Bollard limit vehicular access to specified areas while providing various levels of security to facilities and pedestrians. Bollards allow unimpeded pedestrian passage, unlike barriers.Bollards come in a number of styles and provide different levels of security with a variety of aesthetic characteristics. Retractable or removable bollards are available for situations requiring only occasional access for authorized or emergency vehicles.
Bollards can be constructed of concrete, steel, cast iron, or plastic in a variety of forms and sizes.Bollards have become more prevalent in facility designs because of their high level of public acceptance. They guide and deter vehicles by their presence, but do not impede pedestrian traffic. During vehicular intrusion attempts, bollards absorb kinetic energy and inflict vehicle damage.
Fixed Bollards
Fixed bollards, , offer a high degree of cost effective protection. They are commonly placed in and around airports, federal buildings, and other public facilities where vehicle control is required, but foot traffic must be unimpeded. Fixed bollards are generally made
from tubular steel or cast iron. Some are filled with concrete for added strength. The subsurface engineering of fixed bollards depends on the required level of protection.
Removable Bollards
Removable bollards may be required to create an emergency access route through a controlled perimeter or to increase security on an occasional basis. Removable bollards lock into place and often have a cap to cover the foundation when the bollard is removed. These devices are generally less protective than fixed bollards, because the foundation is less robust.
Retractable or Automatic Bollards
Retractable bollards, , are generally operated by hydraulic or pneumatic power units and can be lowered into the ground to allow authorized or emergency vehicles to pass. These bollards can return to full height in the event of a security threat. A manual method of operating them during a power or system failure is a standard feature. The subsurface engineering depends on the required level of protection.
Manual and Semi-Automatic Removable Bollards
Manual and semi-automatic bollards cost less than fully automatic bollards and offer similar access control effectiveness. These devices may be suitable when the quick response of automatic bollards is not necessary.
Semi-automatic bollards must be unlocked to change the position from raised to retracted or vice versa.Compressed gas is often used to raise a semi-automatic bollard; although a hand crank or pull system may also be used. Manual and semi-automatic bollards are essentially designed and installed in the same manner as automatic bollards, differing only in the manner in which they are deployed.
Portable Bollards
Portable bollards range from lightweight plastic devices to concrete versions that must be moved using lifting equipment. Portable bollards generally do not attach to a foundation. Lightweight plastic versions are often covered with reflective tape and are used in the same manner as traffic cones to warn the public of hazardous conditions or of a temporary denial of vehicle access. They may be used to restrict vehicular traffic temporarily for a parade or other social event. Portable concrete bollards require mechanical assistance for transportation and placement. These are often used to augment vehicular access control during periods of increased security threat levels.
Bollards Applications
Bollards are primarily used for exterior applications, but are useful in interior applications where vehicles may be present, such as warehouses, parking garages, arenas, or stadiums. In building interiors, bollards may be placed to protect critical infrastructure such as power control units, air conditioning units, pedestrian access areas, or locations where a separation between vehicle and pedestrian traffic is needed.
In exterior applications, bollards can be used to define a vehicle free area or to restrict vehicle traffic from certain routes and roadways. Typical uses of portable bollards are to protect parking spaces, prevent vehicles from blocking a driveway, or provide a warning of a safety hazard.
Performance Metrics
ASTM International Designation F 2656-07 defines systematic test standards using real crash tests to quantify, verify, and certify barrier performance. Prior to receiving certification, manufacturers must have their products tested by an approved independent crash test organization to demonstrate that they meet ASTM standards.
Vulnerabilities
When it comes to bollard , visibility is the most important safety issue. Retractable bollards may be triggered without a pedestrian noticing. Many vendors offer custom colors which make the bollards more visible. Most bollards have highly reflective labels which help further improve visibility.
references :
- Access Control Technologies Handbook