Engineering and Design Terms related to Animal Crossings and Animal Barriers
American Association of State Highway and Transportation Officials.
A substructure supporting the end of a single span or the extreme end of a multiple span superstructure retaining or supporting an approach embankment.5 Also, the part of a structure (such as an arch or a bridge) that directly receives thrust or pressure.7
A grade separation structure designed to allow wildlife to cross over an intersecting highway or railroad. It is usually covered with vegetation. Also called ecoduct, green bridge, land bridge, biobridge, wildlife bridge or Animal overpass, landscape connectors, wildlife overpass, Wildlife Crossing Structure or wildlife overcrossing.10
Animals passage under vehicle traffic via a Bridge or Culvert.
A bridge forms part of the roadway and is usually more than 20 feet long. Can be single span or multiple span if it has piers.
concrete box culvert: A square or rectangular, “box” shaped culvert under a roadway. Can be cast-in-place or precast steel reinforced concrete.
structural plate culvert steel: structural plate consists of corrugated steel sections that are bolted together to form the required shape. The corrugated sections are commonly referred to as plates and have a standard corrugation profile of 6 x 2 inches that are formed perpendicular to the length of the culvert bridge. The plates are assembled into various shapes that include round, pipe arch, singles-radius arch, horizontal ellipse, low profile arch, high profile arch, pear, underpass and vertical ellipse and special shapes.9
deep corrugated buried bridge: The latest innovation in Soil Steel Bridges, Deep Corrugated Structural Plate is available in spans up to 80 ft and thicknesses from 0.140 to 0.314 inches. These bridge structures are ideal for grade separations or hydraulic applications. Two types of corrugation profiles are available, Type I deep corrugated structural plate has a 15 x 5 ½ inch corrugation and Type II deep corrugated structural plate has a 16 x 6 inch corrugation. Plates are assembled into various shapes, including, round, single-radius arch, multiple-radius arch, box culvert, and special shapes.9
Soil or rock placed behind and within the abutment and wingwalls to fill the unoccupied portion of a foundation excavation.2
The layer, or layers of material of designed thickness placed on a subbase or a subgrade to support a surface course.4
A support element transferring loads from superstructure to substructure while permitting limited movement capability. 5
In-roadway barrier, grid span, for various species of large deer and antelope including Red Stag and Kudu. Typically, 14’- 16’ in the driving distance. Used in Conjunction with Bison Guard Wings.
Buffalo Guard (see Bison Guard)
Cast in Place Concrete
The act of placing and curing concrete within formwork to construct a concrete element in its final position.5 Optional method of forming cattle guard bases.
In roadway barrier made of Linear rails or bars flush with the roadway surface built over an excavated pit, designed to prevent livestock from crossing but not people or vehicles
Also called Stock Grid, Fence Gap, Vehicle Pass, Auto Gate, Cattle Grid, Cattle Guard, Texas Gate, Stock Gap, Cattle Stop, Pit Gate, Car Crossing, Corduroy gate, Run-over, Mato Burro – (Brazil and Argentina), Guarda Ganado (Argentina) See Photo
Cattle Guard BasesSubstructure of a grid span
Used to transfer a vehicle load from the grid into the ground. Often referred to as Cattle Guard Footers, Sills or abutments. See Photo
Cattle Guard Gate Support Ring
Triangular support vertical attached to the side of a cattle guard, for mounting and support of a swinging gate. See Photo
Cattle Guard Cap (Type 1)
Trapezoidal Roll formed rail manufactured specifically for use on cattle guards. Has a wider base dimension than top dimension. 3” Wide Base x 3” Tall x 2” Wide Top. The 3x3x2 is the preferred rail for the BLM, USFS, FHWA, NRCS, Montana DOT, South Dakota DOT and more. Also known as Hat Channel, rolled rail, top cap, boss hog, critter stop. See Photo.
Cattle Guard Kit
All the parts required for a specific cattle guard assembly, packaged, to be welded by someone other than the manufacturer. Does not typically include paint systems. See Photo
Cattle Guard Specifications
Specific terminology used as part of a construction plan used to make sure that the owner gets the quality, load rating, paint type, arrangement, material grade etc. needed to perform as planned. See Example.
