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APPENDIX A
Priority Tables and Plan of Action
Top Five Priorities by Nation province-wide and regional bases. When transportation pro-
fessionals and scientists seek readily available databases or
Tables 37 and 38 show the top five priorities of the United systematic methodologies for gathering data so that they can
States and Canada for restoring wildlife movement across incorporate ecological data into transportation programs or
roads. mitigation models and measures, they are apt to find that
long-term databases, such as those containing wildlifevehicle
collision data are usually not associated or linked with spatially
Top Five Priorities of Engineers/ accurate locations, road geometrics, or environmental data.
Analysts/GIS Specialists Additionally, databases may be in a variety of formats. For
Table 39 shows the top five practice and research priorities example, wildlifevehicle collisions data are contained in
of engineers, analysts, and GIS specialists. highway patrol reports, and in forms filled out by highway
maintenance crews. Important data such as the location and
maintenance schedules for culverts and bridges are not always
Top Five Priorities of Planners electronically available. There are also inconsistencies among
states and provinces concerning the dissemination of critical
Table 40 shows the top five research and practice priorities
wildlife habitat needs, and the identification of priority areas
of planners.
for conservation. If these data were readily available in
electronic databases similar to each state's Natural Heritage
program but in greater detail, DOTs and MoTs would be
Top Five Priorities of Natural
better able to incorporate wildlife and ecosystem priorities
Resource Professionals--Overall
into the planning stages of transportation programs and indi-
Table 41 shows the top five research and practice priorities vidual projects. Additionally the research team found that
of natural resource professionals. guidelines for planning and installing wildlife crossings are
nonexistent for most states and provinces. In summary, the
Plan of Action for Priorities research team have found a lack of (1) long-term and accurate
databases on wildlifevehicle collisions or roadkill carcass
Practice Gaps and Priorities locations that are electronically based and standardized, (2) a
nation-wide standardized method for state and provincial
Ecological
wildlife agencies to incorporate wildlife locations and their
Agencies responsible for creating wildlife mitigation habitats and needs in a cohesive document readily available
measures along transportation corridors would profit by for other agencies to work with, and (3) widely available
standardizing and institutionalizing practices that aid in guidelines for developing and maintaining wildlife crossings
the development of mitigation techniques. and other mitigation measures. Without standardized and
There is a need to standardized methods for collecting and institutionalized practices informed by accurate, complete,
recording data, the development and communication of state and documented databases, transportation professionals find
and provincial wildlife habitat conservation needs, and the it difficult to collect and analyze data on wildlifevehicle col-
development of wildlife crossing guidelines on state- and lisions and roadkill carcass locations, include ecological and
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Table 37. Top five priorities for restoring wildlife movement
across roads in the United States and Canada.
United States Top Priorities Rank Canada Top Priorities
Incorporate wildlife mitigation needs early in
the DOT/MoT programming, planning, and 1 Same
design process
Combine animal-friendly mitigation methods
such as wildlife crossings, fences, escape
2 Same
ramps, and gates, rather than using one
method
Use conservation plans and connectivity
analyses to inform the transportation
programming/planning/design process on 3 Same
where mitigation is needed and how it may be
carried out
Use standardized and vetted protocols for
Establish effective communication and
4 collecting and recording roadkill carcass and
collaboration among stakeholders
wildlifevehicle collision data
Incorporate into plans and schedules wildlife
crossing options that can be accomplished by Establish effective communication and
5
maintenance crews simply by retrofitting collaboration among stakeholders
existing facilities
Table 38. Top five research priorities for restoring wildlife movement
across roads in United States and Canada.
United States Top Priorities Rank Canada Top Priorities
Understand better the dynamics of animal
use of mitigation structures (such as what
1 Same
works and what does not) and disseminate
this information
Develop and summarize alternative, cost-
Standardize spatially accurate roadkill carcass
effective wildlife crossings designs and the 2
and wildlifevehicle collision data collection
principles they are based on
Develop wildlife crossing designs and
Develop and summarize alternative, cost-
guidelines for the full suite of animals in an
3 effective wildlife crossings designs and the
area to help facilitate permeability for many
principles they are based on
species
Develop guidelines to decide when wildlife
Develop state-based habitat connectivity
4 mitigation is necessary (both mandated and
analyses for every state
voluntary)
Develop prototype animalvehicle collision
Develop a standardized monitoring protocol safety models to predict where wildlifevehicle
5
to assess crossing effectiveness collision hotspot areas are and may be on
future roads
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Table 39. Top five research and practice priorities of engineers/analysts/
GIS specialists.
Rank Practice Priorities
Incorporate wildlife mitigation needs early in the DOT/MoT programming, planning, and
1
design process
2 Establish effective communication and collaboration among stakeholders
Combine animal-friendly mitigation methods such as wildlife crossings, fences, escape
3
ramps, and gates, rather than using one method
Use conservation plans and connectivity analyses to inform the transportation
4 programming/planning/design process on where mitigation is needed and how it may be
carried out
Incorporate into plans and schedules wildlife crossing options that can be accomplished
5
by maintenance crews simply by retrofitting existing facilities
Research Priorities
Understand better the dynamics of animal use of mitigation structures (such as what
1
works and what does not) and disseminate this information
Develop and summarize alternative, cost-effective wildlife crossings designs and the
2
principles they are based on
Develop guidelines to decide when wildlife mitigation is necessary (both mandated and
3
voluntary)
4 Develop a standardized monitoring protocol to assess crossing effectiveness
Develop wildlife crossing designs and guidelines for the full suite of animals in an area to
5
help facilitate permeability for many species
safety data into the planning process, create mitigation meas- wildlife needs. The U.S. Transportation Equity Act for the 21st
ures for wildlife, or find ways to integrate existing mainte- Century (TEA-21) requires that planners develop long-range
nance and upgrade schedules with mitigation opportunities. plans and short-range programs that consider projects and
strategies that, among other things, will protect and enhance
Priority. Create standardized protocols for collecting the environment. However, the act provides no guidance on
roadkill carcass locations and wildlifevehicle collision data. how planners should meet these requirements.235 Typically, if
This information is crucial in helping to determine where ecosystem and wildlife are considered, it is late in the devel-
wildlife mitigation measures to reduce wildlifevehicle opment of a transportation project. This can often lead to de-
collision are needed. Departments and Ministries of Trans- lays in the permitting process, incurring the expenditure of
portation would benefit from the collection of data by additional funds. This is not in the best interest of the ecolog-
standardized, accurate methods that could be incorporated ical resource, the transportation agencies, or the public. The
with future road improvements, road building, and reduc- research team strongly suggests these analyses be incorporated
tions in wildlife-related crashes. (See priorities above under early in the development of long-range transportation plans.
