cattle guard

A cattle grid or cattle guard – also known as a vehicle pass, Texas gate, or, in New Zealand, a cattle stop – is a type of obstacle used to prevent livestock, such as sheep or cattle, from passing along a road which penetrates the fencing surrounding an enclosed piece of land. It consists of a depression in the road covered by a transverse grid of bars or tubes, normally made of metal and firmly fixed to the ground on either side of the depression, such that the gaps between them are wide enough for animals' legs to fall through, but sufficiently narrow not to impede a wheeled vehicle. They rely for their effect (of barring passage to animals but not to wheeled vehicles) upon animals' reluctance to set foot upon them.

A cattle guard on California State Route 76 near Lake Henshaw.

Cattle grids are usually installed over roads where they cross a fenceline, often at a boundary between public and private lands. They are an alternative to the erection of gates that would need to be opened and closed every time a vehicle passed, and are common where roads cross open moorland, rangeland or common land maintained by grazing, but where segregation of fields is impractical. Cattle grids are also used when otherwise unfenced railways cross a fenceline. Cattle grids are seen throughout the world and quite common in places such as Australia, the Scottish Highlands, or the National Parks of England and Wales. They are also common throughout the Western United States and Canada, where they are usually called a cattle guard or, occasionally, a Texas gate. In the USA, they are most often used on BLM and Forest Service land, but are also used on paved roads and even exit ramps of the Interstate Highway System in many rural areas.

A cattle grid and straying sheep

While these barriers are usually effective, they can fail due to ingenious animals. Sheep have been known to jump or run along the side of grids as wide as 8 feet (2.4 m), traversing them in order to find more and better food or water. Wider grids are used where deer are to be contained. Some animals, particularly wildlife, can jump across them, and animals with particularly large feet, such as American bison or even particularly large bovine bulls, can walk across them without slipping between the bars. Sometimes they may be connected to an electric fence to prevent predatory animals, such as dingoes and foxes walking over them. In areas with heavy snowfall and long periods without a thaw, snow can fill up under a grid and allow animals to walk across it.

A "virtual grid" near Lone Pine, California

Portable "Texas gates" suspend the gate by springs so that it lowers to the ground when a vehicle passes over then returns to a position 6 inches (15 cm) above the ground.

Painted lines on the road can serve as skeuomorphs of cattle grids. The light-dark pattern of lines and pavement resembles a true cattle guard to animals. Many animals see a more intense contrast between light and dark because^{[dubious – discuss]} their night vision is much better than humans'. Animals see the sharp contrast of the cattle guard on the ground as a false visual cliff; they act as if the dark spots are deeper than the light spots. Using a virtual cattle guard is cheaper than a true cattle guard, and can be used on higher-speed roads due to its smooth surface.^[1]

There is a British Standard for cattle grids: BS4008:2006. The US standards are put forth by The American Association of State Highway Transportation Officials (AASHTO). AASHTO provides load rating guidelines for cattle guards that are used on public roads in America. All cattle guards used on American public roads must be certified by a qualified engineer that the guard meets AASHTO guidelines. ^[2]

See also

• Bus trap
• Bump gate
• Ha-ha

References

Wikimedia Commons has media related to: Cattle grids