Key takeaways
- W-beam is a single-wave corrugated section, normally 2.0–4.0 mm galvanised steel, supplied in 4320 mm lengths to EN 1317-2.
- Thrie-beam is the deeper three-wave version used where impact loads are higher, such as bridges and central reserves.
- Bolt pitch and hole position are as important as the profile — the barrier does not align on site if they are wrong.
- Machine cost is high because the material is thick, the station count is high and cutting needs a die-cut press, not a light shear.
What W-beam guardrail is
W-beam guardrail is a corrugated steel section with a single central wave — the cross-section looks like the letter W, hence the name. It is mounted on posts along a road verge so that a vehicle striking it is redirected back toward the carriageway rather than passing through or rebounding into traffic.
The section works by controlled deformation. On impact the wave flattens progressively, absorbing energy over a longer distance and time than a rigid barrier would. That is why the profile geometry is specified precisely and cannot be substituted with a lookalike section — the deformation behaviour is the product.
W-beam guardrail dimensions
A W-beam section is defined by four numbers: the cover width, the profile height, the section length and the bolt hole pitch. The cover width is what the barrier presents to the road once bolted up; the profile height is the depth of the section from the face of the wave to the back of the flanges.
Confusing cover width with the width of the flat strip that goes into the machine is the most common error when specifying tooling. The strip is wider than the finished section because the material is taken up in forming the wave and the flanges — for a 312 mm W-beam, the line is specified with a 490 mm feeding width.
| Dimension | W-beam | What governs it |
|---|---|---|
| Finished cover width | 312 mm | Barrier face presented to the road; fixed by the profile standard |
| Finished profile height | 90 mm | Depth of the section; sets post connection and deflection behaviour |
| Feeding width (strip) | 490 mm | Tooling specification — the flat strip width the line is built to |
| Section length | 4320 mm (EN 1317-2 / AS-NZS) · 3810 mm (ASTM M180) | Road authority specification and post spacing |
| Bolt hole pitch | 800 mm typical | Must match the post spacing and the lap pattern on site |
The standards and what they fix
EN 1317 is the European standard for vehicle restraint systems and governs most of the world outside North America. For W-beam it effectively fixes the section geometry, the output length at 4320 mm, and the bolt hole pitch, commonly 800 mm.
ASTM M180 is the North American equivalent and uses a 3810 mm section length. AS/NZS 3845 applies in Australia and New Zealand, again with a 4320 mm section.
Thrie-beam — a deeper three-wave profile — is used where impact loads are higher: bridges, central reserves, and locations with limited deflection space. It needs different roll tooling but can run on the same base frame as W-beam.
| Standard | Profile | Section length | Main markets |
|---|---|---|---|
| EN 1317-2 | W-beam | 4320 mm | Europe, Middle East, Africa, Asia |
| ASTM M180 | W-beam | 3810 mm | North America |
| AS/NZS 3845 | W-beam | 4320 mm | Australia, New Zealand |
| — | Thrie-beam (three-wave) | 4320 mm | High-risk locations, bridges, central reserves |
Material and coating
Guardrail sections are formed from 2.0–4.0 mm steel, most commonly S235, S275, Q235, Q345 or ASTM A36, with yield strength up to about 345 MPa. Higher-strength steel is used in some specifications but changes the impact behaviour, so it is a design decision rather than a cost-saving one.
Coating is normally hot-dip galvanising to a coating mass specified by the road authority, typically 600 g/m² or more for a 20-plus-year service life. Some specifications use weathering steel, which is left unpainted and forms a stable oxide layer, where maintenance access is difficult.
What this means for the machine
A guardrail line is a genuinely heavy-duty machine and its cost reflects that. Three things drive it. Material thickness of 2–4 mm means rolls, shafts and bearings are far larger than on a roofing line, and the drive is 15–22 kW rather than 7–11 kW. Station count of 16–20 with high roll loads requires a heavier frame. And cutting needs a die-cut press, because a light flying shear cannot cleanly cut 4 mm material at length without distortion.
The inline punch matters more on guardrail than on almost any other product. Bolt positions govern how the sections align on site, so a machine that punches accurately and repeatably is worth more than one that simply forms the profile well.