safety models). The research team points to two successful Planners in Oregon, South Dakota, Colorado, and North
efforts: Maine has a wildlifevehicle collision reporting Carolina for example, extensively consider ecosystem conser-
program that is geo-referenced and mapped for the public,156 vation during planning processes.235 Vermont has a policy of
and British Columbia has maintained a long-term database of addressing wildlife and fish needs in future transportation
wildlifevehicle collisions that is analyzed in order to create projects prior to regulatory intervention (C. Slesar and
appropriate measures to reduce these crashes.211 J. Austin, personal communication) and Montana state and
federal agency personnel have worked together to create the
Priority. Create continent-wide guidelines and standards largest, most comprehensive sets of wildlife mitigation meas-
for determining when during the transportation planning ures over one highway in the United States.205 This priority is
process agencies should assess programs and projects for linked with the priorities to implement statewide connectivity
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Table 40. Top five research and practice priorities of planners.
Rank Practice Priorities
Combine animal-friendly mitigation methods such as wildlife crossings, fences, escape
1
ramps, and gates, rather than using one method
Incorporate wildlife mitigation needs early in the DOT/MoT programming, planning, and
2
design process
Use conservation plans and connectivity analyses to inform the transportation
3 programming/planning/design process on where mitigation is needed and how it may be
carried out
Incorporate into plans and schedules wildlife crossing options that can be accomplished
4
by maintenance crews simply by retrofitting existing facilities
5 Establish effective communication and collaboration among stakeholders
Research Priorities
Understand better the dynamics of animal use of mitigation structures (such as what
1
works and what does not) and disseminate this information
Develop and summarize alternative, cost-effective wildlife crossings designs and the
2
principles they are based on
Develop wildlife crossing designs and guidelines for the full suite of animals in an area
3
to help facilitate permeability for many species
Develop standardized inventories of wildlife crossings by state for better management
4
and maintenance of these crossings, and to better assess the need for future crossings
Three priorities tied for fifth rank:
Develop a standardized monitoring protocol to assess crossing effectiveness
5 Develop guidelines to decide when wildlife mitigation is necessary (both mandated
and voluntary)
Increase our understanding of the effects of road density on wildlife populations
analyses, enacting policy to mandate these actions and the pri- Wildlife Habitat Conservation System" documentation, its
ority below, the development of statewide wildlife habitat statewide "Strategic Habitat Conservation Areas" program,
conservation plans. and the "Biodiversity Hot Spots," which are all scientific
efforts that are translated into GIS data layers and are incor-
Priority. Incorporate state- and province-wide maps porated into Florida DOT's Environmental Screening Guide
and conservation plans for critical wildlife habitat needs into (V. Sharpe personal communication).92
transportation planning. The U.S. Fish and Wildlife Service
asked state wildlife agencies to complete their wildlife habitat Priority. Create and update guidelines for considering,
conservation plans by October 2005. These plans will include placing, designing, and constructing wildlife crossings. This is
GIS-generated maps showing ranges and critical habitats of a priority for the practice as well as the science of road ecology.
species of concern and will greatly assist DOTs and MoTs in This priority is linked to the development of monitoring pro-
planning mitigation to maintain or restore ecosystem grams to assess the effectiveness of mitigation measures.196
integrity and viable wildlife populations. The successes of More detailed statements related to this priority can be viewed
current programs may be used to help guide further actions. above under guidelines in research priorities. Examples of
For instance, Florida's Fish and Wildlife Commission has current guideline efforts include the set of guidelines created
communicated wildlife needs through its Integrated Wildlife for the installation of amphibian and reptile tunnels in New
Habitat Ranking System,76 the "Closing the Gaps in Florida's England,130 standards created for river and stream crossings
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Table 41. Top five research and practice priorities
of natural resource professionals.
Rank Practice Priorities
Incorporate wildlife mitigation needs early in the DOT/MoT programming, planning, and
1
design process
Combine animal-friendly mitigation methods such as wildlife crossings, fences, escape
2
ramps, and gates, rather than using one method
Use conservation plans and connectivity analyses to inform the transportation
3 programming/planning/design process on where mitigation is needed and how it may be
carried out
4 Establish effective communication and collaboration among stakeholders
Incorporate into plans and schedules wildlife crossing options that can be accomplished
5
by maintenance crews simply by retrofitting existing facilities
Research Priorities
Understand better the dynamics of animal use of mitigation structures (such as what
1
works and what does not) and disseminate this information
Develop and summarize alternative, cost-effective wildlife crossings designs and the
2
principles they are based on
Develop wildlife crossing designs and guidelines for the full suite of animals in an area to
3
help facilitate permeability for many species
4 Develop state-based habitat connectivity analyses for every state
5 Develop a standardized monitoring protocol to assess crossing effectiveness
for fish,236 and Colorado's guidelines for the placement of most helpful. This is an ongoing priority that needs the con-
crossing opportunities for wildlife.14 The United States has tinued guidance and attention from a multi-agency committee
learned and will continue to learn from one of the agency lead- that has credibility with transportation professionals.
ers in wildlife crossings, Parks Canada, who has taken the lead
for the North American continent in instituting and evaluat- Priority. Maintenance activities on crossings need to be
ing wildlife crossings. recorded in standardized documentation schedules. If struc-
tures and accompanying mitigation features such as fences
Priority. Funding and maintenance for an outlet that are not maintained, their effectiveness often decreases.71
communicates the standardized guidelines is a priority. Guide- Documentation of maintenance schedules, methods, and
lines could be communicated and updated through the use of costs provides assurance that the structures are fulfilling
agency-based websites. As knowledge improves and evolves, so their purpose and can help in establishing maintenance
should the guidelines be updated to reflect this or they risk be- needs for future mitigation measures.
coming obsolete. There is a need for meaningful partnerships
among federal agencies and associations to commit resources Priority. Create alignment specifications for effective mit-
and personnel to maintain useful websites. Ideally, these sites igation efforts that link wildlife crossings with fences and right-
should provide extensive searchable literature databases, of-way (ROW) escape ramps. Certain fence types are known to
annotated bibliographies, research reviews linked to projects, not be wildlife friendly, and wildlife need to be able to escape if
as well as the previously mentioned guidelines, and any deci- trapped on the roadway. Evidence from studies conducted at
sion guide associated with NCHRP Project 25-27. Linking to Utah State University suggest that the rectangular mesh design
existing websites (i.e., the Wildlife Crossings Guidekit, the used in most "deer-proof" fencing applications can result in
DeerVehicle Crash Information Clearinghouse) would be the death of juvenile animals who become trapped in the fence.
