Plain-language explanations of road restraint systems, the EN 1317 classification and how to choose and install a steel guardrail.
EN 1317 glossary
How heavy and fast a vehicle the barrier is proven to contain. EN 1317 groups levels into normal (N1–N2), higher (H1–H3) and very high (H4a–H4b) containment.
The maximum lateral space the barrier occupies during the crash test. W1 is ≤ 0.6 m and W8 is ≤ 3.5 m; it tells designers how much clear space is needed behind the barrier.
A measure of how violently occupants are decelerated. Class A is gentler than class B, so A is preferred where space allows.
A steel rail with a “W”-shaped cross-section, bolted through spacers to posts. It bends and stretches to absorb energy and guide the vehicle.
Immersing finished steel parts in molten zinc to form a bonded coating that protects against corrosion for decades.
Iran’s national standard for single-sided W-beam safety barriers, used for the Persian Guardrail.
Guides
Short answers drawn from our engineering team’s field experience. For a project-specific recommendation, send us your road details.
A steel W-beam guardrail deflects and absorbs energy, so it needs working width behind it but is lighter, faster to install and easier to repair. A concrete New Jersey barrier is rigid and needs almost no working width, but it is heavier and transmits more force to the vehicle. Steel guardrail is the usual choice for roadsides; rigid barriers suit narrow medians and work zones.
A two-wave (W-beam) rail has two corrugations and suits normal containment. A three-wave (thrie-beam) rail is deeper, stiffer and used where higher containment or heavier vehicles are expected, such as bridges and high-risk curves.
Start from the traffic mix, design speed and the hazard behind the barrier. Normal containment (N2) suits most roadsides; H1–H2 is used where heavy vehicles or severe hazards exist; H4b is reserved for very high-risk sections such as bridges over railways or rivers.
Posts are driven or set at the spacing of the tested system (for example every 1.33, 2.0 or 4.0 m), spacers are bolted to the posts, and W-beams are lapped in the direction of traffic and bolted. Ends must be anchored or fitted with tested end terminals.
Hot-dip galvanized steel resists corrosion for decades in most climates. Lifetime depends on the environment — coastal and de-icing-salt conditions are the most demanding — and damaged sections are replaced individually.
Structural steels S235JR and S355JR to EN 10025, with W-beam thicknesses of 2.67, 3.00 or 3.43 mm depending on the system.
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