Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsSome links on this page are affiliate links: if you buy through them we may earn a commission, at no extra cost to you.
A wildlife crossing succeeds only when it reconnects usable habitat, guides animals safely to the structure, and remains functional after construction. The bridge, tunnel, or culvert is one element of a larger system that includes landscape planning, fencing, drainage, approach habitat, revegetation, maintenance, and monitoring.
This guide explains how to scope and design that system. Highway crossings are engineered public infrastructure, not do-it-yourself projects: qualified wildlife biologists, transportation planners, civil and structural engineers, revegetation specialists, and land managers must establish dimensions, loads, drainage, safety measures, permits, and construction details for the actual site.
As an Amazon Associate I earn from qualifying purchases.
What a wildlife crossing is—and what it is not
A wildlife crossing is a planned route that allows animals to pass over, under, or sometimes across a transportation barrier while maintaining habitat connectivity and reducing roadway conflict. Common forms include landscape bridges, wildlife overpasses, underpasses, culverts, amphibian and reptile tunnels, and canopy crossings.
There is no universal crossing design. The appropriate form depends on the focal species, movement behavior, habitat on both sides of the road, terrain, soils, water, road geometry, human disturbance, available right-of-way, and long-term land-use plans. The Federal Highway Administration (FHWA) Wildlife Crossing Structure Handbook: Design and Evaluation in North America (2011) presents 11 over-grade and below-grade crossing types. It is a technical reference, not a binding national specification or a construction drawing set.
Popular on Amazon
- Valued Carpenter Pencil Set: You will get 2 pcs solid carpenter pencils with 26 piece 2.8 mm refills, 1 replaceable sharpener, 1 plastic storage box.The complete carpenter pencils combination allows you to finish your work faster and more easily
- Deep Hole Marker Pencil: The deep-hole construction pencils adopts 45mm elongated tip design, which is more convenient to mark in the small hole or in other tight areas that other carpenter markers cannot reach
- Carpenter Pencils with Sharpener: The sharpener is screwed into the top of the work pencil, which won't get lost either. Built-in pencil sharpener that keep the lead with pointed and smooth to Improves line of sight in fine work
- Stronger Solid Lead: This work pencil is matched with a 2.8 mm thick lead , which is much thicker and stronger during the drawing process of construction work, it will not break or damage easily
- Marks on Various Surfaces: 3 colors solid construction pencil can marks on various surfaces,such as metal, plastic, wood, paper etc. Ideals for woodworkers, contractors, craftsmen, builders, merchants and masons
FHWA’s current Wildlife Crossings Program supports projects that reduce wildlife-vehicle collisions and improve terrestrial and aquatic connectivity. Its design standards and a handbook update were still listed as work in development on the agency’s Wildlife Crossings Program Activities page last updated October 20, 2025. Treat the 2011 handbook as established general guidance and verify current federal, state, provincial, tribal, and local requirements before design.
Start with the ecological and safety problem
Before choosing a bridge or tunnel, define what the project must accomplish. A crossing may be intended to reconnect a migration route, preserve access to seasonal habitat, reduce collisions with large mammals, protect amphibians moving to breeding ponds, or maintain an arboreal route through a road corridor. Each objective produces different siting and design requirements.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Define focal species and performance objectives
List the species or species groups the project is meant to serve. Large mammals, small mammals, reptiles, amphibians, bats, and tree-dwelling animals differ in body size, cover requirements, approach behavior, tolerance of noise and light, and willingness to use an unfamiliar structure. Identify whether the objective is passage by a single priority species, a guild of species, or broader habitat connectivity.
Write measurable objectives before selecting a structure. Examples include maintaining access between two protected habitat blocks, reducing animal entry onto a roadway, providing a dry route during normal flows, or retaining a seasonal movement connection. A monitoring plan can then test whether those objectives were met.