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The barbed wire arrangement used in lower fences is also prob- mandate the use of standardized and effective methods to
lematic for species such as pronghorn antelope. The research maintain and promote permeability and connectivity of the
team urges standards for animal-friendly fences, for example, a landscape for wildlife are to be enacted.
different mesh size for exclusion fences. Larger animals often If transportation and natural resource agencies continent-
access the ROW even if it is fenced. Measures (such as earthen wide are to address the pressing issues of landscape fragmen-
escape ramps) are needed to allow them to escape the road tation and effects of road transportation networks on species,
ROW in the presence of exclusion fencing. Fencing mitigation it is essential to go beyond the individual transportation proj-
efforts need to incorporate escape ramps in order to be maxi- ects and individual species approaches of the past.98 There is
mally effective. Ungulate (deer, elk, and moose) are much more a need for national-level, firm, and legal guidelines that man-
inclined to use escape ramps than "squeeze-through" steel gates date the incorporation of wildlife and ecosystem considera-
to escape the ROW. Additionally, in areas with rugged topog- tions early in the long-range transportation planning stage.
raphy, the typical perpendicular ramp-fence alignment may There is also a need to correct the basic inconsistencies
not be most effective. Ramps placed "in-line" with the fence among states and provinces in their practices and policies to-
may be a desired alternative. There is a need to explore other es- ward protecting wildlife and re-establishing connectivity
cape mechanisms that could be created for large and small an- across the landscape. To this end it is necessary to establish
imals, e.g., badger and small-mammal tunnels. The research common goals and objectives that state/provincial and fed-
team also encourages the practice of implementing alternative eral governmental agencies can agree upon and accomplish
and innovative designs. These could be developed in an adap- in order to increase permeability of transportation corridors
tive management context of learning from doing; a context for wildlife.
where practice is tied to research in an explicit fashion. This ap-
proach is currently in use in developing wildlife mitigation Priority. Legislation that enables and funds mandatory
measures in Arizona.73 For small animals that are not deterred planning and mitigating for wildlife along transportation
by exclusion fences, the research team suggests the adoption of corridors is desirable. The research team believes this is
jersey barriers with wildlife scuppers (openings in the barrier attainable and point to two currently successful programs:
that allow for passage of small animals and water movement) Florida and The Netherlands. In both places, laws and poli-
or low barriers that direct animals to small tunnel-like passages. cies have been passed and programs funded to develop maps
Additionally, research has shown higher roadkill levels often of ecological networks and to identify places where roads
occur at the end of the fenced mitigation, the so-called "end-
fragment or fracture these networks, and where specific areas
of-fence" problem.71 The research team considers it a priority
and transportation projects for mitigation and compensation
to address fence designs, the end-of-fence problem, and ramp-
have been identified.11,94 In order for similar actions to be
fence alignments in order to increase the effectiveness of these
applied across the United States and Canada, there is a need
common mitigation structures.
for fully funded federal-level mandates or strong incentive
Priority. Culvert and bridge maintenance schedules programs that authorize and institutionalize methods to
need to be made available in electronic format so upgrade and identify, plan, and mitigate for landscape connectivity along
replacement projects can be coordinated with mitigation transportation corridors. Funding for this effort may be
measures. Existing transportation infrastructure could be attained from TEA-21, FHWA research funds, and dedicated
retrofitted for wildlife and fish during routine maintenance state funds.11,79
and upgrading. Regional protocols could be developed to in- The research team suggests that leadership for these efforts
tegrate culvert, bridge, and fencing maintenance schedules to coordinate multi-agency standards that help maintain and
with the needs of aquatic and terrestrial wildlife in the area. promote permeability and connectivity of the landscape for
Protocols that retrofit culverts for fish passage are available in wildlife come from a strong federal-state/provincial partner-
several states.16,157,164 ship. Likely partners include the U.S FHWA and Transport
As more is learned about efforts by states and provinces to Canada as well as the U.S. Fish and Wildlife Service and Envi-
create standardized collection methods and data storage, and ronment Canada, coupled with transportation and wildlife
to create guidelines for wildlife mitigation measures, the re- representatives from the states and provinces. Additional
search team believes these efforts can be implemented across organizations might well include the American Association of
the continent. State Highway and Transportation Officials (AASHTO), the
U.S. Forest Service, the U.S. Environmental Protection Agency,
and the Bureau of Land Management.11 Non-governmental
Policy and Planning
organization (NGO) participation would provide a public
National, state, and provincial authorities at the highest input, and several have been active in this arena (Defenders of
levels need to be fully engaged if policies and guidelines that Wildlife, the BC Conservation Foundation, and The Nature
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Conservancy). A successful partnering arrangement might finds it is a key component to successful wildlife mitigation
partition duties with wildlife and natural resource agencies programs. The most successful and far reaching wildlife-
providing ecological guidelines as well as measures of success, transportation mitigation programs across the United States
while the FHWA and Transport Canada could standardize and and the world have communications networks (such as the
coordinate compliance with state and provincial DOTs/MoTs, Infra Eco Network Europe [IENE]) that have been developed
while at the same time linking incentives with funding. to coordinate information,91 include ecosystem-level needs in
The research team strongly encourages funding incen- transportation planning (IENE's Cost 341 effort),129 and
tives in these mandates for transportation agencies to garner support for providing measures for wildlife in trans-
(1) conduct connectivity studies, for example, as Washington portation systems.11 From these and other examples of suc-
State DOT has done 212; (2) fund GIS data development cesses within states and provinces, the research team describes
(which many DOTs/MoTs have done); (3) continue data- in the following paragraphs two priorities that relate to infor-
partnering with other agencies, which most states do but mal and formal communication.
which can be improved 91; (4) incorporate wildlife habitat
connectivity maps in long-range transportation program Priority. Increased informal communication opportu-
planning such as Washington and Florida have done; nities among transportation professionals, on-the-ground
(5) mitigate for wildlife in most transportation projects transportation workers, and ecologically trained profes-
(e.g., such as what is done in Vermont); and (6) remain sionals are necessary. Some notable successes include the
consistently committed to this goal over time. Such a International Conference on Ecology and Transportation
specifically defined approach would help to level the bi-annual events and the well-circulated proceedings from
current inconsistencies among states and provinces and those conferences; the Center for Transportation and the
promote continent-wide permeability for wildlife across Environment at North Carolina State University and its well-
transportation corridors. maintained website and list server; the Wildlife Crossings
Guidekit website initiated by the U.S. Forest Service and
housed at Utah State University; the Deer-Vehicle Crash
Communication
Information Clearinghouse at the University of Wisconsin;
Improved communication among transportation pro- and other events, publications, and websites dedicated to
fessionals, on-the-ground transportation workers, scien- highlighting and exploring wildlife and transportation issues.