System to allow access to the middle portion of a cattle guard to clean between the rails, built up debris. Cleanouts are typically used where equipment will not be able to access after the project is complete and future maintenance will be manual. See diagram
The unobstructed space or distance between support elements of a bridge or bridge member.5
The static load imposed by the weight of the materials that make up a given structure.2
That portion of a bridge offering direct support for vehicular and pedestrian traffic.5
In-roadway barrier, grid span, for various species of deer including Black Tail Deer, Mule Deer and White Tail. Typically, 12’- 14’ in the driving distance.
Game Fence at least 8 feet posts are typically set t 8’ to 20’ intervals. Wire is brought tight to the ground
The load that is assumed for the design of a structure. It may include dead load (self-weight) , live load (vehicular load), snow load, wind load, earthquake load and all other lateral loads.
(AASHTO) Design Vehicle
A theoretical engineering vehicle wherein the weight, the number of axels, axel spacing, axel loads and live loads are displayed, an engineer can run calculations against to verify the AASHTO design criteria are met. With H Trucks and U Trucks, Pairs of axels (Tandems) are considered one axel load. Click Hyperlink to view design vehicles in further detail.
- H10 - 10 Tons Passenger Vehicle, Light Truck, Pickup, Tractor, Van Delivery Truck with a 4,000 lbs front axel load and 16,000 lb load on the back axel
- H15 - 15 Tons GVW A truck with a 6,000 lb front axel load and 24,000 lb load on the back tandem axel spaced at 4’ apart
- HS15 - 15 Tons GVW A truck with a 6,000 lb cab and a dual tandem axel load of 24,000 lbs spread between the two axles spaced at 4’ apart. Spacing between tandem axels 14’-30’
- H20 - 36 Tons GVW A truck with a 8,000 lbs cab and a single tandem axel load of 32,000 spread between the two axles spaced at 4’ apart. Spacing between Cab axel and Back axel 14’-30’
- HS20 - 36 Tons GVW A truck with a 10,000 lb cab and a dual tandem axel load of 32,000 lbs spread between the two axles spaced at 4’ apart. Spacing between tandem axels 14’-30’
- HL93 - 36 Tons GVW A truck with a 10,000 lb cab a and dual tandem axel load of 32,000 lbs spread between the two axles spaced at 4’ apart. Spacing between tandem axels 14’-30’. Also includes lane load of 640 plf per lane. Most up to date AASHTO LRFD standard highway vehicle.
- H25 - 25 Ton GVW A truck with a 10,000 lbs cab and a single tandem axel load of 40,000 spread between the two axles spaced at 4’ apart. Spacing between Cab axel and Back axel
- HS25 - 45 Tons GVW A truck with a 10,000 lb cab and a dual tandem axel load of 40,000 lbs spread between the two axles spaced at 4’ apart. Spacing between tandem axels 14’-30’
- HS30 - 54 Tons GVW A truck with 12,000 lb cab and a dual tandem axel load of 48,000 lbs spread between the two axles spaced at 4’ apart. Spacing between tandem axels 10’-26’
- U54 - 54 Tons GVW A truck with a 12,000 lb cab and dual tandem axel load of 48,000 lbs per tandem. The spacing between the two axels creating the tandem is 4.5’ apart. Spacing between tandem axels 14’-30’
- U80 - 80 Tons GVW A truck with a 12,000 lb cab and a dual tandem axel load of 74,000 lbs per tandem. The spacing between the two axels creating the tandem is 4.5’ apart. Spacing between tandem axels 14’-30’
- U102 - 102 Tons GVW A truck with a 8,000 lb cab and a dual tandem axel arrangement, the first tandem axel weighing 85,0000 lbs and the back tandem a 112,000 lbs. The spacing between the two axels creating the tandem is 4.5’ apart. Spacing between tandem axels 40’-48’
A fence or wall that funnels animals towards or away from a designated area. Examples are fences that funnel migrating deer towards an underpass allowing them to cross under a highway. Diversion fencing may also work to simply keep animals off the highway instead of diverting them to a crossing structure. Sometimes called a drift or guide fence.10
Abbreviation for a special category of wildlife and vehicle collisions describing collisions between deer and vehicle.10
Earthen return ramps
A type of one-way gate used in wildlife deterrent projects. These ramps allow the animal trapped in the undesirable area to escape by jumping off a one way ramp back to the area they are meant to be kept, also known as jump fence and slope jump. Often place in the corners of fenced in areas. 11 See Photo
In-roadway barrier, grid span, for various species of large deer and antelope including Moose, Red Stag and Kudu. Typically, 14’-16’ in the driving distance.
