Report Result

TRP-03-478b-25

Scott Rosenbaugh, Mojdeh Pajouh, Ethan Galusha, Ronald Faller

2025-07-15

The Hawaii Department of Transportation (HDOT) has utilized bridge railings similar to the Hawaii Modified Natchez Trace Bridge Rail to safely redirect vehicles on bridges. However, the crashworthiness of this bridge rail had not been investigated under current impact safety standards, the Manual for Assessing Safety Hardware (MASH). Previously within this project, crash test no. HNTBR-1 was conducted on this railing according to MASH test designation no. 3-11. In this test, the occupant compartment intrusion at the wheel well and toe pan measured 12.7 in., which exceeded the MASH limit of 9 in. Thus, test no. HNTBR-1 failed to meet MASH safety criteria. An investigation into the cause of this test failure was conducted. The failure was attributed to two key causes: (1) a reduced curb-to-rail offset, which caused the vehicle rim to gouge into the concrete rail while the wheel was traversing over the curb, and (2) the angled bottom edge of the rail which increased the severity of the rim-rail snag. Design modifications were proposed and discussed with HDOT. The selected modifications included changing the shape the bridge rail to a vertical front face for the both the railing and the lower curb. This shape change would minimize wheel climb and reduce snagging at the rail’s bottom edge. Reinforcement of the rail and curb was adjusted accordingly. Two full-scale crash tests were conducted to evaluate the safety performance of the new Hawaii Concrete Post and Beam Bridge Rail. Test nos. HNTBR-2 and HNTBR-3 were conducted according to MASH test designation nos. 3-11 and 3-10, respectively. In both tests, the vehicles were safely contained and redirected with minimal damage to the bridge rail. All occupant risk measurements were found to be within the established MASH limits, including the occupant compartment deformations that had been an issue with the previous design configuration. Therefore, test nos. HNTBR-2 and HNTBR-3 satisfied all safety performance criteria, and the Hawaii Concrete Post and Beam Bridge Rail was determined to be crashworthy according to MASH TL-3.

Highway Safety, Crash Test, Roadside Appurtenances, Bridge Rail, Compliance Test, MASH, Test Level 3, Revised Design Modified Natchez Trace Bridge Rail

TRP-03-478b-25.pdf