with onboard computers. 

o In-vehicle warnings: on-board animal detectors. 

o Increase visibility through roadway lighting. 

o Increase visibility through vegetation removal. 

o Investigate deicing alternatives. 

o Influence plant species in the roadside to limit nutritional value. 

o Reduce population size through wildlife culling. 

o Reduce population size through habitat alteration. 

o Boulders forming a barrier. 

o Long tunnels and long bridges. 

o Overpasses and underpasses by themselves. 

o Wider more reflective striping along white line. 

o Expanded median. 
181 

CHAPTER 11. GAPS IN CURRENT KNOWLEDGE 

This chapter summarizes the challenges that currently prevent a systematic, nationwide approach 

to WVC reduction. 

DATA ISSUES 

Generally, the greatest challenge to reducing WVCs is the absence of reliable information and 

documentation on mitigation measures such as effectiveness, historic use, challenges, etc. This 

lack of data is characterized by the fact that the Technical Working Group (chapter 10), 

categorized 20 of the 34 mitigations as “recommended for further research.” There are numerous 

syntheses (including this one) that summarize potential solutions to WVCs. However, the 

effectiveness of a number of mitigation measures is still uncertain due to lack of evaluation, 

inaccurate data collection, and inconsistent measures of effectiveness. 

One of the challenges relating to monitoring the effectiveness of WVC mitigations is the lack of 

reliable standardized and spatially precise data on the location of WVCs and animal carcasses. 

The national databases, summarized in chapter 2, all have some shortcomings in these regards. 

Most importantly, location data are not included in the national databases (i.e., GES, FARS, and 

State Farm Insurance Claims). Most of these datasets suffer from underreporting. Inconsistently 

collected data make it difficult to accurately characterize WVC issues and properly address them 

(e.g., identifying the best location to deploy a mitigation measure to address a particular 

situation). Problems also arise when attempts are made to use such data to evaluate the 

effectiveness of various mitigation measures after they have been installed. Furthermore, data 

that have been collected are not always readily available or even analyzed. All of these issues 

pose major challenges for the current study of WVCs. 

ANALYSIS ISSUES 

Effectiveness of mitigation measures can be evaluated relative to many different criteria. Each 

criterion has its own associated characteristics and methods of measurement, which can make 

evaluation of mitigation measures based on multiple criteria a difficult task. For example, 

effectiveness can relate to collision reduction (the criteria used in this study) but also to habitat 

connectivity. These are very different parameters, namely, safety and nature conservation, that 

are measured in very different ways. Development of sound methodologies to both singly and 

collectively consider these various criteria in evaluating mitigation measures would be useful. 

Relative specifically to safety issues, some crash models exclude WVCs altogether. If AVCs are 

included in crash models, they tend to focus on road, traffic, and right of way characteristics 

only, and ecological parameters that extend away from the road are rarely included. Only a 

limited number of studies have looked at both groups of parameters at the same time. 

Relative to specific WVC problem locations, the tendency is to identify such locations using past 

roadkill data. Given the investment and life span of some of the mitigation measures, it is 

advisable, however, to project 50–80 years into the future. The potential presence, population 

viability, and needs of selected wildlife species will likely change in this time period. 
182 

NEEDED TOOLS 

With respect to specific mitigation technology used, basic research needs to be conducted to 

understand how existing mitigation measures can be made more effective. There should be a 

continuous drive to make these measures cheaper, smaller, more robust, and as mobile as 

possible to address costs, landscape aesthetics, safety concerns, operation and maintenance 

efforts, and a highly dynamic environment. 

Modeling should be further developed and applied to assist in the optimization of the location, 

type, and dimensions of mitigation measures. Basic data collection is required to obtain inputs 

for these models. Existing long-term monitoring studies may need to be supplemented with 

studies that address specific questions that may not have been addressed yet. Once the 

recommendations based on these models have been implemented, the mitigation measures 

should be monitored for their effect on population viability parameters to verify that the models 

simulate the real world environment to an acceptable degree. 

Addressing the broader picture, tools and procedures should be developed to measure the effects 

of roads and traffic on ecosystem processes, how these effects can be minimized, and how the 

disrupted processes can be restored. 

SUMMARY 

To summarize, future research should focus on the following: 

• Developing and implementing guidelines and standards for collecting and reporting 

WVCs. 

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

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

further research. 

• Conducting research and development to improve existing mitigation measures. 

