The term bollard is used to describe a number of short vertical posts, originally used to describe mooring posts either on a ship or a quay. However, in modern times, the use of this term has expanded considerably, and it is now often used in context with road traffic control. A variety of permanent and retractable bollards (exclusiv-home.de) are regularly used in urban environments, as a way to control and direct road traffic and control parking and vehicle movement in busy places. For example, in cities, there is often a big difference in traffic flows at different times of the day, and retractable bollards can be used to cut off access roads and limit parking during peak hour times. Along with their use as a centralised road control device, retractable bollards are also often used outside busy urban apartment blocks to restrict parking access.
The term bollard probably comes from the term bole, which means tree trunk. The earliest reference of the term bollard comes from 1844, and before this time the term post was likely used. Retractable bollards are also known as movable bollards, and are able to fall below the road surface to enable traffic to pass. In essence, retractable bollards are used as a mechanism of traffic control, to secure sensitive areas, enforce time related traffic rules, and hinder vehicle access as a way to stop terrorism attacks.
The control of retractable bollards is restricted to certain people, depending on the type of bollard in question. Control of public road bollards is generally limited to the local authorities who control the roads, with parking bollards and those on private land limited to building owners and tenants. Along with differences in terms of application, retractable bollards also differ in terms of their mechanism. For example, some movable bollards are hinged at ground level and are fitted with a padlock, others can rise and fall with remote control, and others, called robotic bollards, are even capable of positioning themselves on a roadway. Retractable bollards play an important role in many urban environments, as a way to control the movement of traffic and obstruct road passages during certain times of the day.