Cattle grid

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For a device commonly referred to as a "cow catcher", see Pilot (locomotive).

Cattle grid in remote Western Australia.

A cattle grid or cattle guard, also known as a vehicle pass, or in New Zealand as a cattle stop, is a type of obstacle used to prevent hoofed animals, such as sheep or cows, from passing. It consists of a grid of bars or tubes, usually made of metal, firmly fixed on the ground with a depression underneath so that the gaps between them are wide enough for animals legs to fall through, but narrow enough that a vehicle's wheels will not. A cattle grid will allow wheeled vehicles to pass through the entrance, but will contain animals within the enclosure because they will refuse to step on the grid.

Cattle guard on State Route 76 near Lake Henshaw.

These grids are usually installed over countryside roads where they cross a fenceline, often at a boundary between public and private lands. The alternative is to create a gate that would need to be manually or automatically opened when a vehicle comes. They are common where roads cross open moorland or common land maintained by grazing, but where segregation of fields is impractical, such as in the Scottish Highlands or the National Parks of England and Wales. They are also common throughout the Western United States and Canada, particularly on BLM and Forest Service land, where they are usually called a cattle guard, or, occasionally, a "Texas gate." Cattle grids are also used when otherwise unfenced railways cross a fenceline.

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. Some animals, particularly wildlife, can jump across them, and animals with particularly large feet, such as American bison or even particularly large cattle herd bulls, can walk across them without slipping between the bars. 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.

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.

"Virtual" cattle grids can also be used. These look like cattle grids, but are only painted lines on the highway. The light-dark pattern of lines and pavement resembles a true cattle guard to animals. Animals see more intense contrasts of light and dark because their night vision is so much better than ours. 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.