Development of the Midwest Guardrail System (MGS) for Standard and Reduced Post Spacing and in combination with curbs
Karla Lechtenberg (Polivka), Ronald Faller, Dean Sicking, John Reid, John Rohde, Jim Holloway, Bob Bielenberg, Beau Kuipers
A new strong-post W-beam guardrail system called the Midwest Guardrail System (MGS) was developed, testing, evaluated, and provides increased safety for impacts with higher center-of-mass vehicles. The new barrier utilizes W-beam guardrail and standard W6x9 steel posts. Design differences between the MGS and standard W-beam systems include a new W-beam guardrail and standard W6x9 steel posts. Design differences between the MGS and standard W-beam systems include a new W-beam rail top mounting height of 787 mm (31 in.), a reduced guardrail post embedment depth, an increased blockout depth from 203 mm (8 in.) to 305 mm (12 in.), and a repositioning of the guardrail splice from a post to a midspan location. Additional design variations of the new MGS included a standard guardrail design configured with a 152-mm (6-in.) high concrete curb as well as stiffened versions using reduced (half and quarter) post spacings. All six full-scale vehicle crash tests were conducted and reported in accordance with the Test Level 3 (TL-3) requirements specified in the National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. One of the full-scale crash tests was conducted to verify that the guardrail performs adaquately with mini-size automobiles when raised to an 813 mm (32 in.) top mounting heights. This test proved that the barrier can provide satisfactory performance when mounted at heights ranging from standard guardrail height of 706 mm (27.78 in.) to 813 mm (32 in.). Hence, the safety performance of the Midwest Guardrail System (MGS) was determined to be acceptable according to the TL-3 evaluation criteria specified in NCHRP Report No. 350 and provides approximately 107 mm (4.2 in.) of mounting height tolerance. The research study also included computer simulation modeling with LS-DYNA to study guardrail design parameters, dynamic bogie testing on steel posts placed at various embedment depths and computer simulation modeling with BARRIER VII to analyze and predict dynamic guardrail performance. Recommendations for the placement of the original Midwest Guardrail System (MGS) as well as its stiffened variations were also made.
Highway Safety, Roadside Appurtenances, Longitudinal Barriers, Guardrail, Guardrail Placement, Guardrail Stiffening, Curbs, Crash Test, Compliance Test, Computer Simulation
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