Phase III Demonstration of Ponderosa Pine Round Posts as Alternative to Rectangular SYP Posts in G4(2W) Guardrail Systems
Karla Lechtenberg, Ronald Faller, Scott Rosenbaugh, John Reid
Previously, researchers at the Midwest Roadside Safety Facility (MwRSF) utilized dynamic bogie testing to determine the appropriate diameter, length, and embedment depth for Ponderosa Pine (PP) posts used as a surrogate for 6-in. x 8-in. (152-mm x 203-mm) rectangular Southern Yellow Pine (SYP) posts found in existing, strong-post, G4(2W) W-beam guardrail systems. More specifically, a PP post with an 8½-in. (216-mm) ground line diameter, a 35-in. (889-mm) embedment depth, and a 64-in. (1,626-mm) post length, was recommended as a surrogate in existing Arizona G4(2W) guardrail systems. Further, a PP post with an 8⅝-in. (219-mm) ground line diameter, a 36-in. (914-mm) embedment depth, and a 65-in. (1,651-mm) post length, was recommended as a surrogate in existing U.S. standard G4(2W) guardrail systems. The research conducted herein further demonstrated that the two noted PP post sizes and configurations provided adequate safety performance according the Test Level 3 (TL-3) impact safety standards published in the National Cooperative Highway Research Program (NCHRP) Report No. 350. One full scale vehicle crash test was successfully performed on a 175-ft (53.34-m) long, G4(2W) guardrail system supported by 8½-in. (216-mm) diameter (ground line) by 64-in. (1,626-mm) long PP posts with a 35-in. (889-mm) embedment depth. The test was conducted with a ¾-ton Chevrolet pickup truck (2000P vehicle) impacting at a speed of 60.7 mph (97.7 km/h) and an angle of 24.8 degrees. The G4(2W) guardrail system with PP posts adequately contained and redirected the pickup truck and met the TL-3 safety performance criteria. Therefore, an 8½-in. (216-mm) diameter PP post with a 35-in. (889-mm) embedment depth and a 64-in. (1,626-mm) ength was further confirmed for use as a surrogate in existing Arizona G4(2W) guardrail systems based on dynamic component testing and full-scale vehicle crash testing. Based on similarities between the two PP posts and prior successful dynamic component testing, an 8⅝-in. (219-mm) diameter PP post with a 36-in. (914-mm) embedment depth and a 65-in. (1,651-mm) length was also recommended for use as a surrogate in existing U.S. standard G4(2W) guardrail systems.
Highway Safety, Roadside Safety, Crash Test, Roadside Appurtenances, Compliance Test, NCHRP Report No. 350, Wood Post, Round Post, Ponderosa Pine, W-Beam Guardrail, Longitudinal Barrier, G4(2W), Equivalency