Assemble the available evidence
Use several evidence streams rather than relying on a single carcass cluster or anecdotal sighting:
- Wildlife-vehicle collision and carcass records, with dates, locations, direction of travel, and species identification where available.
- Track, camera, telemetry, genetic, road-crossing, or field-observation records that indicate movement routes.
- Habitat maps, protected-area boundaries, wetlands, streams, ridgelines, seasonal ranges, and known breeding or denning areas.
- Current and proposed development, forestry, agriculture, recreation, utility corridors, and other land-use changes that could redirect movement.
- Road geometry, traffic volume and speed, drainage, lighting, barriers, medians, and crash patterns.
FHWA’s current program materials describe crash records, carcass records, and animal identification as data categories in a collision and carcass methodology under development. They also describe mitigation-threshold guidance as under development. Use those materials to understand the direction of federal work, not as final universal thresholds.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallCrashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteChoose the site at two scales
The best location is not necessarily the point with the most carcasses. It is the location where a structure can reconnect habitat and remain approachable, safe, and usable over its design life.
Site-scale assessment
Survey the immediate road corridor and both approaches. Record:
- Existing and likely future land use beside each entrance.
- Terrain, road cuts, valley alignments, slopes, rock, soil depth, and constructability.
- Streams, wetlands, flood pathways, groundwater, seasonal inundation, and drainage outfalls.
- Available right-of-way and space for ramps, wing fencing, gates, maintenance access, and staging.
- Road lanes, shoulders, medians, embankments, sight distance, lighting, noise, and nearby intersections.
- Human activity, trails, agricultural operations, buildings, pets, livestock, and recreation.
- Whether animals can reach each entrance without being funneled into the road or an adjacent development.
FHWA identifies compatibility of adjacent land use, both present and future, as the most important part of site selection. A structurally excellent crossing can fail if a new road, subdivision, bright lighting, frequent pedestrians, or intensive land management blocks the approach.
Landscape-scale assessment
Map the crossing within the larger movement network. Confirm that habitat remains connected on both sides and identify where animals would travel before reaching the road. A short structure cannot compensate for a severed corridor several hundred metres away, nor can a crossing remain effective if future development closes one entrance.
Recommended Free Tools
Look for protected lands, riparian corridors, ridgelines, wetlands, forest blocks, grasslands, and other features that provide continuity. Discuss conservation easements, public land management, zoning, and foreseeable changes with the agencies and landowners responsible for those areas. Include a land-management strategy in the project, not only a construction drawing.
Also popular on Amazon
- Ergonomically Designed: Work in tight areas with a compact design that gets into tough spots
- Both tools are designed to fit into difficult to reach spaces
- Complete a wide range of applications with a high-performance motor that delivers up to 300 UWO, and an impact driver delivering up to 1,400 in-lbs of torque
- Both the DEWALT impact driver and drill driver feature integrated LED work lights with a convenient 20-second delay, ensuring enhanced visibility in dimly lit or challenging work areas
- One-Handed Loading - Keep one hand free with a 1/4 in. hex chuck that accepts 1 in. bit tips
Rank candidate locations
Use a documented screening matrix so that ecological value is not overwhelmed by a single engineering convenience. A practical matrix can score each candidate against:
| Criterion | Questions to answer |
|---|---|
| Connectivity | Does the site link habitat or a documented movement route on both sides? |
| Target species | Will the location and approach conditions suit the focal species? |
| Land-use security | Can present and future adjacent land use preserve access? |
| Terrain and hydrology | Do slope, soil, stream, flood, and drainage conditions support the proposed form? |
| Road and public safety | Can the design avoid creating hazards for drivers, workers, and nearby users? |
| Constructability | Is there enough right-of-way for the structure, approaches, fencing, access, and staging? |
| Long-term management | Can fencing, vegetation, drainage, gates, and monitoring be maintained? |
FHWA describes connectivity potential as high, moderate, or low and cautions against mixed human use in high-potential areas. Use that as a planning concept, then apply local wildlife data and current agency criteria.
