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Minimum Effective Guardrail Length For The MGS




Nick Weiland, John Reid, Ronald Faller, Dean Sicking, Bob Bielenberg, Karla Lechtenberg (Polivka)




Varying roadside hazards and roadway geometries can result in a calculated length-of-need for a W-beam guardrail system to be shorter than the currently-tested minimum length. The recommended minimum length for the standard Midwest Guardrail System (MGS) has been 175 ft (55.3 m) based on crash testing according to the NCHRP Report No. 350 and MASH testing specifications. The primary objective of this research study was to evaluate the effects of reducing the system length of the MGS. The research study included one full-scale crash test with a Dodge Ram pickup truck impacting a 75-ft (22.9-m) long MGS system. The 75-ft (22.9-m) long system satisfied the MASH Test Level 3 (TL-3) evaluation criteria for test designation no. 3-11. A comparison of the 75-ft (22.9-m) and 175-ft (55.3-m) long systems demonstrated that the reduced system length did not adversely affect the overall system performance or deflections. A detailed analysis was then performed using BARRIER VII and LS-DYNA to analyze system performance with lengths of 62 ft - 6 in. (19.1 m) and 50 ft (15.2 m). The 62-ft 6-in. (19.1-m) MGS produced similar rail forces, deflections, anchor forces, and anchor deflections as the 75-ft (22.9-m) MGS. The 50-ft (15.2-m) and 62-ft 6-in. (19.1-m) MGS systems indicated successful redirection of the vehicle and shielding of the hazard. However, full-scale crash testing is recommended for both the 62-ft 6-in. (19.1-m) and 50-ft (15.2-m) MGS. This research was conducted to evaluate the strength of the shortened MGS system and not to recommend real world installations of the MGS at these reduced lengths.


Highway Safety, Crash Test, Roadside Appurtenances, Compliance Test, MASH, MGS, Guardrail, TL-3, Minimum Length

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