Safety Barrier Glossary | A-Z of UK Barrier & Bollard Terms

This comprehensive A-Z glossary covers the key terms used in UK safety barrier, bollard, and traffic management specification. Whether you're reading a specification document, reviewing a quotation, or researching products for a project, this glossary provides clear definitions in UK context.

A

Armco Barrier

A corrugated W-beam (W-profile) steel crash barrier widely used on UK roads and in industrial settings. Named after the American Rolling Mill Company (ARMCO), the term is now used generically for any W-beam guardrail. Manufactured to BS EN 1317-2 for highway use; lighter "industrial grade" versions are available for private applications. Related terms: W-beam, guardrail, corrugated beam.

ASF (Automatic Swing/Folding Gate)

A powered gate system used for vehicle access control. Unlike a boom arm barrier, an ASF gate provides a physical barrier across the full width of the opening when closed. Used where full-closure security is required in addition to access control. Related terms: boom barrier, automatic rising bollard.

ASI (Acceleration Severity Index)

A measure used in BS EN 1317 testing that quantifies the acceleration forces experienced by vehicle occupants when the vehicle strikes a restraint system. ASI values are classified A (≤1.0), B (≤1.4), or C (≤1.9) — lower values indicate lower occupant injury risk. Related terms: THIV, BS EN 1317, normalised acceleration.

B

Beam Barrier

A horizontal barrier, typically steel, used for height restriction or vehicle access control. In the context of height restrictors, a beam barrier is a fixed or articulated horizontal member positioned at the maximum height clearance point of an entrance. Related terms: height restrictor, boom barrier.

Bollard

A short, sturdy vertical post used to control road traffic and provide barriers between road and pedestrian areas. UK bollards are manufactured in a wide range of materials (steel, stainless steel, concrete, HDPE plastic) and can be fixed, removable, telescopic, or automatic. May be certified to PAS 68 or IWA 14-1 for security applications. Related terms: fixed bollard, removable bollard, PAS 68, hostile vehicle mitigation.

Boom Barrier

A long horizontal arm (typically 3–6m) pivoted at one end and used as a vehicle access control barrier. Also known as a boom gate or barrier arm. Commonly used at car park entrances, controlled access points, and level crossings. Related terms: barrier arm, ASF gate, height restrictor.

BS EN

Prefix indicating a British Standard that is also a European Norm (EN). The BS EN prefix indicates the standard has been adopted from a European standard into the British Standards framework. Many safety barrier standards are BS EN standards — see BS EN 1317 (VRS), BS EN ISO 1461 (galvanising). The "ISO" qualifier indicates further adoption from an international standard. Related terms: BSI, UKCA marking, CE marking.

C

Cantilever

A structural element that is anchored at one end and projects horizontally, supported only at that anchor point. In barrier terms, cantilever gates use this principle — the gate is pivoted at one post with no track or bottom rail, allowing ground-level vehicle access without a threshold obstacle. Related terms: sliding gate, ASF gate.

Chapter 8

Chapter 8 of the Traffic Signs Manual (published by the Department for Transport) — the governing document for temporary and permanent traffic management on roads in England. Chapter 8 specifies the design, signing, and equipment requirements for roadworks traffic management, including barrier specifications. Compliance with Chapter 8 is mandatory for works on adopted public highways. Related terms: Traffic Signs Manual, TSRGD 2016, Highways Act.

Chevron

A V-shaped marking or sign. In traffic management, chevron signs (triangular yellow/black or white/black patterns on road delineators) are used to guide vehicles around hazards. Armco barriers are often fitted with retroreflective chevron delineators at bends and obstacle ends. Related terms: delineator, retroreflective, Chapter 8.

Collision Energy

The kinetic energy delivered by a striking vehicle at the point of impact, calculated as ½mv² (half of mass × velocity squared). BS EN 1317 and PAS 68 tests are categorised by vehicle mass and test speed, which together define the collision energy the restraint system must absorb. Related terms: BS EN 1317, PAS 68, containment level.