• Developing and applying population viability models that assist with the location, type, 

and dimensions of mitigation measures. 
183 

CHAPTER 12. COST-BENEFIT ANALYSES OF DEER COLLISION REDUCTION 

MEASURES 

This chapter summarizes the costs of the mitigation measures reviewed in this report and their 

effectiveness in reducing WVCs, specifically DVCs. The information in this chapter should be 

considered inclusively with the reviews on over 34 mitigation measures from information 

available in the literature (chapters 5–8) and the rankings of these measures by the Technical 

Working Group (chapter 10). 

The costs are presented (where possible) as cost per kilometer of road length per year. These 

costs were calculated from the various estimates found in the literature for the cost of each 

mitigation measure, as reported in the earlier chapters of this report. The potential benefits as a 

result of reducing DVCs will vary greatly depending on the measure, animal population density, 

type of roadway, and effectiveness of the measure. For this analysis, researchers used a 

hypothetical 1 km (0.62 mi) road section of a four-lane road (two lanes in each direction) that 

had five DVCs per year (see table 12). The benefits of mitigation were simply calculated as the 

avoided costs associated with the collisions prevented as a result of the mitigation measure. For 

this analysis, the cost associated with one DVC was estimated at $8,388 (see chapter 3). The 

avoided cost with the mitigation in place was then calculated by multiplying the cost of the 

collisions (five collisions times $8,388 per collision equals $41,940) times the effectiveness of 

the mitigation (expressed in terms of percent reduction in DVC). Effectiveness was estimated 

from information presented in the literature. Finally, the annual balance (dollar amount saved per 

kilometer per year) was calculated as benefit minus cost. It is important to note that the costs for 

these mitigation measures are primarily the responsibility of transportation agencies, while the 

benefits are mostly for insurance companies. Thus a positive balance between benefits and costs 

for a given mitigation measure generally indicates that the mitigation measure concerned could 

be a wise investment for society as a whole, but the costs and benefits are paid for and received 

by different groups in society. 

It should be noted that the costs and benefits in table 12 are based on the literature reviewed. The 

costs do not necessarily include all costs, such as maintenance, financing, and impact of 

construction on traffic. Benefits, as discussed in chapter 11, are measured inconsistently in the 

literature. Costs and benefits can vary widely for different sites and situations (e.g., geographic 

locations, effectiveness, frequency of WVCs, surrounding terrain). For these reasons, the dollar 

values presented in this chapter should be viewed as indicative rather than precise estimates. 

For some mitigation measures, the costs could not be translated to costs per kilometer per year, 

and no cost-benefit calculations were conducted. However, this does not necessarily mean that 

these mitigation measures are not effective in reducing DVCs or that they are not a wise 

investment. Instead it may only indicate that further research or analysis would be necessary to 

quantify their costs and benefits. 

The calculations presented here do not include inflation indexes, and discounting was not 

applied. Table 12 provides the best guess about costs, effectiveness, and benefits based on the 

information currently available. Nonetheless, the calculations only provide an initial insight into 

the balance between the costs and benefits of different mitigation measures and how the balance 
184 

compares between measures. Note that measures for which no cost estimates and no 

effectiveness estimates were available were excluded from table 12. 

The remainder of this chapter discusses the values in table 12 for each mitigation measure for 

which sufficient data were available to conduct analysis. 

Table 12. Summary cost-benefit of mitigation measures for five DVCs per km per yr. 

Mitigation measure 

Cost 

($/km/yr) 

% DVC 

Reduction 

Benefit 

($/km/yr) 

Balance 

($/km/yr) 

Standard warning signs $18 0% $0 -$18 

Enhanced wildlife warning signs $249 ? ? ? 

Seasonal wildlife warning signs $27 26% $10,904 $10,878 

Animal detection systems (ADS) $31,300 82% $34,391 $3,091 

ADS linked to on-board computer ?* 82% $34,391 ? 

On-board animal detectors $2,225* ? ? ? 

Vegetation removal $500 38% $15,937 $15,437 

Deer reflectors and mirrors $495 0% $0 -$495 

Deer whistles $23.5* 0% $0 ? 

Carcass removal $250* ? ? ? 

Population culling $2,508 50% $20,970 $18,462 

Relocation $10,260 50% $20,970 $10,710 

Anti-fertility treatment $61,702 50% $20,970 -$40,732 

Fence (including dig barrier) $3,760 87% $36,488 $32,728 

Boulders in right of way $2,461 ? ? ? 