Select the crossing type for the species and site
Do not reduce the decision to “overpass versus tunnel.” FHWA’s handbook includes landscape bridges, wildlife overpasses, multi-use overpasses, canopy crossings, and amphibian or reptile tunnels among 11 types. The following comparison shows the decision logic; it is not a substitute for species-specific design.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →| Crossing form | Typically considered when | Important cautions |
|---|---|---|
| Landscape bridge | A broad, habitat-like connection is needed across a major road, cut, or valley. | Requires substantial structural capacity, soil depth, drainage, approach land, and long-term vegetation management. |
| Wildlife overpass | Terrestrial animals need a separated route above a road and a wide, wildlife-only corridor is feasible. | Noise, light, fencing, edge treatment, soil, and approach cover strongly influence use. |
| Multi-use overpass | People and wildlife must share a crossing where compatible use can be demonstrated. | Human activity can reduce use by sensitive species; FHWA recommends wildlife-only treatment in high-connectivity settings. |
| Underpass or wildlife tunnel | Road elevation, a cut, embankment, or terrain makes a below-grade route practical. | Light, openness, flooding, drainage, length, and interior visibility can determine whether animals enter. |
| Amphibian or reptile tunnel | Small, low-moving species need to cross between breeding and terrestrial habitat. | Fine-mesh guidance fencing, moisture, drainage, and very precise alignment are essential. |
| Canopy crossing | Arboreal species need continuity between tree crowns across a road. | Attachment, span, wind, maintenance access, and connected canopy on both sides must be engineered. |
Compare alternatives on target species, habitat continuity, topography, hydrology, construction constraints, human disturbance, maintenance access, and the ability to protect the approaches. A cheaper or shorter structure is not a successful mitigation measure if animals cannot find or tolerate it.
Develop the engineering concept before choosing materials
Site investigations should precede final dimensions. Geotechnical work, hydrologic analysis, traffic and structural engineering, utility coordination, and ecological design need to proceed together. FHWA notes that crossing choices affect both project budgets and public safety.
Use published dimensions as qualified starting points
The following figures are examples and general guidelines from FHWA’s 2011 handbook, not universal specifications:
| Published figure | How to interpret it |
|---|---|
| 8–12 ft (2.4–3.6 m) trees | Example landscape-bridge design detail; actual tree size depends on structure, soil, species, wind, and establishment conditions. |
| 2–3% drainage slope | Example landscape-bridge detail; final drainage must reflect rainfall, soil, surfacing, and outlet conditions. |
| 5–8 ft (1.5–2.4 m) soil depth | General wildlife-overpass guideline; required depth varies with the vegetation, root systems, structural loads, and water regime. |
| Minimum 130–165 ft (40–50 m) overpass width | Handbook general guideline for the referenced overpass design, not a universal minimum for every species or location. |
| Recommended 165–230 ft (50–70 m) overpass width | Handbook general recommendation for the referenced design; confirm with focal-species behavior and site constraints. |
| 8 ft (2.4 m) fence or berm height | Appendix guideline for the referenced overpass design; fence height and details must be checked against species and approach conditions. |
The handbook also discusses a 75–80-year lifespan comparison for bridge structures. That is a long-lived infrastructure planning context, not a guarantee for a particular crossing, its vegetation, fencing, drainage, or other components.
Free tools Windows power users keep installed
One-click scans. No signup required.
Choose structural materials by function
FHWA’s appendix gives examples of steel truss or concrete bridge spans. Landscape-bridge arch options include prefabricated or cast-in-place concrete and corrugated steel. The final choice depends on span, loads, soil, construction access, corrosion exposure, local practice, and inspection requirements.
Separate the structural specification from the habitat specification. A structurally adequate deck may still be unsuitable if it lacks soil, drainage, cover, quiet edges, or a safe connection to the surrounding habitat.