A structure (usually an escape ramp, funnel fence or one-way gate) designed to allow an animal trapped by a diversion fence to exit the roadway. They are designed to allow passage in only one direction so animals can escape the highway but have difficulty getting onto the highway.11
Factor of Safety
A factor or allowance predicated by common engineering practice upon the failure stress or stresses assumed to exist in a structure or a member or part thereof. Its purpose is to provide a margin in the strength, rigidity, deformation, and endurance of a structure or its component parts compensating for irregularities existing in structural materials and workmanship or other unevaluated conditions.2
The enlarged, lower portion of a substructure which distributes the structure load either to the earth or to supporting piles; the most common footing is the concrete slab. “Footer” is a local term for footing.5
The supporting material upon which the substructure portion of a bridge is placed.2
Freeboard High Water surface elevation
The clearance between the lower limit of the bridge superstructure or the bottom
A type of escape structure that uses a narrow entrance to discourage large animals from entering the ends of barrier fencing, and allows escape several meters away from the ends through one-way gates or other structures.13
Made of high-tensile steel, this material is comprised of multiple stands of horizontal and vertical wires woven into a mesh.
Steel Post with triangular side supports to be inserted into the corresponding stake pocket mounted on the outside edge of the cattle guard inline with the fence. It is used to support a swinging style farm gate and attaches to the fence on row side. See Photo
Main horizontal support beam, usually supporting other beams.13
In-roadway barrier, grid span, for various species of goats, pigs, wild hogs, peccary. Typically, 8’- 10’ in the driving distance. Includes knife edge, and angle iron beam protection (Pig Stop Technology). Includes multi-color, yellow and white, paint job. It is also recommended to paint three 20 “ stripes arranged yellow, white, yellow in front of the grid span to further discourage the goats from approaching or crossing.
Crossing of two highways, or a highway and a railroad, at different levels.8
Gross Vehicle Weight (GVW)
The maximum total weight of a traffic vehicle.2
Hold Down Clip
Rectangular steel washers used to overlap the flange of an adjacent beam flange. Hold down clip goes over the embedded bolt in the abutment of a grid span, usually at each corner. See Diagram
Support structures for vehicles built over a pit and used to prevent wildlife access across a break in fencing or other barrier.7
A dynamic load that is applied to a structure suddenly or that is accompanied by vibration, oscillation, or other physical condition affecting its intensity.2
In-roadway barrier, grid span, for various species of large deer and antelope including Kudu, Red Stag and Elk. Typically, 14’- 16’ in the driving distance.
A reflective sign mounted on a post, w is used to warn road users of obstructions that are adjacent to or within the extent of the roadway. Often used to mark the outer edge of a bridge or cattle guard.
(Standard) Object Marker:
When used, object markers (see Figure 3C-1) shall consist of an arrangement of one or more of the following types:8
- Type 1 Object Marker —either a marker consisting of nine yellow retroreflectors, each with a minimum diameter of 3 in, mounted symmetrically on a yellow (OM1-1) or black (OM1-2) diamond panel 450 mm (18 in) or more on a side; or on an all-yellow retroreflective diamond panel (OM1-3) of the same size:8 See Photo
- Type 2 Object Marker —either a marker (OM2-1V or OM2-1H) consisting of three yellow retroreflectors, each with a minimum diameter of 3 in, arranged either horizontally or vertically on a white panel measuring at least 6 x 12 in, or on an all-yellow horizontal or vertical retroreflective panel (OM2-2V or OM2-2H), measuring at least 6 x 12 in:8 See Photo
- Type 3 Object Marker —a striped marker, 12 x 36 in, consisting of a vertical rectangle with alternating black and retroreflective yellow stripes sloping downward at an angle of 45 degrees toward the side of the obstruction on which traffic is to pass. The minimum width of the yellow and black stripes shall be 3 in.8 See Photo
A gate (or ramp) designed to allow passage for the design species in only one direction, so that it can leave a highway but have difficulty accessing it. Type of Escape Structure.10
In general, any load that is in excess of the design load.2
In-roadway barrier, grid span, for various species of peccary. Typically, 8’ in the driving distance. Includes knife edge, and angle iron beam protection (Pig Stop Technology).
