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 completes 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 includes (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.