Preserve soil and build habitat structure
Where feasible, maximize continuity of native soils and avoid importing soils from outside the project area onto wildlife overpasses. Imported material can differ in texture, chemistry, seed bank, pathogens, and water-holding behavior. Soil sources, amendments, erosion controls, and handling procedures should be approved by the project ecologist and engineer.
Logs, root wads, rock piles, brush, and woody debris can provide refuge and microhabitat for smaller or cover-associated fauna. Place these features so they remain stable, do not obstruct drainage or maintenance, and create useful stepping-stone cover rather than random clutter. In arid settings, FHWA mentions additional woody debris and rocks as useful habitat features.
Also popular on Amazon
- 【Great Compatibility】This Katerk 1/4 inch hex shank bit holder is specifically designed for 1/4 inch hex shank drill bits. It's compatible with most 1/4 fast hex handles, hex sockets, various electric screwdrivers, and handheld screwdrivers. The bit holder makes it a valuable addition for any handyman.
- 【Secure and Safe】Built with a secure backup nut design, each drill bit holder securely locks onto your bits, ensuring they stay firmly in place. Additionally, our bit holder incorporates a high-quality steel ball rolling design that holds up to several kilograms of weight, ensuring your various drill bits don't fall off.
- 【Easy One-Handed Operation】The bit holder for impact driver allows you to change bits single-handedly, simplifying your workflow. Its multi-color design further allows for quick identification of the drill bit you need.
- 【Compact and Convenient】Thanks to its compact size, this 1/4 inch bit holder is easy to carry around. The bit holder allows for easy attachment to various tools, making this a convenient addition to your construction accessories. The Katerk bit holder is cast from high-quality alloy material, promising a long product lifespan. Despite its rugged strength, the bit holder remains lightweight, making it portable.
- 【Cool Christmas Gift For Men Stocking Stuffers】 This screwdriver bit holder, driver bit holder, impact bit holder, can be given as a gift to your loved one, especially for anyone involved in construction or electrical work. It's a must-have for stocking stuffers for men and women, tools gifts for dad, tech gadgets for men, gifts for dad, gifts for him, gifts for husband, gifts for boyfriend, cool gadgets for men, and cool gifts for dad.
Design fencing, gates, and approaches as part of the crossing
Animals must be directed toward a usable entrance and prevented from entering the roadway beside it. Fencing is therefore part of the mitigation system, not an optional accessory.
Connect fencing to the landscape
Extend exclusion or guidance fencing far enough to intercept likely travel routes and tie it securely into the structure. Avoid gaps at abutments, drainage outlets, maintenance gates, property lines, and changes in elevation. Provide gates and access points where maintenance, emergency response, or land management requires them, while preventing routine wildlife escape onto the road.
Do not copy one fence height, mesh, buried skirt, or gate detail to every project. Large mammals, small mammals, reptiles, and amphibians can require different mesh sizes, buried edges, overhangs, escape features, and inspection intervals. The 8 ft figure cited above applies only as a handbook guideline for a referenced overpass design.
Make the approach inviting and quiet
Approach habitat should resemble the connected habitat and provide cover where the focal species expects it. Remove or manage attractants that draw animals toward the road rather than the crossing. Roads, bright lighting, frequent pedestrians, machinery, pets, and exposed open ground near an entrance can discourage use.
Keep a clear maintenance route without turning the entrance into a human gathering space. In high-connectivity locations, wildlife-only use is generally preferable to shared recreation unless monitoring and local evidence show that shared use is compatible.
Plan planting to imitate the habitat being connected
Planting is not decorative landscaping. It should recreate the structure, cover, food resources, and seasonal cues that animals encounter in the habitat on either side.
Use local ecological references
FHWA recommends plant species that match, or are taxonomically close to, adjacent vegetation. Select climate-appropriate hardy or drought-tolerant species where conditions demand them, but do not substitute a generic “native mix” for a site assessment. Species, provenance, soils, moisture, elevation, fire regime, and target wildlife all affect the planting palette.