In-roadway barrier, grid span, for various species of pigs, Russian boars, and wild hogs. Typically, 10’- 12’ in the driving distance. Includes knife edge, and angle iron beam protection (Pig Stop Technology).
The act of placing and curing concrete within formwork to construct a concrete element offsite, then transporting to final position.
The vehicle live load used for design, which represents the maximum load level that can use the structure on a continual basis.2
In-roadway barrier, grid span, for various species of sheep, goats, pigs, wild hogs, peccary. Typically, 8’- 10’ in the driving distance. Includes knife edge, and angle iron beam protection (Pig Stop Technology)
Steel and Timber Base
Portable Base system that can be transported to remote locations such as jeep trails. Typically used by the USFS, they can be installed without the use of heavy equipment.
Steel Wing Posts
Posts made of Cattle Guard Cap used to make the connection between the fence and the cattle guard wing.
Load-bearing skeleton of a structure that resists all imposed and applied forces and loads.8
Soil prepared and compacted to support aggregate, paved surface, a concrete slab, or other construction.8
All of the structure below the bearings of simple and continuous spans, skewbacks of arches, and tops of footings of rigid frames, together with the backwalls, wingwalls, and wing protection railings. The entire structure excluding the substructure.3
The top layer of a pavement structure, sometimes called the wearing course, usually designed to resist skidding, traffic abrasion, and the disintegrating effects of climate.3
In-roadway barrier, grid span, for various species of endangered tortoise species. Developed by the USBLM with help from Big R Bridge for the Mojave Desert tortoise which occurs north and west of the Colorado River in California, Nevada, Arizona, and Utah. Used in conjunction with Tortoise fence to keep tortoise out of an area or off a roadway. Typically Tortoise Fence: Typical 4 strand wire fence with the addition of 1” x 2” Galvanized mesh panels. Posts spaced at 10’ intervals. The bottom 12” of mesh panel is below ground and 24” is above ground. The bottom wire is attached to the top of the mesh panel with hog rings.
A crossing structure allowing animals to pass under traffic. Underpasses can be broadly categorized as either bridges or culverts.10
Escape structures primarily for deer that consist of a narrow opening in a livestock fence that is blocked by a single post. Livestock can normally not wriggle through the tight corners, but smaller and more flexible deer can. Sometime called Wriggle Gates.10
Collisions between any wildlife species and vehicles, usually on highways. Normally this results in the animal’s death as well as property damage and possible injury or death to people.10
Triangular attachment, wherein the base is of similar width to that of the grid, and the top offers a single attachment point to the last post of a fence line. Wings are used to prevent animals from going around the end post to avoid the grid.
The working load is the actual load on the structure is used and the method of analysis is based on the elastic behavior of the material. The design is control by using a specified limit of stress.
- References -
1Singleton, P. 2000. Preliminary Glossary of Biological and Landscape Ecology Terms Relating to the Ecological Impacts of Highways. Unpublished. U.S. Department of Agriculture Forest Service, Wenatchee Forest Sciences Library, Wenatchee, WA.
2U.S. Department of Agriculture, Forest Service. 1990. Timber Bridges Design, Construction, Inspection, and Maintenance. EM 7700-8 Engineering Staff. Section 17. 16pp.
3U.S. Department of Agriculture, Forest Service. 1996. Forest Service Specifications for Construction of Roads & Bridges. Engineering Staff Section 102. EM-7700-100 Washington, DC. 7pp.
4U.S. Department of Transportation, Federal Highway Administration. 1998. Federal Lands Highway Project Development and Design Manual. 27pp.
5U.S. Department of Agriculture, Forest Service. 2000. Identifying and Preserving Historic Bridges. 0071-2854-MTDC Section 1. 27pp.
6Webster, L.F. 1995. The Wiley Dictionary of Civil Engineering and Construction. John Wiley & Sons, Inc.
11Hoy, James F. (2004), “Cattle Guards”, Encyclopedia of the Great Plains, by David J. Wishart, University of Nebraska Press, p. 292, ISBN 9780803247871