Long bridges $781,250 100% $41,940 -$739,310 

Long tunnels or long bridges $1,500,000 100% $41,940 -$1,458,060

Fence with gap and warning signs $3,772 0% $0 -$3,772 

Fence with gap and crosswalk $5,585 40% $16,776 $11,191 

Fence with gap and ADS $9,930 82% $34,391 $24,461 

Fence with underpasses $5,860 87% $36,488 $30,628 

Fence with overpasses $26,485 87% $36,488 $10,003 

Fence with under- and overpasses $7,510 87% $36,488 $28,978 

Assumes 1 km with 5 DVCs per year. 

* Costs not in dollars/km/year, but in a different unit; see text. 

? = Unknown or uncertain. 

The costs and the potential reductions in WVCs resulting from a reduction in traffic volume, 

reduction of traffic speed, and the efforts of wildlife crossing assistants are unknown. Therefore 

these mitigation measures were not included in the analyses. 

Standard wildlife warning signs are relatively inexpensive: $62 for a 76 by 76 cm (30 by 

30 inches) sign.(195) The costs per kilometer per year (two signs per km, one sign for each travel 

direction, assumed life span of 7 years, no maintenance) are $18, but since standard wildlife 

warning signs are considered ineffective in reducing WVCs (i.e., $0 benefit), the final cost for 

this mitigation measure remains at 
185 

$18 per km ($30 per mi) per year.(195) The effectiveness of enhanced wildlife warning signs is 

largely unknown, causing them to be excluded from the analyses. Seasonal wildlife warning 

signs (two signs per km, one sign for each travel direction, and an assumed life span of 10 years, 

no maintenance) may result in a 26 percent reduction of DVCs, and could end up saving 

$10,878 per km ($17,517 per mi) per year. However, keep in mind that these types of signs are 

only applicable in situations where deer (or other large animals) display road crossing behavior 

that is concentrated in space and time. Animal detection systems (life span 10 years, costs 

include maintenance) cost more, but because of their effectiveness in reducing WVCs by 

82 percent, they still result in a positive balance of $3,091 per km ($4977 per mi) per year. 

Too little is known about the costs or effectiveness of animal detection systems linked to an onboard computer or on-board animal detectors for these measures to be included in the analyses. 

Furthermore, the costs and benefits for these mitigation measures depend on the number of 

vehicles equipped with this technology rather than a standard cost per kilometer of road length 

per year. 

There are insufficient data available to evaluate the cost-benefit relationship for roadway lighting 

measures and public information and education programs. Vegetation removal, however, 

demonstrates more potential and may result in a positive balance of $15,437 per km ($24,858 per 

mi) per year. 

Assuming that deer reflectors and mirrors (life span 12.5 years, costs include maintenance) are 

indeed not effective in reducing DVCs, they have a negative balance of $495 per km ($797 per 

mi) per year. The costs for deer whistles are per vehicle rather than per kilometer per year; 

therefore, this mitigation measure was not included in the analyses. However, this measure is not 

considered effective. There are insufficient data available to analyze the cost-benefit relationship 

of audio and visual warning signals in the right of way, olfactory repellents, deer flagging, 

hazing, reducing or replacing road salt, intercept feeding, influencing the species composition 

and the nutritional quality of right-of-way vegetation, and carcass removal. Some carcass 

removal data were available, and costs were expressed in costs per kilometer per year based on 

the removal of five deer carcasses. 

Population culling is cheaper than wildlife relocation or anti-fertility treatment. The costs for 

these mitigation measures are typically expressed in costs per animal. These costs were 

translated to dollars per kilometer per year based on the following assumptions and estimates. 

The width of the zone that the culling, relocation, or anti-fertility treatment would be conducted 

in was based on the home range of white-tailed deer in a suburban environment (43 to 144 ha 

(106 to 356 acres)).(326,398,399) Assuming a home range of 75 ha (185 acres), a deer living within 

977 m (3237 ft) (the diameter of the home range), could cross the road. For a 1-km (0.6-mi)-long 

road section, this zone is 97.7 ha (241 acres) for one road side and 195.4 ha (482 acres) for both 

road sides. Population densities of (suburban) white-tailed deer that are considered a “problem” 

have been estimated at 50–91 individuals per km2

.