Containment Level (Class)

In BS EN 1317, the containment level (T1, T2, T3, N1, N2, H1, H2, H3, H4a, H4b) defines the severity of vehicle that a VRS has been tested and certified to contain. N classes test cars; H classes test HGVs and coaches. Higher classes indicate more severe vehicle containment capability. Related terms: BS EN 1317, performance class, N2, H1.

Corrugated Beam

The W-profile (W-beam) or thrie-beam corrugated steel rail used in Armco-type safety barriers. The corrugated profile provides a combination of longitudinal flexibility (allowing the barrier to deform gradually and distribute impact energy along its length) and transverse stiffness (resisting direct penetration). Related terms: W-beam, thrie-beam, Armco, guardrail.

Crash Cushion

An energy-absorbing device designed to protect a fixed obstacle (bridge pier, end of barrier, concrete structure) by absorbing the kinetic energy of an impacting vehicle, decelerating it in a controlled manner. BS EN 1317-3 covers crash cushion performance classes. More expensive than a simple terminal but justified at high-risk fixed hazard locations. Related terms: terminal, softnose terminal, BS EN 1317-3.

CTR (Containment Test Result)

The documented result of a PAS 68 or IWA 14-1 impact test, recorded in a standard notation that includes vehicle mass, category, test speed, impact angle, and penetration distance. The CTR is the primary evidence of a product's security performance — always request the CTR from a supplier when specifying HVM products. Related terms: PAS 68, IWA 14-1, hostile vehicle mitigation.

D

Delta Barrier

A water-filled HDPE temporary barrier system manufactured in a triangular cross-section (delta shape), providing stability without requiring tipping chains. Widely used in UK traffic management and at events. Some delta barrier variants are PAS 68 or IWA 14-1 rated for hostile vehicle mitigation applications. Related terms: water-filled barrier, temporary barrier, PAS 68.

Deflection

The lateral movement of a Vehicle Restraint System when it is struck by a vehicle. Dynamic deflection (D) is the maximum distance the barrier face moves during impact. Working width (W) is the total lateral space occupied by the barrier and any deflected vehicle — the critical clearance dimension for design. Related terms: working width, BS EN 1317, dynamic test.

Drop Arm

An alternative term for a boom barrier arm — a pivoted horizontal bar used as a vehicle access control barrier. "Drop arm" describes the action of the barrier dropping into the closed position to prevent vehicle access. Related terms: boom barrier.

Dynamic Test

An impact test conducted under BS EN 1317, PAS 68, or IWA 14-1 in which a vehicle or vehicle sled is crashed into the barrier system at the specified speed and angle to measure containment performance and occupant risk. Dynamic tests are the definitive evidence of a barrier's performance — as distinct from static load tests. Related terms: BS EN 1317, PAS 68, CTR, containment level.

E

End Terminal

The treatment applied to the end of a safety barrier run to prevent the open end of the barrier acting as a hazard to impacting vehicles. Proper end terminals flare away from traffic, fold flat on impact, or incorporate a softnose energy-absorbing system. On public highways, BS EN 1317-4/-7 compliant terminals are required. Related terms: softnose terminal, crash cushion, Armco.

F

Fixed Bollard

A bollard that is permanently installed in the ground — typically root-mounted in a concrete foundation or core-filled — and cannot be moved without excavation. Fixed bollards provide the highest level of physical deterrence and are preferred where no vehicle access will ever be required. Related terms: removable bollard, telescopic bollard, automatic rising bollard.

G

Galvanising

A corrosion protection process in which steel is coated with zinc. Hot-dip galvanising (the most common process for barrier and bollard products) involves immersing the steel article in molten zinc at approximately 450°C. The resulting zinc-iron alloy coating provides long-term corrosion protection specified by BS EN ISO 1461. Related terms: BS EN ISO 1461, powder coating, corrosion protection.

