Safe vehicle containment and re-direction is developed through a combination of the flexural resistance of the w-beam guardrail and the bending resistance of the supporting posts.
Upon impact, the posts absorb some of the crash energy through post rotation in the surrounding soil prior to separation from the guardrail as they fully yield. The blocking pieces, positioned between the guardrail and posts, minimise vehicle snagging and reduce the potential for the vehicle to vault over the barrier by maintaining rail height during the initial stages of impact.
Once the guardrail separates from the posts, the rail forms a re-directive ribbon, guiding the vehicle away from the nearby hazard.
Guardrail designs are manufactured in accordance with Australian state road agency designs. Designs vary from state to state. The most common is a w-beam guardrail supported by a c-post and steel blocking piece.
Post spacing varies from state to state. Typically NSW, QLD and SA adopt a post spacing of 2.0m. Victoria has a post spacing of 2.5m.
Straight w-beam guardrail panels can be used when the radius is greater than 45m. When the radius is less than 45m, factory curved guardrail is required.
Posts, blocking pieces and w-beam guardrails are hot dip galvanised.