Report Result

TRP-03-496a-25

Sina Changizian, Cody Stolle, Ronald Faller, Karla Lechtenberg (Polivka), Joshua Steelman

2025-10-02

The Hawaii Department of Transportation’s (HDOT’s) Buried-in-Backslope system was evaluated according to Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) impact conditions. The system consisted of Midwest Guardrail System (MGS) W-beam railing supported by W6x8.5 and W6x9 steel posts and 8-in. deep recycled plastic blockouts, with a lower W-beam rubrail attached to the post. The terminal had a 13:1 flare (4.4 degrees) from a tangent roadside system between post nos. 29 and 10, and a second 7.4:1 flare (6.8 degrees) between post no. 10 and the upstream anchor block. The system passed through a V-ditch with a 120-in. wide, 6H:1V foreslope and a 2:1 backslope. During test no. HBIB-1, conducted according to MASH test designation 3-32, an 1100C passenger car impacted the system 12 in. downstream from the edge of the anchor block. The right-front tire snagged on post nos. 3 through 6, resulting in a longitudinal occupant ridedown acceleration (ORA) of 27.56 g’s. The vehicle’s right A-pillar deformed laterally 4.2 in., which exceeded lateral MASH limit of 3 in. Excessive ORA and A-pillar deformation resulted in test failure. Consequently, the HBIB system was redesigned to reduce the propensity for vehicle snag and excessive A-pillar deformation. The redesigned system followed the ditch profile from post no. 17 through the upstream anchor block, resulting in decreasing system height. Steel tube blockouts were added to the rubrail to mitigate wheel snag. The modified system was successfully retested in test no. HBIB-2. Therefore, test no. HBIB-2 was considered successful. Following the successful test of the redesigned buried-in-backslope system, the remaining required full-scale crash tests, test designation nos. 3-33, 3-34, and 3-35, run as test nos. HBIB-3 through HBIB-5, respectively, were conducted and all satisfied MASH TL-3 safety criteria. This report describes standard direction testing to MASH criteria, while a second report describes reverse-direction testing.

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

TRP-03-496a-25.pdf