tists, activists, and the public is needed to help ensure that The research team encourages transportation and wildlife
wildlife crossings measures and other actions to maintain professionals to communicate using the above-mentioned
ecosystem permeability across transportation networks are methods and other less formal means to learn about ecologi-
driven by the most effective and efficient methodologies. cal impacts of roads, successes and failures of research and
Road ecology is a rapidly developing field of study that re- practices, and innovative ideas and for increased opportuni-
lies on communication among researchers and practitioners ties to include wildlife and ecosystem needs into the planning
from around the world. While great gains have been made in and designing of roads. Increased communication opens
this field in the past 10 years, the research team has observed opportunities to coordinate mitigation for ecosystem and
common gaps in communication within and among agencies wildlife needs in the development of long-range programs and
and other professionals and the public that directly affect the project plans long before these plans became fully developed
ability to place and maintain wildlife crossings. It is impera- and budgeted. There is a strong need for direct communica-
tive that study results and practices that are both successful tion between biologists and on-the-ground transportation
and unsuccessful are communicated as quickly and effectively workers. These workers are the critical link to accurate data
as possible in order for transportation planners and engineers collection and are often the source of innovative design solu-
to build transportation corridors that are less damaging to tions. They are often very interested in wildlife and would like
wildlife. Although not universal, the lack of communication feedback on the effectiveness of mitigation measures that they
and data sharing among agencies at federal and state levels design and install. They can also provide crucial information
that relate to long-range planning; the collection of accurate to biologists such as maintenance schedules for bridges, cul-
roadkill and wildlifevehicle collision locations; and the verts, and upgrades to roads. If these schedules were coordi-
effective placement, construction, monitoring, and mainte- nated with environmental managers and biologists, ideally
nance of mitigation structures hampers progress. Addition- these already planned projects could present opportunities to
ally the lack of funding to coordinate such communication is retrofit these structures for the movement of wildlife, fish, and
problematic. ecological processes. With over 575,000 bridges in the United
The need for communication has been a common theme States and as many as 40,000 of these needing repair or
in the priorities listed in this document. The research team replacement in the next two decades,253 there are literally tens
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of thousands of opportunities to coordinate such efforts to to quickly and efficiently bring about change in the practices
improve landscape connectivity. associated with transportation and wildlife.
Priority. Increased formal communications among
states, provinces, and countries are necessary. The research Research Gaps and Priorities
team believes these communications are necessary to help
Safety
this field move forward concerning the development of ef-
fective mitigation structures. There are several avenues for Existing wildlifevehicle collision prediction models re-
increased communications including clearinghouses, con- quire further development to be effectively used for safety
ferences, proceedings, publications, and federally sponsored analyses tasks such as identifying wildlife collision-prone
websites such as FHWA's Exemplary Ecosystem Initiatives locations on both existing roads and new roads, evaluating
and Wildlife Protection--Keeping it Simple, the TRB's the collision reduction effectiveness of mitigation meas-
Transportation Research Information Services database, ures, and conducting cost-effectiveness analyses of poten-
AASHTO's Center for Environmental Excellence, and tial mitigation projects.
Standing Committee on the Environment, British Columbia There is a need for the development of more reliable
Conservation Foundation's Wildlife Vehicle Accident wildlifevehicle collision prediction models that would in-
Prevention Program, and Parks Canada's Highway Mitiga- form transportation professionals about collision-prone
tion Research Program. The research team suggests a areas, not only on existing roadways, but also on new road-
clearinghouse for projects across North America. This ways in the planning or design stage. These models would
central location could be maintained by the FHWA and assist in systematic screening of the road network, which is
would house information on past, current, and future proj- routinely done in jurisdictions, in order to identify specific lo-
ects with specifics that would be of interest to other agencies cations that merit further investigation as potential locations
and locations. The research team suggests additional oppor- for crossing, fencing, and other mitigation measures such as
tunities to share information over the entire continent for those that address driver behavior (e.g., reduced speed limits).
example increasing the number of public meetings such as These same predictive models are also required to assess,
ICOET and regional ecology and transportation confer- retrospectively, the collision reduction effectiveness of coun-
ences, for instance the Northeast Wildlife and Transporta- termeasures aimed at reducing wildlifevehicle collisions. The
tion Conference. The proceedings of these meetings are a types of models required for these purposes ideally would
major source of information on developments in this field. estimate the expected frequency of collisions. Most current site-
The proceedings and other information could be published specific models estimate the probability of a site being a "high-
in a way that professionals from a variety of non-ecological collision location," which is subjectively defined, and therefore
transportation interests such as planners, administrators, does not provide an estimate of the expected collision fre-
and engineers, would be notified electronically of their exis- quency.15,88,124 These "probability" models typically include
tence. These proceedings and other publications would help variables that necessitate field data collection and thus they
promote the science base of road ecology if they gave easily cannot be applied for network-wide screening because of data
accessed sets of definitions for all professionals to under- limitations in state databases.169 Additionally, most current
stand. Communication could also be improved if long-term wildlifevehicle collisions prediction models are limited in
funding was available to maintain websites dedicated to their ability to accurately describe the general cause-and-effect
wildlife crossings and other related mitigation measures. relationships among variables that affect collisions and hence
Linking them to the FHWA website is a step in the right are limited in their ability to inform practitioners who would
direction. Finally, professionals have a responsibility to like to be proactive in predicting where wildlifevehicle colli-
educate and help the public become aware of issues sions are most likely to occur. The development of integrated
concerning wildlife mortality, crossings, landscape frag- models is hampered by (1) the lack of a national protocol for
mentation versus permeability, and public safety. The collecting wildlifevehicle collision as well as roadkill carcass
research team encourages transportation agencies to com- data; (2) the limited number of reliable long-term databases
municate with the public the needs for wildlife crossings of wildlifevehicle collisions and roadkill carcass data; (3) the
projects, the development and completion of mitigation lack of crash site data or other important model inputs such
measures, and the results of monitoring projects. In these as highway variables (geometrics) and ecological variables
communications, the research team strongly encourages (e.g., topography and existence of migration routes); and
scientific messages pertaining to the issues of fragmentation (4) the lack of knowledge of wildlife exposure (i.e., the change
and connectivity to help the public understand. The re- over time of the number or density of animals in enough prox-
search team encourages progress in all these areas in order imity to a road to be potentially struck by a motor vehicle). It is
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apparent (to the research team) that spatial accuracy is a defin- across roads, such as presence of nearby fencing, culverts and
ing characteristic of these databases. The research team bridges, presence and characteristics of wildlife underpasses,
believes tremendous progress can be made in this research adjacent land cover, distance to cover from the edge of the
area if the following priorities can be accomplished. road, topography, human use of the area, species present, and
standard road geometrics. The research team believes that
Priority. Develop a strategic plan that is a well defined, in- assembling information on variables such as these would
terdisciplinary, and multijurisdictional strategy to address the provide much improved databases that could in turn be used
wildlifevehicle collision problem and its complexities.142 There to improve understanding of the causes of wildlifevehicle
are dozens of attempts to model wildlifevehicle collisions with collisions and result in models that reflect this understanding
different methods, in different regions over many different sit- and recommendations that would reduce these collisions and
uations, and yet the approaches tend to be piecemeal rather wildlife roadkill in general.
