Title

Performance of Steel-Post, W-Beam Guardrail Systems

Document Type

Journal Article

Publication Date

2007

Subject Area

operations - performance, planning - safety/accidents, organisation - performance, mode - rail

Keywords

W-beam guardrail, W beams, Steel posts, Road safety, Pickup trucks, Performance, NCHRP Report 350, Impact tests, Highway safety, Guiderails, Guardrails, Guard rails, Guard fences, Crash tests, Collision tests

Abstract

On the basis of the proposed changes to the NCHRP Report 350 guidelines, NCHRP Project 22-14(2) researchers deemed it appropriate to first evaluate two strong-post W-beam guardrail systems before finalizing the new crash testing procedures and guidelines. For this effort, the modified G4(1S) W-beam guardrail system and the Midwest Guardrail System (MGS) were selected for evaluation and comparison. Five full-scale vehicle crash tests were performed with the two longitudinal barrier systems, in accordance with the Test Level 3 (TL-3) requirements presented in the NCHRP Report 350 Update. For the modified G4(1S) testing program, two 2,270-kg pickup truck vehicles (2270P vehicles) were used: one ¾-ton, two-door vehicle and one ½-ton, four-door vehicle. For the MGS testing program, two 2,270-kg pickup truck vehicles (2270P vehicles) and one 1,100-kg small-car vehicle (an 1100C vehicle) were used, with both pickup truck configurations being evaluated. On the basis of several findings, the NCHRP Project 22-14(2) researchers determined that the ½-ton, four-door pickup truck was better suited for use as a surrogate light truck test vehicle than the ¾-ton, two-door pickup truck. The modified G4(1S) W-beam guardrail system, mounted at the top rail height of 706 mm, provided acceptable safety performance when it was crashed into by the ½-ton, four-door pickup truck vehicle, thus meeting the proposed TL-3 requirements presented in the NCHRP Report 350 Update. Testing of the modified G4(1S) W-beam guardrail system was not successful with a ¾-ton, two-door pickup truck under the TL-3 impact conditions. The MGS was found to meet the TL-3 criteria presented in the NCHRP Report 350 Update for Test Designations 3-10 and 3-11. Satisfactory safety performance was observed with the MGS with both the ½-ton, four-door and ¾-ton, two-door pickup truck vehicles.