Guardrail

A longitudinal barrier system used along the edges of roads to prevent vehicles from leaving the carriageway. Guardrails are typically constructed from W-beam (Armco) or thrie-beam corrugated steel profiles mounted on steel posts. UK highway guardrails must comply with BS EN 1317-2. Also used in pedestrian contexts to separate pedestrians from vehicles (pedestrian guardrail, BS 7818). Related terms: Armco, W-beam, BS EN 1317, vehicle restraint system.

H

HAPAS (Highways Authority Product Approval Scheme)

A certification scheme operated jointly by the British Board of Agrément (BBA) and the Highways England (now National Highways) for products used on the strategic road network in England. HAPAS certification provides assurance that a product meets the technical requirements for use on motorways and major roads. Related terms: UKCA, CE marking, BS EN 1317.

Height Restrictor

A physical device installed at the entrance to a covered car park, low bridge, or restricted-height area to prevent vehicles exceeding the maximum height clearance from entering. Typically consists of a rigid beam (fixed) combined with a warning device (LED sensors, hanging rubber or chain "soft" beam) and advance warning signage. Related terms: beam barrier, car park safety.

HVM (Hostile Vehicle Mitigation)

The physical and procedural measures used to protect people and buildings from deliberate vehicle-as-weapon attacks. Physical HVM products are tested and certified to PAS 68:2013 or IWA 14-1:2013. HVM is specified in response to a threat assessment and typically in consultation with a CTSA (Counter Terrorism Security Adviser). Related terms: PAS 68, IWA 14-1, CTR, crowded places.

I

IWA 14-1

IWA 14-1:2013 — International Workshop Agreement published by ISO — the current international standard for vehicle security barrier (HVM) impact testing. Supersedes PAS 68 for new product certifications. Uses similar notation to PAS 68 but with some differences in vehicle categories and test conditions. Related terms: PAS 68, HVM, CTR.

J

Jersey Barrier

A precast concrete barrier with a distinctive trapezoidal cross-section (vertical bottom, sloped upper section) originally developed in New Jersey, USA. Used on UK roads as a vehicle restraint system, particularly in highway construction and temporary traffic management. Can achieve H containment levels when installed in connected runs. Related terms: New Jersey barrier, concrete barrier, vehicle restraint system.

K

Kerb

A concrete, granite, or engineered stone edging element separating road and footway surfaces. Not a vehicle restraint system — standard kerbs are not designed or rated to contain errant vehicles, though a mounted kerb can redirect low-speed vehicles. Related terms: vehicle restraint system, guardrail.

M

Median Barrier

A vehicle restraint system installed in the central reservation (median) of a dual carriageway or motorway to prevent cross-over accidents — vehicles crossing from one carriageway to the other. UK median barriers are specified to BS EN 1317 and the DMRB; concrete barriers are commonly used for median applications as their rigid profile minimises cross-section width. Related terms: central reservation, vehicle restraint system, BS EN 1317.

N

New Jersey Barrier

A synonym for Jersey barrier — a precast concrete barrier with the characteristic New Jersey profile (also called F-shape or NJ profile). The NJ profile is designed to redirect impacting vehicles back into the carriageway while minimising vertical uplift. Related terms: Jersey barrier, concrete barrier, F-shape barrier.

Normalised Acceleration

A measure of the acceleration severity imposed on vehicle occupants during barrier impact, used in BS EN 1317 performance characterisation. The primary indicator is ASI (Acceleration Severity Index) — see separate entry. Related terms: ASI, THIV, BS EN 1317, occupant risk.

O

Occupier's Liability

The legal duty owed by the occupier of premises to visitors (Occupier's Liability Act 1957) and trespassers (Occupier's Liability Act 1984). In the context of barriers and bollards: occupiers must ensure that their safety barriers are fit for purpose, properly maintained, and not a hazard in themselves (e.g., insufficiently visible or poorly anchored). Related terms: maintenance, inspection, duty of care.

P

PAS 68

PAS 68:2013 — UK Publicly Available Specification for vehicle security barriers, published by the British Standards Institution. Impact testing standard for Hostile Vehicle Mitigation products — superseded for new product testing by IWA 14-1 but existing PAS 68 ratings remain valid and widely specified. See IWA 14-1 and HVM. Related terms: IWA 14-1, CTR, HVM.