FHWA’s roadside revegetation guidance recommends involving revegetation expertise early in road and bridge or culvert replacement planning. Native forbs and grasses may be selected for food and browse, but the final mix must be specific to the location and ecological objective.
Arrange vegetation by function
For an example overpass layout, FHWA suggests:
- Trees and dense shrubs along edges to provide cover, refuge, and visual screening.
- Lower or herbaceous vegetation in more open central areas.
- Shrub piles, logs, woody debris, and rocks as interim or permanent refuge features, especially while plants establish.
This arrangement is not a universal template. Some species prefer open sightlines; others need continuous cover. Match the pattern to the focal species and adjacent habitat, then confirm that root systems, mature canopy, irrigation or establishment watering, fire risk, and maintenance access are compatible with the structure.
Specify soil, water, and establishment measures
Planting success depends on the soil profile and water regime as much as on the species list. Confirm soil depth, compaction, organic matter, infiltration, erosion protection, drainage outlets, and expected drought or flood periods. The example landscape-bridge guidance calls for enough soil to support trees, retain water, and drain excess water.
Use erosion-control measures that do not create entanglement or chemical hazards for wildlife. Establishment watering, weed control, replacement planting, and protection from browsing may be needed during the first seasons. Define who performs that work and how success will be judged before construction begins.
Also popular on Amazon
- Long Nib and Deep Hole Marker: Our mechanical carpenter pencil with 45mm nib is designed for easy marking of deep holes or narrow areas. These construction pencils are the great choice for woodworking tools, construction tools, carpenter tools, contractor tools, wood carpentry tools and architect tools
- Extra Refills in 2 Colors for Versatile Marking: The construction mechanical pencil comes with 12 extra 2.8mm refills, including 6 red and 6 black refills. The black refill is suitable for light surfaces, while the red wax is perfect for dark surfaces. Our carpenter mechanical pencil makes sure that you'll have an ample supply for extended use
- Built-in Sharpener: Our construction pencil comes with a built-in sharpener to ensure the mechanical pencil tip is always sharp and ready for use. Never buy an extra pencil sharpener again. A great tool for any woodworker pencil, contractor pencils. The refill can easily be extended or retracted with a simple click of the pencils mechanical, allowing you to work more efficiently and accurately
- Portable Clip Design: Our deep hole construction pencil features a portable clip design, easy to carry and attach to your pocket or tool box, so that you can keep the carpenter pencils mechanical close at hand, making it a convenient tool to have on the go. Great gifts choice for carpenters
- Stronger Pencil Lead: The black refills are made of lead, sturdy and smooth. The red refills are made of wax, clear and light. These marking pencils are much thicker and stronger than normal pencils during the marking process of construction work, suitable for various surfaces, such as glasses, metal, boards, floors, walls, furniture, etc. The written marks can be easily wiped with a wet paper towel when needed
Build in a coordinated sequence
A crossing project is easier to control when ecological, roadway, structural, drainage, and revegetation decisions are made together.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →- Confirm the problem and objectives. Identify focal species, movement barriers, safety goals, connectivity goals, and intended monitoring outcomes.
- Survey the landscape. Map habitat, movement evidence, protected areas, current and future land use, hydrology, terrain, and road conditions at site and regional scales.
- Screen candidate sites. Rank connectivity, land-use security, constructability, safety, and long-term management, then document why the selected location is preferred.
- Compare crossing forms. Evaluate over-grade, below-grade, canopy, and small-animal options against species behavior, terrain, water, human disturbance, and available land.
- Complete investigations. Obtain geotechnical, hydrologic, structural, traffic, utility, and ecological information before fixing dimensions or materials.
- Design the complete system. Detail the structure, soil, drainage, habitat features, fencing, gates, approaches, access control, erosion protection, and safety measures as one package.