(57,400) Assuming a population density of 

70 individuals per km2

, there are 136.8 deer in 195.4 ha. The cost for culling, relocation, and 

anti-fertility treatment was set at $110, $450, and $1,128 (females only), respectively. Assuming 

that a population can only be reduced by 50 percent before the culling, relocation or anti-fertility 

treatment effort becomes much more labor intensive, and the one-time culling and relocation of 

68.4 deer costs $7,524 and $30,780 (reduction of 68.4 deer), respectively. Suburban white-tailed 
186 

deer populations can double their population size every 2–5 years, depending on the 

circumstances.(287) Assuming a closed population (no immigration from adjacent areas), and a 

doubling of population size every 3 years, the culling and relocation effort would have to be 

repeated every 3 years, resulting in an annual cost per km of $2,508 and $10,260 ($4,038 and 

$16,512 per mi) for culling and relocation, respectively. For the anti-fertility treatment it was 

assumed that 80 percent of the females (80 percent of 68.4 female deer is 54.7 female deer, 

assuming an equal sex ratio), would have to be treated annually to stabilize or reduce the 

population density.(287,336) This results in an annual cost for anti-fertility treatment of $61,702 per 

km ($99,300 per mi). The above calculations result in a positive balance for culling and 

relocation and in a negative balance for anti-fertility treatment. Bear in mind that if the 

population is open to immigration from adjacent areas, the effectiveness for the culling, 

relocation, and anti-fertility treatment efforts will be much reduced or potentially eliminated. 

Wildlife fences (life span 25 years, not including maintenance) reduce collisions with ungulates 

by 87 percent on average and have a positive balance of $32,728 per km ($52,702 per mile) per 

year. While insufficient data were available in the literature to evaluate cost-benefit for boulders 

in right of way (as an alternative to wildlife fences), assuming a life span of 80 years, the costs 

were estimated at $2,461 per km ($3,963 per mile) (boulders on both sides of the road) per year. 

The costs for long bridges and long tunnels were set at $781,250 and $1,500,000 per km 

($1,258,051 and $2,415,459 per mile) per year respectively (80-year life span). Both long 

bridges and tunnels have a strongly negative balance. 

To accommodate animal movements from one side of a road to the other, wildlife fences are 

often combined with measures that allow animals to cross the road at grade or to cross under or 

over the road through crossing structures. This section focuses on crossing opportunities for large 

animals only (deer size and up). The cost-benefit analysis assumed one crossing opportunity per 

2 km (1.2 mi) (0.5 crossing opportunity per km) (e.g., along Trans-Canada Highway in Banff 

National Park, Canada), even though higher concentrations of crossing structures for large 

mammals may be required.(352) In addition, gaps were set at a width of 100 m (328 ft), and the 

number of escape ramps between gaps was set at 2 per roadside (1 every 300 m (984 ft) between 

gaps). In addition, the animals could “escape” through the gaps. The number of escape ramps 

between crossing structures was set at 4 per roadside (two immediately next to a crossing 

structure (50 on either side from center), and two in between at 300-m (984-ft)-intervals between 

the crossing structures). The escape ramps on either side of a crossing structure are required 

because of the contiguous wildlife fencing and the assumption that animals will want to cross the 

road most often at the location of the crossing structures, as that should be one of the most 

important criteria for the placement of these crossing structures. The length of the fence was not 

reduced because of gaps or crossing structures because of possible additional fencing at gaps and 

overpasses and the contiguous nature of fencing for underpasses. In addition, for at-grade 

crossings, it was assumed that all deer movements that would have taken place in the 

unmitigated road section (and that resulted in 5 DVCs per km per year), would be funneled 

through these gaps, and that the number of DVCs is not reduced as the result of a potential 

reduction in the number of deer crossings because of the presence of the wildlife fence. 

The life span of the material associated with crosswalks was set at 10 years, while the life span 

for wildlife crossing structures was set at 80 years. The cost for the mitigation measure that 

includes a combination of wildlife fencing and under- and overpasses was based on 0.5 crossing 
187 

structures per km, all of them underpasses except for one overpass every 25 km (15.5 mi). The 

cost for an underpass was set at $200,000, while the cost for an overpass was set at $3,500,000. 

The cost for an escape ramp was set at $8,500 (life span 80 years). Following this analysis, 

wildlife fences with gaps that are mitigated by warning signals have a negative balance, while 

wildlife fences in combination with a crosswalk, an animal detection system, wildlife 

underpasses, wildlife overpasses, or a combination of wildlife under- and overpasses all have a 

positive balance. 

Many of the mitigation measures showed a positive balance. Some of the mitigation measures 

(long tunnels, long bridges, and anti-fertility treatment) showed a strongly negative balance. 

