Evaluation of the Hawaii Modified Delaware Retrofit Thrie-Beam Bridge Railing and Approach Guardrail Transition

The Hawaii Department of Transportation (HDOT) utilizes the Hawaii Modified Delaware Retrofit Thrie-Beam Bridge Rail to safely redirect vehicles on bridges with elevated sidewalks. However, the crashworthiness of this bridge rail has not been investigated under current impact safety standards. This bridge rail consists of a 10-gauge thrie-beam rail supported by W6x25 steel posts spaced at 6 ft 3 in. on-center. The top-mounted posts are anchored to an elevated concrete sidewalk ranging in height from 6 in. to 9 in. The ends of the bridge rail are connected to thrie-beam approach guardrail transitions (AGTs), which were designed to safely transition from a more flexible W-beam guardrail to the stiffer thrie-beam bridge rail. The objective of this research was to evaluate the Hawaii Modified Delaware Retrofit Thrie-Beam Bridge Rail and its associated AGT through full-scale crash testing in accordance with AASHTO’s Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) safety criteria. Three crash tests were conducted on the bridge rail, including tests on both the 6 in.- and 9 in.-tall sidewalk configurations. Four crash tests were conducted on the AGT, two of which resulted in excessive occupant compartment deformations that required design modifications and retesting. This paper details the crash test evaluations of both the bridge rail and AGT, the modifications made to the AGT to satisfy MASH TL-3 safety criteria, and recommendations for implementation of the system.