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Vehicle Dynamics Modeling and Simulation Approach for Safety Performance Evaluation of Cable Barriers in Curves Open Access

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Cable barriers are an alternative safety countermeasure to rigid or semi-rigid barriers (Guardrails, Concrete Barriers, etc.) for run-off-road crashes on highways with moderate to light traffic flow. Due to their low installation cost and reduced impact severity, the State DOTs have installed them in locations such as highway medians, where the number of crashes is relatively small but often fatal. In 2009, over five thousands crashes resulted from crossovers, accounting for 17% of the US fatal crashes. These crashes are especially severe because they often lead to head-on collisions at higher highway speeds (55mph [88.5km/h] and above), hence causing even higher delta-V (total change in vehicle velocity over the duration of the crash event, it is the most widely used severity metric in crash databases).In order to optimize the use of these highway median cable barriers, a better understanding of the vehicle behavior as it crosses the median is required. This thesis focuses on the development of tools and methods to produce guidelines for the design selection and appropriate placement of these barriers, to enhance safety. An automated process is implemented for vehicle dynamics modeling and simulation of trajectories across several different median geometries and conditions.The commercial software CarSim® is used for vehicle dynamics modeling of a small sedan passenger car (Honda Civic) and a pickup truck (Chevrolet C2500), representative from the highway traffic fleet. Extensive analyses were conducted to simulate the trajectories of these vehicles using a large range of speeds, yaw angles, and median geometries. The medians studied were symmetric v-shape ranging from 16ft-wide to 56ft-wide, with slopes from 12:1 to 4:1. They have been analyzed with five different horizontal curves of radii 300m [984ft], 600m [1,969ft], 900m [2,953ft], 1,200m [3,937ft], and 3,505m [11,500ft]. Over 8,000 simulation cases have been executed. In each case, two critical points on the vehicle are traced to check the interaction with the barriers. The results evaluate the potential for under/over-ride of any cable barrier depending on its placement within a specific median and demonstrate the safe placements of the barriers. The developed tools can be used for other barriers and types of medians.

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