Curved, high-speed roadways are usually superelevated in order to make the curved roadway easier for vehicles to navigate. Since curved roadside barriers would be expected to produce higher impact angles and therefore a greater potential for occupant injury, there is a possibility that curvature could degrade the performance of a barrier. An increase in the impact angle can cause an increase in impact loading that could potentially exceed the structural capacity of a barrier and result in vehicle penetration or override of the barrier. Therefore, NCHRP Project 22-29 was undertaken to study them in order to quantify the performance of longitudinal barriers on superelevated, curved roadways. The NCHRP Project 22-29 research team’s review of the literature, analyses of accident data, and surveys of the state DOTs did not suggest a safety problem with barriers on curved, superelevated sections. However, the research team thought it prudent to validate these findings through computer simulations and crash testing. Since the surveys showed that the state DOTs planned to use G4-1S and MGS guardrails, vertical concrete walls, and NJ- and F-shape barriers on curved roadways in the near future, the simulations and crash testing should emphasize these barrier types. The researchers also obtained information from the state DOTs about the details of superelevation designs that will be used on high-speed highways. The researchers used vehicle kinematics models to study the trajectories of vehicles traversing various superelevated sections and impacting barriers. Finite element models of vehicles were validated. Finite element models were made of guardrails and concrete barriers and then converted to curved barriers using a new computer program written for that purpose. However, due to organizational changes, NCHRP Project 22-29 was not completed, and this follow-on study is intended to finish that research.
The objectives of this research are to (1) evaluate the crash performance of standard longitudinal barriers installed on superelevated, curved roadways; (2) determine if the curvature and superelevation details used by the state DOTs degrade the performance of the barriers to the extent that they will no longer meet the crash test criteria for MASH TL-3; and (3) develop a plan for possible future research to study barrier modifications, changes to roadway geometrics, or both, in response to any identified problems.
This research shall complete work begun under NCHRP Project 22-29, "Performance of Longitudinal Barriers on Curved, Superelevated Roadway Sections." In addition to the evaluation of crash performance, it shall include (1) a review of development and validation of the crash simulations in Project 22-29 using LS-DYNA finite element models of five vehicles and three barrier types (G4-1S, MGS and vertical concrete) and (2) completion of one planned simulation left undone in Project 22-29. Since performing high-speed crash testing on a superelevated section presents significant physical challenges, the proposal shall address in detail (1) how the vehicle will be propelled and directed into the barrier, (2) how the superelevated section will be constructed, and (3) the recommended geometry for each proposed crash test.
(1). Review the simulation analyses developed in NCHRP Project 22-29 and identify parameters critically affecting the safety performance of longitudinal barriers placed on curved, superelevated roadway sections. Use LS-DYNA modeling to evaluate the performance of the selected barrier types (G4-1S, MGS, and vertical concrete) under MASH TL-3 impact conditions and conduct any further analyses and simulations needed to fill gaps in the results.(2). Submit a work plan for MASH TL-3 crash testing of selected guardrails and vertical concrete barriers placed on curved, superelevated roadway sections. The work plan shall provide a brief explanation of why each test was selected and what the researchers hope to learn from the test. (3). Conduct the crash tests. Compare the results of the crash tests to the simulation results. If the crash test results significantly differ from the simulation results, conduct additional simulations to try to identify the sources of the differences. (4). Use the computer simulations and crash test results as the basis for development of proposed guidance for the design, selection, and installation of the MASH TL-3 longitudinal barriers that will be used by the state DOTs on curved, superelevated roadway sections.(5). Prepare (1) a final report that presents the results, findings, and conclusions of the research and (2) a 5- to 10-page executive summary of the final report. The final report shall include the following: (1) The results of the crash tests of the longitudinal barriers evaluated in the research based on the evaluation criteria for MASH TL-3; (2) proposed guidance for selection and installation of longitudinal barriers on superelevated, curved roadways; (3) proposed designs for modified or new longitudinal barriers for superelevated, curved roadways; and (4) a plan for possible future research to study barrier modifications, changes to roadway geometrics, or both, in response to any identified problems.(6). Present the results of the research at winter and summer meetings of TRB Committee AFB20 and to the AASHTO Technical Committee on Roadside Safety.
STATUS: Proposals have been received in response to the RFP. The panel will work together to select a contractor to perform the work.