Traffic bollards are used to highlight traffic islands. They are primarily used at intersections within the splitter islands (a raised or painted area on the approach of a roundabout used to separate entering from exiting traffic, deflect and slow entering traffic, and provide a stopping place for pedestrians crossing the road in two stages). Illuminated bollards are also used to supplement street signs and street lighting to provide a visual cue to approaching drivers that an obstacle exists ahead during hours of darkness and during periods of low visibility: Internally illuminated traffic bollards have been in existence throughout the United Kingdom and Ireland since the 1930s, although the term "bollard" only seems to have been in common use since the late 1940s. An illuminated bollard has a recessed base light unit in the foundation to illuminate the traffic bollard from all angles. The main components are housed below the road or pedestrian surface (typically a concrete surface). Therefore, if a vehicle strikes the traffic bollard, the units below the surface are not damaged. In addition, most new modern traffic bollards installed along UK roadways today are made of materials that make them completely collapsible. When struck by a vehicle at low or high speed, the traffic bollard shell reverts to its original position with minimal to no damage to the unit. Reflective bollards may also be used; they need no power or maintenance, and can be built to recover to their normal position after being struck. Bell A bell bollard is a style of bollard designed to deflect vehicle tires. The wheel mounts the lower part of the bollard and is deflected by its increasing slope. Such bollards are effective against heavy goods vehicles that may damage or destroy conventional bollards or other types of street furniture. Retractable Manually retractable bollards (lowered by a key mechanism) are found useful in some cases because they require less infrastructure. The term "robotic bollards" has been applied to traffic barricades capable of moving themselves into position on a roadway. Self-righting or self-recovering bollards can take a nudge from a vehicle and return to the upright position without causing damage to the bollard or vehicle. They are popular in car park buildings and other areas of high vehicle usage. Flexible Flexible bollards are bollards designed to bend when struck by vehicles. They are typically made from synthetic plastic or rubber that is stiff on