Placement of traffic barriers on roadside and median slopes – guidelines based on numerical simulations

Abstract

This paper presents the results of numerical studies performed to evaluate the performance of four commonly used traffic barriers on roadside and median slopes. The selected guardrail/barrier systems are the modified G4(1S) W-beam guardrail, modified thrie-beam guardrail, Midwest guardrail system and modified weak-post W-beam guardrail. For barriers placed on slopes, vehicle impact height varies depending on the trajectory of the vehicle along the ditch section and lateral offset of the barrier. Multi-rigid-body dynamic analysis code, CARSIM, is used to identify trajectories of the vehicles traversing various roadside and median cross-slopes. Performance limits of each barrier in terms of acceptable vehicle impact heights are superimposed on the trajectory data to identify safe lateral offset locations for each barrier. The resulting placement guidelines are then refined using the responses obtained from LS-DYNA simulations that capture the full encroachment event from departure of the vehicle off the travelled way through impact with the barrier.