Barrier cables are used to create obstructions that can restrain both vehicles and pedestrians. The most common use for barrier cable is in parking garages, though some transportation authorities also use it for the construction of road medians and guardrails. Barrier cable systems consist of strong, metal cables that are strung between concrete or metal posts. The tensile strength offered by barrier cable is often enough to stop a moving vehicle, and the presence of the obstruction can also keep pedestrians from falling over the edge of a structure. Cables used for these types of barriers can be galvanized or coated in an epoxy or plastic to prevent wear.
The metal strands used in barrier cables are similar to those used with post-tensioned concrete. A typical barrier cable consists of seven wires that are about a half inch (1.2 centimeter) in diameter. The wires are woven together to create a resilient cable with excellent tensile strength. These cables are then strung between metal or concrete posts, often in several parallel rows. More rows of barrier cable can provide additional stopping power, and barriers constructed in this manner are often capable of stopping trucks and other very large vehicles.
A variety of methods are used to protect the cables used in these systems. The majority of barrier cables use a zinc galvanization process to protect them from corrosion. Epoxy and plastic coatings are also used, though these tend to be more expensive. A particular aesthetic can often be achieved by epoxy coatings, while plastic coated barrier cables are nearly identical to those used in most post-tensioned concrete structures.
One benefit of barrier cable systems is the increased visibility compared to solid obstructions. The loss of visibility caused by solid barriers is often a concern in parking garages, where vehicles may hit each other when turning tight corners. Barrier cables can be used to create obstructions that can easily be seen through, allowing vehicles to maintain visual contact and avoid accidents. Rooftop parking structures can also benefit from this extra visibility, since any views available from the top of the building will not be fully obstructed by the barrier cables.
Visibility can also be an issue when constructing road medians and guardrails, especially at intersections and corners. Large concrete medians can impede the ability of drivers to see oncoming traffic when turning, so a system using barrier cables can lead to better road safety. Studies have suggested that barrier cable medians can stop 95% of vehicles from crossing into oncoming traffic. It can also be one of the most cost effective solutions when compared to concrete and other solid barriers.