Thrie-beam Guardrail provides a higher level of performance for retaining larger vehicles. The AASHTO G9 system is “deemed to comply” to NCHRP Test Level 3 in the standard block configuration and Test Level 4 in the modified block configuration.
Thrie-beam Guardrail has a larger profile, and is better suited to protecting motorists from hazards that are in close proximity to the road verge. It sits higher than traditional W-Beam barrier and provides superior performance in its ability to retain vehicles with a higher centre of gravity.
Transitions from W-Beam to Thrie-beam Guardrail are used on bridge approaches to ensure an effective transition from a semi-rigid to rigid barrier. Thrie-beam’s stiffness ensures reduced deflections in these locations and hence minimises the likelihood of vehicle “pocketing”.