Gate Barrier System
A Gate Barrier is a bar, or pole pivoted to allow the boom to block vehicular access through a controlled point. Typically the tip of a boom gate rises in a vertical arc to a near vertical position.
Boom gates often counterweighted, so the pole is easily tipped. Boom gates are often paired either end to end, or offset appropriately to block traffic in both directions. Some boom gates also have a second arm which hangs 300 to 400 mm below the upper arm when lowered, to increase approach visibility, and which hangs on links so it lies flat with the main boom as the barrier is raised.
They are also the usual method for controlling passage through toll booths, and can also be found on some parking areas which are automatically controlled to drop to restrict.