than building on one another. In order to bring the develop-
ment of wildlifevehicle collision predictive models to a level Priority. Create standardized electronic inventories of ex-
where they are applicable over large regions, the combined ef- isting crossings, bridges, and culverts and their geo-referenced
forts of professionals in several disciplines is desirable. The re- locations in order to evaluate their potential for use by wildlife.
search team believes that the current pooled-fund proposal 142 Wildlife use crossings that are intended for them as well as
for the creation of a Deer-Vehicle Crash Information and Re- transportation infrastructure such as culverts and bridge
search Center is a step in the right direction for bringing the past underpasses in order to avoid motor vehicles. Modelers,
and future work together in one central location and for the de- engineers, and biologists alike would be better able to distin-
velopment of a cohesive strategy to address this issue. guish between the need for additional crossings or mitigation
measures versus the modification of existing structures if there
Priority. Standardize and improve the collection of were state- and province-based electronic inventories of
roadkill carcass data and wildlifevehicle collision data. Data existing structures (culverts, underpasses) that could be ana-
on roadkills and wildlifevehicle collisions are currently lyzed as part of a safety model for their potential and current
collected by a variety of methods. The research team knows use by wildlife.
of only one database that has the spatial accuracy needed to
produce reliable ecological models that link environmental Priority. Develop methods to estimate the densities of
variables with road mortality of animals (the Parks Canada animals near transportation corridors in order to calculate the
database). The research team suggests a roadkill collection risk of collision or exposure for certain stretches. The research
protocol and a wildlifevehicle collision location protocol be team realizes that calculating "exposure" is a daunting task,
standardized across the nations or within regions in order to and that surrogate measures, such as species density, daily
obtain spatially accurate reliable databases not only for movement behavior, seasonal migration patterns, annual har-
modeling efforts, but also to assist in state Departments of vest records (see Mysterud177), and behavior near roads, would
Transportation (DOTs) and provincial Ministries of Trans- need to be linked with spatial landscape data to approximate
portation (MoTs) efforts to reduce collisions and roadkill. "exposure." This priority would entail working with state
Data collection on collision and carcass sites could provide wildlife agencies in estimating and mapping where the most
more accurate information if they were geo-referenced, i.e., "high risk" animals are, i.e., deer, elk, and moose.
identified with global positioning systems that accurately
specify the collisioncarcass location. These accurate loca- Priority. Develop research guidelines on evaluating the
tions are critical if the research team is to assess the entire effectiveness of wildlife crossings from a vehicleanimal col-
suite of other factors believed to affect collisions. lision perspective. The guidelines should demonstrate proper
analysis methods and provide guidance on the monitoring of
Priority. Include spatially accurate information on off- treatment sites. Monitoring of wildlife crossings should in-
roadway variables into highway safety models used to predict clude data on pre- and post-construction wildlifevehicle
wildlifevehicle collisions. If these data are not available, collisions and roadkills. In order for models to evaluate the
safety models could only be developed with only information effectiveness of the full suite of wildlife crossings measures,
pertaining to roads (road geometrics and traffic volumes). monitoring efforts of these crossings measures need to be
Such models, though still useful as predictive models, are lim- expanded. When crossings are installed, monitoring efforts
ited in their ability to advance understanding and capability have typically focused on documenting the number of ani-
to predict where and when wildlifevehicle collisions will mals and species using the structures. The research team sug-
occur. Off-road information that would be considered in a gests that monitoring programs also include an analysis that
model include variables known to affect wildlife movement documents pre- and post-construction wildlifevehicle col-
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lisions, roadkill carcass data, traffic volume, and possible standardized cost-effective procedures. Although there are
wildlife exposure. Proper analysis methods need to account dozens of wildlife crossings designs available, there are a stan-
for numerous difficulties in analyzing collision data includ- dard dozen or so in most common use. Through research and
ing regression-to-the-mean effects, spillover effects, differ- practice, option-enabled alternatives could be explored that
ences in crash investigation and reporting practice between may allow added permeability of the landscape over and under
jurisdictions when amalgamating data and exposure changes transportation corridors, while at the same time minimizing
between before-after periods. costs incurred.
Cost-effective designs for wildlife crossings need to be de-
Ecological Considerations
veloped through research and novel on-the-ground practices.
An analysis of cost-effectiveness is a requirement for the The genetic implications of the effects of roads on popu-
consideration of most mitigation measures for wildlife. If flexi- lations are largely unknown, but theoretical and empirical
ble standards or "standardized option-enabled" procedures and evidence suggest that they fragment populations and their
innovative designs could be created, there would be more habitats.
