This article needs additional citations for verification .(May 2022)
A bollard is a sturdy, short, vertical post. The term originally referred to a post on a ship or quay used principally for mooring boats. It now also refers to posts installed to control road traffic and posts designed to prevent automotive vehicles from colliding or crashing into pedestrians and structures, whether intentional from ram-raids and vehicle-ramming attacks, or unintentional losses of control.
The term is probably related to bole, meaning a tree trunk.    The earliest citation given by the Oxford English Dictionary (referring to a maritime bollard) dates from 1844,  although a reference in the Caledonian Mercury in 1817 describes bollards as huge posts. 
Wooden posts were used for basic traffic management from at least the beginning of the 18th century. An early well-documented case is that of the "two oak-posts" set up next to the medieval Eleanor cross at Waltham Cross, Hertfordshire, in 1721, at the expense of the Society of Antiquaries of London, "to secure Waltham Cross from injury by Carriages". 
In the maritime contexts in which the term originates, a bollard is either a wooden or iron post found as a deck-fitting on a ship or boat, and used to secure ropes for towing, mooring and other purposes; or its counterpart on land, a short wooden, iron, or stone post on a quayside to which craft can be moored. The Sailor's Word-Book of 1867 defines a bollard in a more specific context as "a thick piece of wood on the head of a whale-boat, round which the harpooner gives the line a turn, in order to veer it steadily, and check the animal's velocity".   Bollards on ships, when arranged in pairs, may also be referred to as "bitts".  
Bollards can be used either to control traffic intake size by limiting movements, or to control traffic speed by narrowing the available space. Israel's Transportation Research Institute found that putting bollards at highway exits to control traffic also reduced accidents. 
Permanent bollards can be used for traffic-control or guarding against vehicle-ramming attacks.  They may be mounted near enough to each other that they block ordinary cars/trucks, for instance, but spaced widely enough to permit special-purpose vehicles, bicycles, and pedestrians to pass through. Bollards may also be used to enclose car-free zones. Bollards and other street furniture can also be used to control overspill parking onto sidewalks and verges. 
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. 
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. 
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 bollards are bollards designed to bend when struck by vehicles. They are typically made from synthetic plastic or rubber that is stiff on its own, but pliable under the weight of a car or truck. When struck, flexible bollards give way to some extent, reducing damage to vehicles and surrounding surfaces, and return to their original, upright position. Some flexible bollards do not provide physical protection from vehicles; rather they offer clear visual guidance for drivers. Other flexible bollards have been designed to provide physical protection as well as reduced damage by incorporating strong elastic materials. These can be all plastic or plastic/steel hybrids but combine varying degrees of stopping power and flexibility.    
Bollards are used by government agencies and private businesses to protect buildings, public spaces, and the people in them from car ramming attacks. 
These bollards protect utilities, electronics, machinery, buildings, or pedestrians from accidental or intentional collisions with vehicles. As collisions also cause damage to vehicles, operators, or the bollards themselves, new bollards have been developed that absorb some of the impact energy, lessening the violence of the collision. Some are made of forgiving plastics while others are made of steel but fitted with an elastomer to absorb the impact energy. 
Bollards are widely used to contribute to safety and security. The American Bar Association (ABA) states that bollards are used to contribute to homeland security.  The American National Institute of Building Sciences site—the Whole Building Design Guide (WBDG)—recommends in its Design Guidance that open spaces surrounding and contiguous to buildings be included as integral parts of a security design. 
There are two main kinds of security-related bollard:
According to the National Institute of Building Sciences, non-crash-resistant bollards are "perceived impediments to access" and address the actions of two groups:
High security bollards are impact-tested in accordance with one or more of three major crash test ratings for vehicle barriers. These are PAS 68 (UK),  IWA-14 (International) and ASTM (US).  
Bollard sleeves in various alloys or finishes are designed to cover security bollards to enhance their visual attractiveness. 
U-shaped bollards are typically used for the protection of equipment and are common in areas that need coverage over a wider area than of a normal bollard, such as fuel stations and bike lanes. 