Performance Class

In BS EN 1317, the performance class (e.g., N2, H1, H2) defines the vehicle type and test conditions against which a VRS has been certified. Selection of the appropriate performance class for a specific application is determined by risk assessment using DMRB CD 377/379. Related terms: containment level, BS EN 1317, DMRB.

Permeability

In crowd management, permeability refers to the degree to which barriers allow people to pass through or under them — relevant to crowd flow management at events. In traffic management, permeability describes whether a barrier allows some vehicle types to pass (e.g., speed cushions are permeable to emergency vehicles that can straddle them). Related terms: crowd control, speed cushion.

Post

The vertical structural member to which guardrail or barrier rail is attached. In Armco barrier systems, posts are typically C-section or circular hollow section (CHS) steel, driven into the ground or bolted to a concrete foundation. Post spacing is typically 2m centres for highway Armco, 2–3m for industrial applications. Related terms: Armco, guardrail, spacer block.

Powder Coating

An electrostatic paint finish applied to steel as a dry powder and cured in an oven. Applied over hot-dip galvanising on safety barriers and bollards to provide colour (RAL) and additional corrosion protection. Standard powder coat thickness: 60–80 microns. Powder coating alone (without galvanising) does not provide adequate long-term corrosion protection for external steel in UK environments. Related terms: RAL, galvanising, corrosion protection.

R

RAL

The European standard colour system (Reichs-Ausschuß für Lieferbedingungen) widely used in the UK for specifying powder coat colours on barriers and bollards. Key RAL codes for safety barriers: RAL 1023 (Traffic Yellow), RAL 3020 (Traffic Red), RAL 5012 (Light Blue), RAL 9005 (Jet Black), RAL 9010 (Pure White). Related terms: powder coating, colour, markings.

Removable Bollard

A bollard system in which the post component can be removed from a permanently installed ground socket using a dedicated key or tool. Allows occasional vehicle access while maintaining security when the post is in position. Socket quality is critical — specify hot-dip galvanised sockets with drainage. Related terms: fixed bollard, telescopic bollard, socket.

S

Safety Fence

A longitudinal Vehicle Restraint System mounted at or near the edge of the carriageway to prevent errant vehicles from leaving the road. Safety fence is a category within BS EN 1317-2 — typically refers to corrugated beam guardrail systems (Armco/W-beam) as distinct from concrete barriers or cable barriers. Related terms: guardrail, Armco, vehicle restraint system.

Softnose Terminal

A proprietary end terminal for W-beam or thrie-beam safety barriers, designed to deform and absorb energy when struck by an impacting vehicle rather than acting as a ramp or spear. Certified to BS EN 1317-4/-7 for highway use. Strongly recommended over turned-down or flared ends where the barrier end is exposed to risk of direct vehicle impact. Related terms: terminal, crash cushion, BS EN 1317-4.

Speed Bump / Speed Hump

A raised section of road surface designed to slow vehicles by inducing vertical movement as they pass over. Speed bumps (shorter, sharper profile) are generally for private land applications; speed humps (longer, gentler sinusoidal profile) are the highway authority's preferred form on adopted roads, governed by the Highways (Road Humps) Regulations 1999. Related terms: speed cushion, Highways (Road Humps) Regulations 1999, traffic calming.

Speed Cushion

A variant of the speed hump in which raised sections leave gaps between the edge of the road and the raised area — allowing emergency vehicles and buses with wide wheelbases to straddle the cushion and pass without significant vertical movement, while still slowing private cars. Governed by the Highways (Road Humps) Regulations 1999 for use on public roads. Related terms: speed bump, speed hump, traffic calming.

Steel Section

The steel profile used in barrier and bollard construction. For bollards: typically circular hollow section (CHS) in diameters of 76mm, 89mm, 114mm, 168mm, or 219mm. For guardrails: W-beam or thrie-beam corrugated profiles. For posts: C-section (channel section) or CHS. Related terms: CHS, W-beam, Armco.