opportunities to incorporate wildlife mitigation measures in Transportation corridors are affecting the genetics of
transportation projects. The term "standardized option- wildlife populations, the consequences of which are just
enabled" means a general, clearly defined procedure or design beginning to be understood. There are a multitude of costs
with options so it can be modified to fit local situations. for wildlife associated with roads, from direct effects such
Currently it is difficult to link ecological values with safety values as collision-caused mortality and habitat fragmentation to
of wildlife mitigation measures for roads. Standardized proce- indirect effects such as decreased reproductive success and
dures need to be developed for combining the estimated mon- road avoidance. There are data that suggest the barrier
etary costs of proposed wildlife crossings with ecological, safety, effects of the roaded landscape reduce permeability of those
regulatory streamlining, and amortized monetary benefits. areas for wildlife populations. Several studies have demon-
Standardized procedures would allow state and provincial strated that roads may act as barriers to small-mammal
departments and ministries of transportation to better evaluate movements186,12,153 and as filter-barriers to large-mammal
how, what, and where to establish mitigation measures for movements.23,105 Roads can be complete barriers to indi-
wildlife in developing transportation programs and projects. viduals who cannot make their way across and whose road-
related mortality can affect their small populations. This is
Priority. Develop standardized procedures for estimating especially true for populations of wide-ranging carnivores
monetary costs and ecological, safety, regulatory streamlining, who are particularly vulnerable to road traffic collisions
and amortized monetary benefits. Researchers in ecological (Florida panther [Puma concolor coryi],155 ocelot [Leopardus
fields need to work with economic researchers to better esti- pardalis],118 puma [Puma concolor],18 Iberian lynx [Lynx
mate the economic benefits of wildlife, intact ecosystems, and pardalis], 87 and wolves [Canis lupus]101). These effects over
ecological processes. These values, once standardized in some time will cause wildlife populations to suffer reduced sizes,
manner, could then become part of cost-benefit analyses of isolation, skewed sex ratios (turtles222), depleted gene
mitigation measures. These analyses also need to include the pools, and even extirpation. Indeed, concern has been
amortized monetary benefits to society of reduced wildlife raised regarding the influence of highways on normal
roadkill and vehicle collisions. These benefits would include mammalian distributional patterns and perhaps ultimately
reduced monetary costs to public agencies, insurance compa- on speciation.10
nies, medical and personal costs to motorists, and increased For all that is known, there are still tremendous gaps in the
wildlife populations available for recreational opportunities understanding of just how the genetics of populations are
such as hunting and bird watching. Taking into consideration being affected by the fragmenting and isolation effects of
the economic benefit of including wildlife crossings early in roads.197 The barrier effect of roads may reduce wildlife
project planning is necessary, for this approach can streamline movement to the point of isolation, thereby reducing gene
environmental regulatory processes, thereby reducing overall flow and increasing inbreeding and genetic drift.8,242 Current
project cost. Once these monetary benefits of mitigation literature supports such theories that roads are causing
measures are justified and standardized, a more realistic rep- genetic consequences for a variety of species. These species
resentative cost-benefit analysis method could be developed include wide-ranging grizzly bears (Urus artos)189,254 and
and employed across regions. black bears (Ursus americanus)256,231 and smaller localized
species such as beetles,138 mice and shrews,170 voles,103
Priority. Develop innovative and economically viable and frogs255. These and other studies indicate that research
"option-enabled" alternative crossing designs after conducting into the effects of genetic isolation due to transportation
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corridors is necessary to begin understanding the conse- mammals (but see Clevenger and Waltho55,58), gallinaceous
quences of roads and to mitigate their effects. birds (turkey, pheasant, and grouse: for sage grouse see Lyon
and Anderson151 and Connelly et al.60), and invertebrates
Priority. Continue to study the genetic consequences (insects, spiders, worms) and for dispersing plants. Future
of roads on wildlife. This research may most prudently be options may be limited if the implications of roads on the
focused on wide-ranging species, small-movement species, survivorship of localized and low vagility species (e.g., mar-
isolated populations, carnivores, amphibians, reptiles, and mots, bighorn sheep, and pikas) are not addressed. Gender
small mammals. Directed research efforts into the restriction responses to roads and crossings represent an unknown area
of movement and its genetic effects would help define the of knowledge. These issues are only some of the many that
needs for freedom of movement for the target species. Elimi- need to be addressed.
nation of barriers to movement is essential for individual Another area of importance addresses the impacts of the
reproductive fitness and survivorship and has population con- noise of roadways and how it affects local and wide-ranging
sequences. Genetic research will help to define these move- species, such as bears and neotropical migrants. Provocative
ment needs, the necessary road crossing rates, and potential work suggests that noise as indexed by volume and frequency
for appropriately designed wildlife crossings to help continue has important negative effects on decreasing the bird species
this flow. The research team argues that research will demon- richness and diversity.199 The research team added a research
strate that maintaining permeability of the landscape for a component that addressed the road noise issue to the small-
multitude of species will help negate the impacts of roads. mammal research for this project.
There is a need for long- and short-term research tar- Priority. Continue research that addresses the reactions
geted at assemblages of species to ascertain their reactions and adaptations of wildlife to roads and wildlife crossings.
and behavioral adaptations over time to roads and associ- Research that examines the assemblages of species reactions to
ated mitigation features. This research will inform the de- roads and crossings would be the most productive in relation to
velopment of "option-enabled" general crossing designs creating effective mitigation measures that allow the full range
that accommodate a wide range of species' requirements. of wildlife species to move across and underneath transporta-
There is an urgent need for knowledge that would help in tion corridors. Understanding the variables that contribute to
the design of wildlife crossings that allow the full range of wildlife behavioral reactions and how they may change over
wildlife species to move across and underneath transportation time is important. As transportation and natural resource pro-
corridors. Information concerning behavioral reactions to fessionals strive to create effective crossings that wildlife adapt
roads and adaptations to crossings is lacking for most indi- to and actually use, consideration of extending monitoring
vidual species, but particularly for species' reactions in an efforts of crossings over several years in order to document the
associated community.58 For instance, even though mitiga- range of habituation and adaptation periods will be most
tion measures may be designed for specific wide-ranging and beneficial. These efforts will be different among species and
fragmentation-sensitive species (e.g., grizzly bear and lynx places. This priority can be addressed through specific regional
[Lynx canadensis]), there still are not sufficient design data to wildliferoad research and also species-specific studies that may
develop crossing structure guidelines for many of these be broadened to include these objectives. Within each region of
species,79,56,58 much less suites of other species associated with the country, the local scientists and wildlife and land managers
the target species. Prior to developing guidelines for appro- are the professionals who can best address these questions,
priate mitigation measures, a better understanding of roads because wildlife reactions to roads and crossings vary from place
effects on suites of species is most desirable. To date there are to place. A crossing structure type that works for one popula-
relatively few studies of population-level and/or assemblage- tion in a specific place may need to be modified to work
level effects of roads. The existing studies suggest that the effectively with another population and place. Regional
impacts can be significant. Findlay and Houlahan90 found sig- research that addresses the effects of roads and their associated
nificant effects of road density on species richness of wetland development, traffic, and noise on assemblages of species and
amphibians and reptiles, birds, and vascular plants. Fahrig et those species reactions to mitigation measures would greatly
al.81 and Vos and Chardon238 found that presence/absence as contribute to creating effective mitigation measures that allow
well as density of local amphibian populations can be affected associated wildlife communities continued movement.
