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Crash Testing and Evaluation of the Hawaii Thrie Beam Approach Guardrail Transition: MASH Test Nos. 3-20 and 3-21




Erin Urbank, Ronald Faller, Sam Hovde, Scott Rosenbaugh




The Hawaii Department of Transportation’s (HDOT’s) Thrie Beam Approach Guardrail Transition (AGT) was designed to safely transition from W-beam guardrail to a rigid concrete parapet. However, the AGT had not yet been evaluated under the current safety standards of the American Association of State Highway and Transportation Official (AASHTO) Manual for Assessing Safety Hardware, 2nd Edition (MASH 2016). The AGT consisted of nested thrie beam supported by W6x15 and W6x9/W6x8.5 steel posts and was attached to HDOT’s specially-designed reinforced concrete end post, the Type D2 End Post. The AGT was also designed for use with a vertical 6-in. curb placed below the thrie beam. Although not originally part of HDOT’s AGT design, the upstream section was modified to include the MGS stiffness transition utilizing an asymmetrical W-to-thrie transition segment to ensure a crashworthy connection between the upstream W-beam and the downstream nested thrie beam. Within this research study, two full-scale crash tests were conducted on the HDOT AGT to investigate the safety performance according to Test Level 3 (TL-3) criteria in MASH 2016. Test nos. HWTT-1 and HWTT-2 were conducted in accordance with MASH 2016 test designation nos. 3-20 and 3-21, respectively. In both tests, the transition successfully contained and safely redirected the vehicles. All occupant risk measurements were found to be within the established MASH 2016 limits. Therefore, test nos. HWTT-1 and HWTT-2 were deemed to have satisfied all safety performance criteria, and the modified HDOT thrie beam AGT to concrete parapet was determined to be crashworthy to MASH 2016 TL-3.


Highway Safety, Crash Test, Roadside Appurtenances, Compliance Test, MASH 2016, Approach Guardrail Transition, AGT, Concrete Parapet, Thrie Beam

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