Safety Performance Evaluation of G4(2W) W-Beam Guardrail with Blockouts Raised by 3” Background

Background Barriers are designed and tested to specific design parameters and variations from the design requirements can influence their performance. For this reason, there are tolerances set for the installation and maintenance of w-beam guardrails. These installation guidelines call for a rail height of 27.5 inches plus or minus 3 inches. Despite the efforts to comply with the guidelines, a myriad of factors pose challenges to keeping barriers at the designated height. Factors that influence the effective height of a guardrail include incorrect installation, ground settlement, damage from nuisance hits, and roadway resurfacing. Recent research has shown that guardrails even an inch lower than the guideline height result in a greater propensity for vaulting by the larger vehicles on the road (e.g., 2000 kg pick-up trucks) [1].