T

Telescopic Bollard

A bollard in which an inner post raises and lowers within a fixed outer sleeve installed in the ground. When raised, presents a full-height bollard; when lowered, the inner post drops below ground level with a flush or low-profile cap covering the sleeve. Provides rapid access control without requiring removal of the post. Related terms: fixed bollard, removable bollard, automatic rising bollard.

Temporary Barrier

A barrier intended for short-term use — typically during roadworks, events, or construction. Temporary barriers include water-filled HDPE barriers, concrete jersey barriers, and Heras fencing. Some temporary barriers are PAS 68 / IWA 14-1 rated for hostile vehicle mitigation applications. Related terms: water-filled barrier, Jersey barrier, Chapter 8.

Terminal

The end treatment of a safety barrier or guardrail run. A properly designed terminal is essential to prevent the open end of the barrier from acting as a ramp or spear in an impact. Options include flared ends, turned-down ends, softnose terminals, and crash cushions. BS EN 1317-4/-7 covers terminal performance requirements for highway use. Related terms: softnose terminal, crash cushion, end terminal.

THIV (Theoretical Head Impact Velocity)

A vehicle occupant injury risk measure used in BS EN 1317 performance characterisation. THIV is the theoretical speed at which an occupant's head would impact the vehicle interior during a barrier strike event — lower THIV means lower head injury risk. Related terms: ASI, normalised acceleration, BS EN 1317.

Traffic Cone

A cone-shaped marker, typically orange or red with white retroreflective bands, used for temporary traffic management. Traffic cones for use on public roads in the UK must comply with BS EN 13422 and Chapter 8. Standard dimensions: 500mm or 750mm height. Related terms: Chapter 8, traffic management.

V

Vehicle Restraint System (VRS)

A system designed to contain or redirect an errant vehicle that has left the intended travel path. VRS includes highway safety fences (guardrails), crash cushions, vehicle parapets on structures, median barriers, and terminals. All highway VRS products in the UK must comply with BS EN 1317. Related terms: BS EN 1317, guardrail, Armco, crash cushion, vehicle parapet.

W

W-Beam

The W-profile (double corrugation) cross-section used in standard Armco crash barrier rail. The W-shape provides the combination of longitudinal flexibility and transverse stiffness that characterises the performance of W-beam guardrail systems. Standard in the UK for highway and industrial safety barrier applications. See also: thrie-beam (a W-beam with an additional corrugation, providing higher containment). Related terms: Armco, guardrail, corrugated beam.

Water-Filled Barrier

A temporary barrier manufactured from HDPE plastic, filled with water to provide ballast and vehicle containment. Lightweight when empty (for transport and storage), heavy when filled (200–400kg per unit). Widely used in UK roadworks (Chapter 8 traffic management) and events. Available in PAS 68 / IWA 14-1 rated variants for HVM applications. Related terms: temporary barrier, PAS 68, Chapter 8, Delta barrier.

Working Width (W)

In BS EN 1317, the working width (W class: W1–W8) defines the maximum lateral space occupied by the VRS and any contained vehicle during an impact event. The working width class is critical for applications where available clearance is limited — such as bridge structures, median barriers with narrow central reservations, or barriers adjacent to footpaths. Related terms: deflection, BS EN 1317, vehicle restraint system.

Y

Yellow Line

A painted road marking. Single yellow lines restrict parking for specified periods (per Traffic Regulation Order); double yellow lines prohibit parking at all times (except for loading/unloading restrictions). Not a physical barrier but often used alongside bollards and guardrail as part of a comprehensive pedestrian safety or traffic management scheme. Related terms: traffic management, Traffic Regulation Order.

Z

Zone of Intrusion

In PAS 68 and IWA 14-1 impact testing, the zone of intrusion is the area on the non-traffic face of the barrier into which any part of the impacting vehicle penetrates during the test. Zero penetration (0.0 intrusion) is the highest security result — the vehicle is fully contained on the traffic-facing side of the barrier. Related terms: PAS 68, IWA 14-1, CTR, penetration.

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