Performance of Longitudinal Barriers on Curved, Superelevated Roadway Sections (2019) / Chapter Skim
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1 S U M M A R Y Performance of Longitudinal Barriers on Curved, Superelevated Roadway Sections Background and Objectives NCHRP Project 22-29, "Performance of Longitudinal Barriers on Curved, Superelevated Roadway Sections," and Project 22-29A, "Evaluating the Performance of Longitudinal Barriers on Curved, Superelevated Roadway Sections," were initiated to develop a better understanding of the safety performance (i.e., crashworthiness) for barriers used on curved, superelevated roadway sections (CSRS)
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2 of a vehicle at its interface with varying barrier types and their placement. The underlying premise for these analyses was that a good vehicle-to-barrier interface is necessary for adequate safety performance.
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3 The research considered variations in shoulder width and slopes and organized the results based on shoulder angle as noted in Figure 2. This metric reflects the cross section slope changes on the superelevated roadway to the adjacent shoulder.
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4 and CarSim (CarSim 2006) programs for VDA were used to generate vehicle trajectories to gain insights on the influences of surface features on the orientation of the vehicle and the likely barrier interface regions for the various superelevation, slope, shoulder, and backslope conditions.
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5 Tabular summaries were also generated of the interface performance for all the specific conditions of interest. The plots and tabular summaries reflect the physics of a vehicle leaving the road on a CSRS and interfacing with barriers positioned at edge of the shoulder.
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Note: Values in red type indicate situations where poor interface conditions are likely to exist. Table 2.
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7 The vehicle approaches as if from the inside travel lane on a departure trajectory. The simulation is initiated away from the barrier to allow the vehicle model to be "stabilized" before impact.
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8 and a 4-ft-wide shoulder with an 8% shoulder angle. The barriers were oriented normal to road.
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9 Note: Asterisk (*
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10 of impacts with the NJ concrete barrier indicated that it is more prone to fail the crashworthiness requirements for situations where the superelevation is 8% or greater and the shoulder angle is 6% to 8%. • Performance under less severe CSRS and barrier placement conditions is incrementally improved.
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11 Development of Guidance for Deployment of Longitudinal Barriers on CSRS A considerable amount of information was derived from the VDA, simulation analyses, and crash testing. The challenge was to translate these results into guidance for the design, selection, and installation of longitudinal barriers on CSRS.
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12 These are subject to further vetting, rewording, and editing in consultation with AASHTO committees. This construct provides a summary of the findings of the multifaceted analyses that support the proposed guidance for barrier design, selection, and installation.
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13 • The results indicated that there was some potential for failure, but options for addressing the problems existed. • Three full-scale crash tests were conducted that validated the simulation analyses.
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