Research Article Transportation Research Record 1–11 Ó National Academy of Sciences: Transportation Research Board 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0361198120921168 journals.sagepub.com/home/trr Crash Testing and Evaluation of Culvert- Mounted Midwest Guardrail System Mojdeh Asadollahi Pajouh 1 , Robert W. Bielenberg 1 , Jennifer D. Schmidt-Rasmussen 1 , and Ronald K. Faller 1 Abstract Concrete box culverts are usually installed under roadways to allow water drainage without affecting the motoring public. Culvert openings can represent a hazard on the roadside when they do not extend outside of the clear zone, and often require safety treatments in the form of roadside barriers. In this study, a modified design of Midwest Guardrail System (MGS) was evaluated for installation on a low-fill culvert with the strong-post attachment using through-bolts and epoxy anchorage through full-scale crash testing. The test installation consisted of MGS with a 31 in. top rail height, supported by W6 3 9 posts, spaced at 37½in., attached to a low-fill culvert’s top slab with a 12 in. offset from the back of the post to the culvert headwall. Two crash tests were conducted according to the American Association of State Highway and Transportation Officials’ (AASHTO) Manual for Assessing Safety Hardware (MASH) 2016 Test Level 3 impact safety criteria. In test number CMGS-1, a 2,428-lb car impacted the MGS attached to the culvert at a speed of 61.3mph and at an angle of 25.1°. In test number CMGS-2, a 5,013-lb pickup truck impacted the MGS attached to the culvert at a speed of 62.8mph and an angle of 25.7°. In both tests, the vehicle was safely redirected and captured. Both tests were deemed acceptable according to TL-3 safety criteria in MASH. Recommendations were made for the safe installation of MGS atop low-fill culverts as well as transitions from the standard MGS to the culvert-mounted MGS. Concrete box culverts are routinely installed under road- ways to allow water drainage without affecting the motoring public. Unfortunately, box culverts can repre- sent a hazard on the roadside when they do not extend outside of the clear zone. For major drainage structures, such as concrete box culverts, an appropriate traffic bar- rier is often the most effective way to prevent errant vehi- cles from running off the edge of the culvert. The most common safety barriers utilized to shield these areas are W-beam guardrail systems. However, low-fill culverts with less than 40 in. (1,016 mm) of soil fill prevent the proper installation of standard guardrail posts because of a lack of available embedment depth. Previous crash testing has shown that in some cases W-beam installa- tions with shallow post embedment do not perform ade- quately and are prone to vehicle override (1). Therefore, low-fill culverts require specialized guardrail systems to safely treat the hazard. Currently, three different types of guardrail systems are being used to treat cross-drainage box culverts: (1) long-span guardrail systems; (2) guard- rail systems anchored to the top slab of the culvert; and (3) guardrail systems anchored to the culvert headwall. Long-span guardrail systems contain unsupported lengths of W-beam rail that span over the top of culverts. These barrier systems do not require attachment to the culvert, thus allowing the culvert and the barrier system to operate independently. One Manual for Assessing Safety Hardware (MASH)-compliant long-span system, developed at the Midwest Roadside Safety Facility (MwRSF), consisted of a single layer of 12-gauge (2.66 mm thick), 31 in. (787 mm) tall W-beam guardrail cen- tered over a 25 ft (7.6 m) unsupported span length (2, 3). The long-span systems do not require additional compo- nents for attachment to the culvert and provide a cost- effective method for shielding culverts. However, these long-span systems are limited to a maximum unsup- ported span length of 25 ft (7.6 m). For low-fill culverts of widths exceeding the maximum unsupported length of long-span systems, a few W-beam guardrail designs are available for direct attachment to the culvert’s top slab. One such guardrail system was developed in 2002 by MwRSF, as shown in Figure 1a 1 Midwest Roadside Safety Facility, University of Nebraska-Lincoln, Lincoln, Nebraska, NE Corresponding Author: Mojdeh Asadollahi Pajouh, mojdeh.pajouh@unl.edu