by road traffic. Forman et al.97 found decreased avian distri-
bution and breeding near roadways in direct proportion to The effects of roads and crossings on ecosystem relation-
the volume of traffic on those roads. ships are largely unknown and need to be better assessed
There are several groups of species for which there is a and understood.
paucity of research and whose needs have not been ade- Road effects on ecosystems and landscapes need to be
quately addressed. Work is limited for carnivores and small studied and quantified. Wildlife crossing mitigation measures
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also need to be studied to assess their impact on ecosystems. critical road density. This is an area in which research is ur-
Landscapes and ecosystems are affected by roads and other gently needed. Other ecosystem components affected by
transportation structures synergistically with other human roads could also be measured with road density, including
infrastructure, changed ecosystem processes, and changed peak flows in mountain streams98, erosion, and the spread of
wildlife and plant populations. The most obvious change to invasive plants and the subsequent impacts for ecosystem in-
ecosystems is fragmentation. Fragmentation is a more diffi- tegrity, to name a few.
cult phenomenon to evaluate than direct effects on specific Road density is a simple measure, but road impacts on
species, and is analyzed over larger areas and greater time ecosystems vary considerably with traffic volume, speed, and
scales than most ecological studies. Forman et al.96,98 suggest infrastructure width, surface, and design.129 For example,
using road density as a measure of fragmentation caused by Foreman and et al.97 found grassland birds avoided regular
roads. Road density is a simple spatial measure, providing an breeding in patch edges near roads in direct proportion to
overview of the landscape.98 Other types of fragmentation road volume, moving breeding activities farther away (up to
measures could also be used to evaluate roaded landscapes. 1 km away) from roads with greater vehicle numbers per day.
Further evaluation is also needed to understand how roads In order to gain a more thorough understanding of such road
and mitigation measures influence and alter natural processes effects, the research team suggests examining the properties
such as the flow of water, ecosystem dynamics (e.g., the rela- of the roads in conjunction with density to ascertain the eco-
tionships between ungulates and their habitats), species logical relevance of each road.115
interactions (e.g., predator-prey dynamics, see Little et al.149), Other aspects of the roaded landscape could be analyzed for
population movement (e.g., movement to breeding areas), impacts to ecosystem function. Analyzing the specific form or
and individual behavior (e.g., the avoidance of roads by spatial pattern of the network of remaining natural patches
mothers with young, for grizzly bear see Proctor et al.189). and roads could reveal ecosystem properties.98 This could be
Ecological effects are often indirect and multicausal and accomplished in part through the use of indices of patch size
cannot be measured as easily as counting roadkill carcasses. or mesh size.132 Different mesh/patch sizes of natural areas
This is in part the reason why relatively little is known about contribute to different ecological conditions.98 With such in-
the effects of roads on ecosystem processes. Clearly, there is a dices, studies could be compared and contrasted to evaluate
need for a comprehensive synthesis that documents the indi- how roads are affecting ecosystem function and the basic eco-
rect effects of roads on ecosystems and how these cumulative logical processes such as water flow, disturbance regimes,
effects may in turn influence landscape permeability. predator-prey interactions, seed dispersal, and movement
among populations. These effects could be summed over
ecosystems to find the cumulative costs of roads over regions.
Priority. Understand the effects of road density on the
landscape for species of concern and ecosystems in general.
For many species, roads generally reduce population sizes Priority. Measure the effects of wildlife mitigation meas-
and increase the risk of population extinction. However, ures on ecosystem dynamics. These assessments could be
most species populations can persist in the presence of at least performed by monitoring specifically chosen ecological
some roads. Therefore, in the context of road impacts on indicators at different levels of biological organization: genes,
wildlife, probably the most important and most difficult individuals, populations, and species across landscapes.
question to answer is: what is the critical density of roads in Assessments would be performed both before and after place-
an area below which a population of interest can not persist? ment in order to judge the effectiveness of actions aimed at
This question is not easy to answer because of the spatial and connecting communities and populations and possible cumu-
temporal complexities of road impacts. As road density in- lative effects.58 Ecosystem assessments using specific ecological
creases, wildlife habitat becomes increasingly fragmented.132 indicators would benefit from standardization and accuracy
The numerical responses of large mammals to roads are gen- testing in order to obtain a tangible conservation value of the
erally interpreted as responses to a road density threshold. studied crossing structure. That would allow assessment of the
Road densities above the threshold significantly reduce the ecological value of mitigation measures and possible cost-
probability for sustainable populations and coexistence. benefit values of potential crossings. Examples of questions to
Several models have been developed to predict wolf pack oc- be answered include but are not limited to: How does the
currence or survival in relation to road density in Minnesota wildlife crossing structure affect the predator-prey dynamics
and Wisconsin.230,166,171,172 A road density threshold of 0.45 within an ecosystem? Does the presence of artificially increased
km/km2 was identified that best classified pack and non-pack vegetative cover near passages change the use of these areas by
areas for wolves.171 Similar road density thresholds were cover-associated species? How does placement of a crossing
reported for pumas and brown bears.237,54 However, these structure influence the willingness of target species to use it?
studies only scratch the surface of the problem of estimating For instance, if a structure is placed along a riparian area does
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it promote the passage of some species and individuals while efforts. A likely partnership for connectivity analyses fund-
hampering the movements of others? The accomplishment of ing could include states DOTs and provincial MoTs and
the priorities in this task will take the concerted effort of many their wildlife agency counterparts who can benefit greatly
scientists. from such analyses. This type of effort has worked in several
states. Regional approaches may work best. An effective type
The larger-scale landscape context of road effects and of analysis might include GIS models that analyze landscape
transportation programs needs to be addressed through con- linkages based on four important variables: focal species
nectivity analyses at the state/provincial and regional levels. movement patterns, land cover, human density, and road
There is a need for all states and provinces to conduct density,212 or a more inclusive list of environmental vari-
state/province-wide connectivity analyses to help determine ables.215 Digital topographic data can also help identify
"fracture zones" among conservation areas that can then be movement corridors in places containing drainages and
prioritized in transportation programs for mitigation efforts. ridgelines. Finally, the collective knowledge of land man-
These fracture zones are where transportation corridors agers, wildlife biologists, non-profit environmental organi-
bisect natural wildlife movement corridors and potentially zations, and state DOT/provincial MoT professionals can be
restrict movement and permeability of the natural world. brought together in critical connectivity workshops where
There appear to be few large-scale state- or province-wide the participants can work synergistically to identify key land-
landscape approach efforts to address the effects of the scape linkages and the transportation corridors that frag-
roaded landscape on wildlife and ecosystems. Although the ment them, and prioritize projects needed to restore wildlife
concept of "context-sensitive planning" is gaining national and ecosystem permeability. In light of the amount of
attention within the transportation community, it does not progress that has been made in these workshops in the past
appear to the research team to explicitly include the 2 years,69,204,203,205 this priority holds great promise.
