A bollard is a short vertical post typically found where large ships dock. While originally it only meant a post used on a quay for mooring, the word now also describes a variety of structures to control or direct road traffic. The term may be related to bole, meaning the lower trunk of a tree.
A bollard, a name inherited from the Norman-French name Boulard still often found in Normandy, is a short wooden, iron or stone post used on a quayside for mooring ships. Mooring bollards are rarely totally cylindrical, but typically have a larger diameter near the top to discourage mooring warps (docklines) from coming loose. Single bollards will sometimes include a cross rod to allow the mooring to be bent into a figure eight.
Tall (1.15 meter/4 foot) slim (10 cm/4 inch) fluorescent red or orange plastic bollards with reflective tape and removable heavy rubber bases are frequently used in road traffic control where traffic cones would be inappropriate due to their width and ease of movement. Also referred to as deliniators, the bases are usually made from recycled plastic, and can be easily glued to the road surface to resist movement following minor impacts from passing traffic. Sometimes called "T-Top Bollards" from the T-bar moulded into the top for tying tape, the bollard is an economical, cost effective and safe delineation system designed especially for motorways and busy arterial roads. In conjunction with plastic tape, it is also effective in pedestrian control.
The American Heritage Dictionary describes this use of Bollard as "chiefly British", although the term has crept into the jargon of some American universities where dense traffic necessitates the use of bollards for Access Control.
Bollards are frequently used to direct traffic around a traffic island. A recent development is the "rising bollard" - a bollard that can be lowered entirely below the road surface to enable traffic to pass, or raised to block traffic. Rising bollards are used to secure sensitive areas from attack, or to enforce traffic rules that are time related or restrict access to particular classes of traffic.
A "manually retractable bollard", however is lowered by a key mechanism. It is especially useful in a mixed-use public space which supports both pedestrian use and emergency and or service vehicle use.
The term "robotic bollards" has been applied to traffic barricades capable of moving themselves into position on a roadway.
Permanent and retractable buried bollards are increasingly common around the world to hinder vehicle-based terrorist actions from achieving close proximity to buildings, and are also used to prevent Ram-raiding.
Bollards are also used as a form of permanent utility location.