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Development of Iowa DOT Combination Bridge Separation Barrier with Bicycle Railing – Phase II

REPORT NUMBER

TRP-03-408-20

AUTHORS

Bob Bielenberg, Michael Benson, Scott Rosenbaugh, Ronald Faller, Chaz Ginger, Seok Hwan Yoo, James Holloway

PUBLICATION DATE

2020-07-17

ABSTRACT

A combination bridge rail was designed and crash tested for Iowa Department of Transportation (Iowa DOT) for use alongside a pedestrian/bicycle bridge pathway that would satisfy Manual for Assessing Safety Hardware (MASH) 2016 Test Level 2 (TL-2) criteria. Currently, Iowa DOT employs a combination bridge rail that utilizes a concrete parapet that had previously been successfully evaluated according to National Cooperative Highway Research Program (NCHRP) Report No. 350 TL-4 criteria. While the parapet had been successfully evaluated, the combination bridge rail system as a whole had not been evaluated to any crash test standards. Thus, Iowa DOT desired that researchers at Midwest Roadside Safety Facility (MwRSF) test the new combination bridge separation barrier to current MASH 2016 TL-2 standards to use in place of their current, untested system. The new combination bridge rail system consisted of a pedestrian/bicycle railing mounted atop a vertical concrete parapet. The pedestrian/bicycle railing featured spliced longitudinal rails welded atop structural steel tube posts with welded steel base plates for attachment atop the parapet. In full-scale crash test no. IBBR-1, the 2270P vehicle was successfully redirected, resulting in minimal damage to the rail from plastic deformation and minimal damage to the parapet. This combination bridge rail design minimized the concrete parapet height that could be used in order to safely redirect the impacting vehicle, thus providing many advantages such as reduced dead weight on bridges, decreased construction costs, and improved sight lines.