Bollards have become common use for reserving parking spots from unauthorized vehicles.  Parking bollards are typically situated in the centre of a parking bay as a physical obstruction. They then fold either manually or automatically to admit authorized users. These bollards are often used in smaller parking lots such as visitor parking or corporate parking lots, as an alternative to boom gates. They can be powered by a wide variety of means, with the most common being battery-powered or electric-powered.
The National Clearinghouse for Educational Facilities (NCEF), managed by the National Institute of Building Sciences (NIBS), cited three dozen applications of bollards.  
According to the International Fire Code (IFC-2009) and the American National Fire Protection Association Fire Code 1 (NFPA-1) all new buildings or renovated buildings must have fire access roadways to accommodate fire apparatus and crews and other first responders. Thus the choice of bollard styles must apply to the NFPA's Code 1710. Bollards are now designed in terms of how long it takes to remove or collapse them to allow first responders entry to the access roadway.  
In Geelong, Victoria, Australia, decorative bollards, sculpted and painted by Jan Mitchell, are placed around the city to enhance the landscape as a form of outdoor public sculpture. Usually they are made of timber, minimally modified from the traditionally cylindrical, wooden, maritime bollard shape, but brightly painted to resemble human figures. Such figures – which may be historical or contemporary, particular or generic – are sited singly or in clusters along the waterfront and in other areas where people gather. Decorative bollards have become a well-known feature of the city of Geelong and reflect its history as a major Australian port. 
In Antwerp, Belgium, artist Eddy Gabriel transformed a bollard to look like a toadstool in 1993. This example was followed by other artists, turning the quayside of the river Scheldt into a street art gallery. 
In Norwich, England, a set of 21 bollards was installed in 2008 in the Lanes area north of City Hall, designed by artist Oliver Creed and commissioned by the City Council as part of a regeneration programme.  They are coloured "madder red", in reference to the red dye extracted from the madder plant and used for dying cloth, one of the city's major industries during the 16th century; and they bear bronze finials also alluding to local history. 10 of these depict the madder plant, while the other 11 have unique designs, usually relevant to the specific location in which the bollard is placed, including a scene of sheep-shearing, a Green Man, a swan's head in Swan Lane, and so on. 
On the forecourt of Cambridge University Library, England, a line of 14 bronze bollards made to resemble piles of books was installed in 2009. This work, Ex Libris, was created by sculptor Harry Gray. The ten outer bollards are static, but the "books" making up the four central bollards can be swivelled, so that the lettering on their spines aligns to form the Latin phrase Ex Libris ("from/out of the books"), commonly used on bookplates.   
A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles and pedestrians. Unlike streets, the main function of roads is transportation.
A sidewalk, pavement, footpath in Australia, India, New Zealand and Ireland, or footway, is a path along the side of a street, highway, terminals. Usually constructed of concrete, pavers, brick, stone, or asphalt, it is designed for pedestrians. A sidewalk is normally higher than the roadway, and separated from it by a kerb. There may also be a planted strip between the sidewalk and the roadway and between the roadway and the adjacent land.
An intersection or an at-grade junction is a junction where two or more roads converge, diverge, meet or cross at the same height, as opposed to an interchange, which uses bridges or tunnels to separate different roads. Major intersections are often delineated by gores and may be classified by road segments, traffic controls and lane design.
A pedestrian crossing is a place designated for pedestrians to cross a road, street or avenue. The term "pedestrian crossing" is also used in the Vienna and Geneva Conventions, both of which pertain to road signs and road traffic.
Traffic lights, traffic signals, or stoplights – known also as robots in South Africa – are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control flows of traffic.
Traffic calming uses physical design and other measures to improve safety for motorists, pedestrians and cyclists. It has become a tool to combat speeding and other unsafe behaviours of drivers in the neighbourhoods. It aims to encourage safer, more responsible driving and potentially reduce traffic flow. Urban planners and traffic engineers have many strategies for traffic calming, including narrowed roads and speed humps. Such measures are common in Australia and Europe, but less so in North America. Traffic calming is a calque of the German word Verkehrsberuhigung – the term's first published use in English was in 1985 by Carmen Hass-Klau.
