Development of Iowa Dot Combination Bridge Separation Barrier with Bicycle Railing

The Iowa Department of Transportation typically builds separation barriers between vehicle and pedestrian/bicycle facilities when sidewalks or trails are present on vehicular bridges. Currently, Iowa DOT employs a combination bridge rail that utilizes a concrete parapet that previously had been successfully evaluated to National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 4 (TL-4) criteria for these situations. While the parapet had been successfully evaluated, the combination bridge rail system as a whole had not been evaluated to any crash test standards. Iowa DOT desired that researchers at Midwest Roadside Safety Facility (MwRSF) design and test a combination bridge separation barrier to current Manual for Assessing Safety Hardware (MASH) TL-2 standards to use in place of their current, untested system. During this effort, previous combination rails, low-height vertical parapets, and zone of intrusion (ZOI) studies were reviewed to provide guidance on system design. A simulation effort was also performed to aid in height selection of the parapet, as well as placement of the attached bicycle rail to reduce the amount of negative vehicle-to-rail interaction with the system. Using the information gathered during the review of previous systems and simulation effort, a full system design was produced. It was then recommended that the proposed system be evaluated to MASH test designation 2-11 in order to assess the system’s performance during a vehicle impact scenario. Advisor: John D. Rei