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ABSTRACT

This report documents four full-scale crash tests conducted to evaluate the safety performance of the Hawaii Department of Transportation’s (HDOT’s) Thrie-Beam Approach Guardrail Transition (AGT) according to the Manual for Assessing Safety Hardware, Second Edition (MASH 2016) Test Level 3 (TL-3) crash test criteria. This HDOT AGT consisted of 12.5 ft of nested thrie-beam rail and 6.25 ft of single ply thrie beam rail supported by W6x15 and W6x8.5 steel posts. The downstream end of the AGT was attached directly to the Hawaii Modified Delaware Retrofit Thrie-Beam Bridge Rail at the first bridge rail post. Below the AGT, a 6-in. tall concrete curb was placed flush with the front of the thrie beam rail. The curb’s height transitioned up to meet the height of the elevated sidewalk on the bridge. Test no. HMDT-1 was conducted in accordance with MASH test 3-21. In test no. HMDT-1, the transition contained and redirected the vehicle; however, the maximum allowable intrusion limits for the wheel well and toe pan area violated the MASH limits. Thus, test no. HMDT-1 was deemed unacceptable. Modifications were incorporated into the AGT design to mitigate the vehicle snag and excessive toe pan deformations. The vertical slope for the curb was flattened from 3H:1V to 6H:1V, and the AGT was stiffened by reducing the post spacing adjacent to the bridge rail end from 37½ in. to 18¾ in. Two full-scale crash tests, test nos. HMDT-2 and HMDT-3, were conducted on this modified AGT in accordance with MASH test designation nos. 3-21 and 3-20, respectively. Test no. HMDT-2 was deemed to have satisfied all safety performance criteria. In test no. HMDT-3, the transition redirected the vehicle; however, the maximum allowable intrusion limits for the side front panel area violated the MASH limits. Thus, test no. HMDT-3 was deemed unacceptable. Again, modifications were applied to the AGT, and the rail adjacent to the bridge rail was stiffened by adding a steel plate to the back side of the rail. In test no. HMDT-4, the AGT successfully contained and safely redirected the test vehicle. Test nos. HMDT-2 and HMDT-4 were deemed to have satisfied all safety performance criteria. Thus, the AGT to Hawaii Modified Delaware Thrie-Beam Bridge Rail installed behind and above a 6-in. tall curb was determined to be crashworthy according to MASH 2016 TL-3.

KEYWORDS

Highway Safety, Crash Test, Roadside Appurtenances, Compliance Test, MASH 2016, Test Level 3, Approach Guardrail Transition, AGT, Modified Delaware Retrofit Thrie-Beam Bridge Rail, Curb

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