Because of their strongly negative balance, these mitigation measures are not recommended, at 

least not from a strictly monetary perspective. The other mitigation measures had a positive or 

slightly negative balance. However, it is also important to evaluate mitigation measures on the 

balance of the problem that may not have been solved; none of the mitigation measures are 

100 percent effective in reducing collisions, and if a substantial number of collisions and 

associated costs remain, a mitigation measure may not be attractive, despite a potential positive 

balance. 

Figure 60 shows the individual mitigation measures (excluding long tunnels, long bridges, and 

anti-fertility treatment) in relation to their balance and effectiveness. The figure has several 

groupings. Based on the rough estimates in this chapter, wildlife fencing, with or without 

wildlife underpasses or a combination of wildlife underpasses and overpasses, and animal 

detection systems with wildlife fencing have high effectiveness and a high return on investment. 

(identified by solid oval, measures 8, 11, 12, and 14 in figure 60). Animal detection systems 

without wildlife fences or wildlife fences with a high density of wildlife overpasses (identified 

by dashed oval, measures 3 and 13 in figure 60) also have high effectiveness, but their positive 

financial balance is less strong. 
188 

Figure 60. Graph. Annual balance and collision reduction for the different mitigation 

measures (further explanation in text). 
189 

CHAPTER 13. CONCLUSION 

This report has summarized the considerable body of existing knowledge on the impacts and 

mitigations of WVCs. Based on several data sources, it was estimated that one to two million 

WVCs occur annually (focusing on large animals) and that they continue to be a significant 

challenge, costing society billions of dollars. WVCs also result in human injuries and fatalities, 

although this is relatively rare compared to other types of accidents. WVCs are also a serious 

safety risk for animals, not only for the individuals involved, but in some cases for populations or 

the entire species. This report identified 21 federally threatened and endangered species for 

which road mortality was identified as one of the major threats to their long-term survival. 

This report reviewed over 34 mitigation measures aimed at reducing WVCs. Wildlife fencing, 

with or without wildlife crossing structures, animal detection systems, and long tunnels or 

bridges were found to provide the greatest reduction of WVCs. Site-specific conditions will 

dictate the appropriate mitigation measure(s), as there is no single, low-cost solution for WVCs 

that can or should be applied everywhere. A successful mitigation strategy requires a detailed 

analysis of the problem and the local situation and often involves a combination of different 

types of mitigation measures. Moreover, improved objective evaluation of the mitigation 

measures will help States and others make better informed decisions. 

191 

APPENDIX: EXPERTS CONSULTED FOR ENDANGERED SPECIES ACT LIST 

Susan Hagood (Chelonians) 

The Humane Society of the United States 

2100 L Street NW 

Washington, DC 20037 

SHagood@hsus.org 

David H. Nelson, Ph.D. (Alabama red-bellied turtle (Pseudemys alabamensis)) 

Department of Biological Sciences 

University of South Alabama 

Mobile, AL 36688 

(251) 460-6331 (phone) 

(251) 414-8220 (fax) 

dnelson@usouthal.edu 

Bruce Porter (Alabama red-bellied turtle (Pseudemys alabamensis)) 

USFWS ECOLOGICAL SERVICES-DAPHNE 

1208-B Main Street 

Daphne, AL 36526 

(251) 441-5864 (phone) 

(251) 331-0835 (cell) 

(251) 441-6222 (fax) 

Kathleen Misajon (Hawaiian goose (Branta sandvicensis)) 

Hawai'i Volcanoes National Park 

P.O. Box 52 U.S. 

Hawaii 96718 

(808) 985-6194 (phone) 

Kathleen_Misajon@nps.gov 
192 

Brian Yanchik (Indiana bat (Myotis sodalis)) 

FHWA Resource Center 

ENVIRONMENT TEAM 

Biology/Water Quality Specialist 

104 Spring Meadows Drive 

Summerville, SC 29485 

(443) 522-9446 (phone) 

brian.yanchik@fhwa.dot.gov 

Paul Garrett (general, Indiana bat (Myotis sodalis)) 

USDOT, Federal Highway Administration 

HEPN-30 

555 Zang St., Room 400 

Lakewood, CO 80228 

(303) 969-5772 x332 (phone) 

(303) 969-6727 (fax) 

Paul.garrett@fhwa.dot.gov 

Mary E. Gray (general coastal California gnatcatcher (Polioptila californica), 

Columbian white-tailed deer (Odocoileus virginianus leucurus) 

Federal Highway Administration 

Office of Natural and Human Environment 

711 S. Capitol Way Suite 501 

Olympia, WA 98501 

(360) 753-9487 (phone) 

