Key takeaways
- EN 1317 classifies guardrail by containment level (N2, H1, H2...) and working width — the whole system must be tested, not just the section.
- Standard section length is 4320 mm (EN 1317, AS/NZS) or 3810 mm (ASTM M180).
- Bolt hole pitch of 800 mm is standard under EN 1317 — incorrect hole position prevents site assembly.
- Hot-dip galvanising to ISO 1461 is the standard corrosion protection; minimum 45 µm average for 3 mm sections.
- Lap direction must be set so vehicle impact forces the lap closed — sections must be installed in the correct traffic-direction order.
Why guardrail must be specified, not just ordered
Highway guardrail is a safety-critical product. A guardrail section that does not meet the specified profile geometry, section length, bolt hole pitch or material strength will not align correctly on site and may not perform as designed in a vehicle impact. Road authorities and highway contractors require documentation — mill certificates, dimensional inspection reports, and usually a CE mark or equivalent — before accepting a guardrail delivery.
Specifying correctly means identifying: the applicable standard (which fixes the geometry and testing requirements), the section length, the material and coating, the bolt hole pattern, and the required impact performance class. This page covers each in order.
Standards and impact performance classes
EN 1317 is the European standard for vehicle restraint systems and is the reference standard for most of the world outside North America. Under EN 1317-2, guardrail systems are classified by containment level (N2, H1, H2, H3, H4b) and working width class (W1–W8). W-beam guardrail is typically tested to N2 containment.
ASTM M180 is the North American standard. It specifies the section geometry and mechanical properties for W-beam sections but does not include a vehicle impact test class in the same way as EN 1317. Road authorities in the US and Canada have their own approval requirements based on NCHRP and AASHTO test protocols.
AS/NZS 3845 applies in Australia and New Zealand, referencing EN 1317 test protocols but with local geometric specifications.
If the project specification calls for a particular containment class (for example N2 W4 under EN 1317-2), the guardrail system — posts, sections, end treatments and fixings together — must have been tested as a system to that class. An individual section with the correct geometry does not by itself constitute compliance unless it is part of a tested and certified system.
| Standard | Market | Key requirement | Length |
|---|---|---|---|
| EN 1317-2 | Europe, Middle East, Africa, Asia | Containment class N2, H1, H2... | 4320 mm |
| ASTM M180 | United States, Canada | Section geometry and tensile strength | 3810 mm |
| AS/NZS 3845 | Australia, New Zealand | EN 1317 protocols, local geometry | 4320 mm |
Material and coating specification
W-beam guardrail sections are produced from 2.0–4.0 mm steel, most commonly 3.0 mm. Standard material grades are S235, S275, Q235 or Q345 (yield strength up to 345 MPa). High-containment sections may specify higher-strength steel; confirm with the testing certification.
Hot-dip galvanising to ISO 1461 is the standard corrosion protection for guardrail. The minimum average zinc coating is 45 µm for sections up to 3 mm and 55 µm for thicker material. Road authorities in aggressive environments (coastal or de-icing salt) may require 85 µm or duplex coating (zinc plus paint).
Alternative coatings: electro-galvanised sections (much thinner zinc, not suitable for outdoor highway use), zinc-rich primer plus paint (used for repair sections in some markets), and bare weathering steel (Corten — used in a minority of highway authority specifications where aesthetics are important).
Bolt hole pattern and section dimensions
The bolt hole pitch on a W-beam section is typically 800 mm under EN 1317-2 — the holes must align between adjacent lapping sections and with the post spacings. The hole diameter, edge distance and hole position must match the specification precisely. A section with the correct profile but incorrect hole positioning will not assemble correctly on site.
Section length: 4320 mm is the standard under EN 1317 and AS/NZS. ASTM M180 uses 3810 mm. Custom lengths are sometimes produced for specific applications (bridge ends, end treatments) but require separate confirmation of the hole pattern and lap arrangement.
The lap: adjacent sections overlap by approximately 320 mm (one bolt spacing) at each end. The overlap direction is set so that vehicle impact forces the lap tight rather than opening it — sections must be installed in the correct direction relative to traffic flow.
Documentation required for delivery
Most road authority specifications require: a mill certificate for the steel coil confirming grade and mechanical properties; a hot-dip galvanising test report confirming coating thickness; a dimensional inspection report confirming profile geometry and hole positions against the standard; and, for European markets, a CE marking declaration referencing the relevant harmonised standard.
For systems sold into EN 1317 markets, the CE marking applies to the system, not the individual section. The system supplier (not the section manufacturer) is responsible for the system CE declaration and the supporting European Technical Assessment (ETA) or test report.