Road traffic safety refers to the methods and measures used to prevent road users from being killed or seriously injured. Typical road users include pedestrians, cyclists, motorists, vehicle passengers, horse riders, and passengers of on-road public transport.
Street furniture is a collective term for objects and pieces of equipment installed along streets and roads for various purposes. It includes benches, traffic barriers, bollards, post boxes, phone boxes, streetlamps, traffic lights, traffic signs, bus stops, tram stops, taxi stands, public lavatories, fountains, watering troughs, memorials, public sculptures, and waste receptacles.
A curb extension is a traffic calming measure which widens the sidewalk for a short distance. This reduces the crossing distance and allows pedestrians and drivers to see each other when parked vehicles would otherwise block visibility.
Guard rail, guardrails, or protective guarding, in general, are a boundary feature and may be a means to prevent or deter access to dangerous or off-limits areas while allowing light and visibility in a greater way than a fence. Common shapes are flat, rounded edge, and tubular in horizontal railings, whereas tetraform spear-headed or ball-finialled are most common in vertical railings around homes. Park and garden railings commonly in metalworking feature swirls, leaves, plate metal areas and/or motifs particularly on and beside gates.
A junction is where two or more roads meet.
A road diet, also called a lane reduction, road rechannelization, or road conversion is a technique in transportation planning whereby the number of travel lanes and/or effective width of the road is reduced in order to achieve systemic improvements.
A cycle track, separated bike lane or protected bike lane is an exclusive bikeway that has elements of a separated path and on-road bike lane. A cycle track is located within or next to the roadway, but is made distinct from both the sidewalk and general purpose roadway by vertical barriers or elevation differences.
Traffic barriers keep vehicles within their roadway and prevent them from colliding with dangerous obstacles such as boulders, sign supports, trees, bridge abutments, buildings, walls, and large storm drains, or from traversing steep (non-recoverable) slopes or entering deep water. They are also installed within medians of divided highways to prevent errant vehicles from entering the opposing carriageway of traffic and help to reduce head-on collisions. Some of these barriers, designed to be struck from either side, are called median barriers. Traffic barriers can also be used to protect vulnerable areas like school yards, pedestrian zones, and fuel tanks from errant vehicles.
A bicycle parking rack, usually shortened to bike rack and also called a bicycle stand, is a device to which bicycles can be securely attached for parking purposes. A bike rack may be free standing or it may be securely attached to the ground or some stationary object such as a building. Indoor bike racks are commonly used for private bicycle parking, while outdoor bike racks are often used in commercial areas. General styles of racks include the Inverted U, Serpentine, Bollard, Grid, and Decorative. The most effective and secure bike racks are those that can secure both wheels and the frame of the bicycle, using a bicycle lock.
Road traffic collisions generally fall into one of five common types:
A traffic collision, also called a motor vehicle collision, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other moving or stationary obstruction, such as a tree, pole or building. Traffic collisions often result in injury, disability, death, and property damage as well as financial costs to both society and the individuals involved. Road transport is the most dangerous situation people deal with on a daily basis, but casualty figures from such incidents attract less media attention than other, less frequent types of tragedy.
Cycling infrastructure is all infrastructure cyclists are allowed to use. Bikeways include bike paths, bike lanes, cycle tracks, rail trails and, where permitted, sidewalks. Roads used by motorists are also cycling infrastructure, except where cyclists are barred such as many freeways/motorways. It includes amenities such as bike racks for parking, shelters, service centers and specialized traffic signs and signals. The more cycling infrastructure, the more people get about by bicycle.
A protected intersection or protected junction, also known as a Dutch-style junction, is a type of at-grade road junction in which cyclists and pedestrians are separated from cars. The primary aim of junction protection is to make pedestrians and cyclists safer and feel safer at road junctions.
A stroad is a type of thoroughfare that is a mix between a street and a road. The word stroad is a portmanteau of street and road, coined by American civil engineer and urban planner Charles Marohn in 2011, as a commentary about paved traffic structures in the United States. The term has also been applied to various traffic situations in Canada.