- Prepare the planting and maintenance plan. Specify locally appropriate plants, provenance, soil handling, establishment care, replacement criteria, invasive-plant control, and responsibilities.
- Construct with ecological controls. Protect retained habitat, prevent avoidable disturbance, maintain drainage, control sediment, and install fencing so animals are not routed into active traffic.
- Establish vegetation and habitat features. Place soil, logs, rocks, woody debris, shrubs, trees, and lower vegetation according to the approved habitat design, then protect the site while plants establish.
- Monitor and adapt. Track use by target species, fence breaches, road incursions, mortality, vegetation condition, drainage, erosion, and human disturbance. Correct problems rather than treating construction completion as project success.
Monitor performance and maintain the system
Monitoring should answer whether animals find the crossing, use it safely, and retain access over time. Set the methods and schedule during design. Depending on the objective, monitoring may include wildlife cameras, track beds, vegetation surveys, fence inspections, road-mortality records, hydrology checks, and observations of human intrusion.
Inspect after major storms, flooding, wildfire, heavy snow, vehicle strikes, vandalism, and nearby land-use changes. Look for collapsed or buried fence sections, open gates, washouts, blocked drainage, invasive plants, dead trees, compacted soil, excessive bare ground, and new paths that lead toward the roadway.
FHWA’s handbook includes a monitoring and adaptive-management chapter because a crossing’s performance cannot be established by construction alone. Use monitoring results to repair fencing, alter vegetation, add cover, manage water, restrict human access, or revise maintenance practices. Keep records that allow performance to be compared with the original objectives.
Common failure modes and how to prevent them
A structure is placed at a convenient but disconnected location
Prevention: verify movement routes and habitat continuity at the landscape scale, then protect both approaches from future obstruction.
The crossing is built without its fencing system
Prevention: design fence alignment, gates, tie-ins, drainage transitions, and inspection access at the same time as the structure.
Planting uses a generic seed mix
Prevention: match species and provenance to adjacent vegetation, climate, soils, and target wildlife; involve a revegetation specialist early.
Drainage is treated as an afterthought
Prevention: model runoff, groundwater, floods, erosion, and outlets during design. Keep habitat features from blocking drainage.
Human use overwhelms a high-value wildlife corridor
Prevention: favor wildlife-only access where connectivity potential is high, control nearby lighting and trails, and test compatibility through monitoring.
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →Published dimensions are copied without checking the site
Prevention: treat handbook widths, soil depths, fence heights, slopes, and tree sizes as qualified guidance. Have the project team confirm dimensions for the species, structure, soil, terrain, and jurisdiction.
Who should be on the project team?
A credible project normally requires coordinated input from:
- A wildlife biologist or ecologist familiar with the focal species and regional habitat.
- A transportation agency or roadway engineer responsible for traffic, safety, and right-of-way constraints.
- A structural and civil engineer for loads, foundations, drainage, grading, and materials.
- A geotechnical and hydrologic specialist where soils, slopes, streams, or floods control feasibility.
- A revegetation or restoration specialist for soil handling, plant selection, establishment, and invasive-species control.
- Land managers and affected landowners who can preserve approaches and carry out long-term maintenance.
The FHWA handbook is aimed primarily at transportation, natural-resource, and land-management practitioners. It is useful for scoping conversations and design review, but it cannot replace site investigations, agency coordination, or stamped engineering documents where those are required.
Bottom line for planning a wildlife crossing
Build the habitat connection first in your reasoning, then the structure. Select a site where movement routes and future land use can remain secure; choose the crossing form for the focal species, terrain, and water; design fencing and approaches with the structure; use soils and plants that resemble the connected habitat; and fund maintenance and monitoring for the life of the project. The FHWA 2011 handbook supplies valuable North American guidance, but every dimension and planting decision must be verified for the actual landscape and current requirements.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallOutdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchQuick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