surrounding wildlife habitat. The research team believes
connectivity analyses create a window of opportunity to A continent-wide set of guidelines is needed for defining
include ecosystem-level and landscape-scale considerations specifics in the consideration, placement, design, mainte-
in transportation programs and individual projects. Without nance, and monitoring of crossings and other mitigation
a proactive approach, future measures aimed at patchwork measures.
retrofitting and restoration may remain a poor second There is a need for research to aid in the development of
choice to properly planned and maintained landscape guidelines to facilitate the planning, placement, design,
permeability in most regions. maintenance, and monitoring of wildlife crossings across
Currently, landscape-scale connectivity analyses have been North America. Transportation planners, engineers, and bi-
conducted in a variety of formats in several states and ologists need guides to effectively mitigate for the effects of
provinces, including California,187 Washington,212 Montana,205 roads on all wildlife species within affected communities.
Colorado, Utah, Arizona, New Mexico, and eight southeastern Although wildlife crossings have been built for more than
states.46 These analyses involved landscape linkage models and three decades, there is no standardized set of guidelines to
the creation of GIS-generated maps, or workshops aimed at assist these professionals and other agency personnel to mit-
addressing statewide connectivity, or rapid assessment work- igate for terrestrial and aquatic wildlife.11 A North American
shops centered on specific roads, where professionals from set of guidelines for wildlife crossings would include
across the state met to identify and map all potential major specifics on conditions that trigger the consideration of mit-
landscape linkages within the state and the roadways that po- igation measures; how and when to plan for structures;
tentially fracture these connections. The research team suggests where to locate mitigation measures; design considerations;
that similar efforts be conducted for all states and provinces how to combine several types of efforts such as fences,
and the results incorporated into spatially explicit statewide underpasses, and ROW escape structures; standards for
databases and programs so these maps and accompanying monitoring and maintaining structures; and how to meas-
data can be used in DOT and MoT planning for linking ure the success of projects.
mitigation and implementing changes in their long-range
programs.80 Priority. Define the necessary conditions for considering
when to identify areas in need of wildlife crossing mitigation
Priority. Researchers, agency personnel, non-profit measures. Predictive models or threshold requirements would
organizations, and the public together can create and dis- help determine when (a) crossing structure(s) is (are) needed
seminate state- and province-wide connectivity analyses. to help mitigate for certain volumes of traffic, safety consider-
The research team suggests collaboration in conducting the ations, roadkill hotspots, the presence of endangered, threat-
science, widely attended workshops to enhance needed ened species or species of special concern, landscape linkages
information exchange, and partnerships to fund these fracture zones created by transportation corridors, and
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the presence and need for movement of surrounding wildlife seldom if ever been monitored, or have been only sporadi-
populations throughout critical habitat. cally checked to determine if they have served their
purpose.111 Guidance on monitoring efforts and temporal
Priority. Engage the research community in the devel- specifications would greatly assist managers, planners, and
opment of guidelines for the placement of crossings. Scien- biologists and allow for comparable analyses among struc-
tists and wildlife managers and biologists need to critically tures to ascertain their efficacy. The majority of past and
review the habitat-based linkage or movement models and current monitoring projects have been conducted in concert
rapid assessment techniques currently used to identify with academic institutions and the U.S. Fish and Wildlife
passage placement, and identify a suite of possible methods Service. This monitoring, if done correctly, is essentially
for practitioners. Emphasis should be on criteria to locate research. Future monitoring research could be standardized,
mitigation measures.111 implemented by, and mandated for future projects by the
state wildlife and transportation agencies and federal
Priority. Design considerations need to be adequately ad- agencies, including resource-based agencies such as the U.S.
dressed for the full suite of crossings. There is a need for Fish and Wildlife Service, Environment Canada, Fisheries
research to help in the selection of target species, and the de- and Oceans Canada, and transportation entities, for example
termination of the number, size, and dimensional character- the FHWA and Transport Canada. The overall standardiza-
istics of structures needed within an area to help maintain tion of monitoring projects would mean a commitment of
maximum permeability for the suite of associated species.80 necessary funds from U.S. Federal Highways Program and
Design guidelines for mitigation measures associated with other sources. The expected benefit would be an enhanced
crossings are also needed. Considerations include determin- understanding of which structures work most effectively in
ing the required lengths of fences erected to guide wildlife specific situations.
(both large and small) to crossings; addressing the suitability
of establishing or eliminating median islands in conjunction Priority. North American guidelines for crossings need
with crossing areas; creating underpasses with a naturally lit to include methods for defining success and effectiveness.11
open space in the median of divided highways, in effect creat- Defining success would involve addressing the number of
ing two underpasses under travel lanes rather than one long individuals (including the difference between males and
darker underpass; taking into account other nearby trans- females and juveniles and adults) of a target species who have
portation corridors such as railways; retrofitting existing used a structure, number of species found to use a structure,
culverts for fish and other aquatic species; and possible use by endangered and other high-needs species, reduction of
alternatives or complements to crossings such as remotely wildlifevehicle collisions, as well as other measures. Fish pas-
sensed, active lighted warning signs, possible crosswalks over sages created in retrofitted and replaced culverts and bridges
low-volume roads, the clearing of vegetation, temporary clo- along streams have been evaluated through a quantifiable
sure of roads, public transit options, reduced-speed zones, and checklist of goals accomplished: e.g., the number of a certain
the elimination of certain roads (road decommission). Indeed species using the new passage, the number of kilometers those
several measures may be coupled for maximum effectiveness. species have traveled upstream, how many individuals breed
and re-populate a specified river distance within a watershed.
Priority. Monitoring standards for crossings need to be These kinds of quantifiable measures present an objective
researched and created. Bank et al.11 suggest a national U.S. method for assessing wildlifelandscape permeability across
policy requiring post-construction monitoring and mainte- roadways and would greatly improve the credibility of
nance measures for wildlife. Most existing structures have wildlife crossings science and practice.