Mary.Gray@fhwa.dot.gov 
193 

Trevor A. Kinley (Woodland caribou (Rangifer tarandus caribou) 

Sylvan Consulting Ltd., 

RR5 3519 Toby Creek Road 

Invermere, BC 

V0A 1K5, Canada 

sylvan@rockies.net 

Frank J. Mazzotti (American crocodile) 

Associate Professor of Wildlife Ecology 

Department of Wildlife Ecology and Conservation 

Fort Lauderdale Research and Education Center 

3205 College Avenue 

Davie, FL 33314 

(954) 577-6338 (phone) 

fjma.at.ufl.edu 

E. Claiborne Barnwell, P.E. (Gopher tortoise) 

Mississippi Department of Transportation 

Environmental Division Engineer 

(601) 359-7920 (phone) 

(601) 359-7355 (fax) 

(601) 946-7854 (cell) 

cbarnwell@mdot.state.ms.us 
194 

Matthew J. Aresco, Ph.D. (Gopher tortoise, Alabama red-bellied turtle (Pseudemys 

alabamensis)) 

Conservation Director 

Nokuse Plantation 

13292 Co. Highway 3280 

Bruce, FL 32455 

(850) 559-0483 (phone) 

(850) 562-3093 (phone) 

(850) 267-4960 (fax) 

aresco@lakejacksonturtles.org 

Laurie Fortin (wildlife rehabilitation numbers) 

DEP, Wildlife Division 

79 Elm St. 

Hartford, CT 06106 

(860) 424-3963 (phone) 

(860) 424-4078 (fax) 

laurie.fortin@po.state.ct.us 

John Palis (Flatwoods salamander) 

Palis Environmental Consulting

P.O. Box 387 

Jonesboro, IL 62952 

jpalis@yahoo.com 
195 

D. Bruce Means, Ph.D. (Flatwoods salamander) 

President and Executive Director 

Coastal Plains Institute and Land Conservancy 

1313 Milton Street, Tallahassee, FL 32303 

(850) 681-6208 (phone) 

(850) 681-6123 (fax) 

and 

Adjunct Professor 

Department of Biological Science 

Florida State University 

Tallahassee, FL 32303 

www.brucemeans.com 

means@bio.fsu.edu 

Dave Johnston (California tiger salamander) 

California Department of Fish and Game 

(831) 466-0234 (phone) 

DJOHNSTON@dfg.ca.gov 

Alison Michael (Canada lynx) 

U.S. Fish & Wildlife 

755 Parfet St, Ste 361 

Lakewood, CO 80215 

(303) 275-2378 (phone) 

Alison_Michael@fws.gov 
196 

Phil Delphey (Canada lynx) 

U.S. Fish and Wildlife Service 

Twin Cities Field Office 

4101 E. 80th Street 

Bloomington, MN 55425 

(612) 725-3548 ext. 206 (phone) 

(612) 725-3609 (fax) 

Phil_Delphey@fws.gov 

Dan Smith (crested caracara) 

Western Transportation Institute 

Montana State University 
197 

ACKNOWLEDGEMENTS 

The authors wish to thank the project committee members, Brian Allen, Dennis Durbin, Paul 

Garrett, Mary Gray, Carol Tan, Michael Trentacoste, and Abdul Zineddin, for their help and 

support for this project. 

The authors would also like to thank the Technical Working Group for volunteering their time to 

help make a better product: Bill Branch, Michael Pawlovich, Scott Jackson, Susan Hagood, 

Brent Haglund, Sandy Jacobson, and Keith Knapp. 

Special thanks to Dr. Yusuf Mohamedshah from HSIS, who was vital in the preparation of this 

report. He promptly addressed requests for data and provided valuable technical assistance as 

questions arose. 

The authors would also like to thank Matthew Aresco, Claiborne Barnwell, Phil Delphey, Paul 

Garrett, Mary Gray, Susan Hagood, Dave Johnston, Trevor Kinley, Frank Mazzotti, Bruce 

Means, Alison Michael, Kathleen Misajon, David Nelson, John Palis, Bruce Porter, Dan Smith, 

and Brian Yanchik for sharing their expertise with regard to specific species. 

In addition, thanks go out to the technical editors and reviewers at WTI and Louis-Berger: Carol 

Diffendaffer, Carla Little, Catherine Heidkamp, Jerry Stephens, and Edward Samanns as well as 

to Susan Gallagher and James Mehlos at WTI for assistance with the annotated bibliography. 

199 

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