Parametric effects on the performance of traffic light poles in vehicle crashes

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Collisions between vehicles leaving the road and unforgiving roadside objects (trees, poles, road signs, and other street furniture) are a major road-safety problem. The severity of these collisions depends in part on the incompatibility of vehicle-to-roadside hardware. The literature review shows that a few finite element computer simulation attempts have been conducted using existing traffic roadside hardware, without further research to enhance their safety performance against vehicle impacts. The aim of this research is to contribute to the efficient design of traffic light poles involved in vehicle frontal collisions by developing an experimentally calibrated, computer-based, finite element model capable of capturing all impact characteristics. This is achieved by using the available nonlinear dynamic analysis software ȁLS-DYNAȁ, which can accurately predict the dynamic response of both the vehicle and the traffic light pole. A parametric study was conducted to evaluate the effects of key parameters on the response of the pole embedded in soil when impacted by vehicles. These parameters included soil type (clay and sand), pole material type (steel and aluminum), embedment length of the pole, and vehicle impacting speed. It is demonstrated from the results of the numerical analysis that the aluminum pole–soil system has favorable advantages over steel poles, where the aluminum pole absorbed vehicle impact energy in a smoother manner, which leads to smoother acceleration pulse and less deformation of the vehicle than those encountered with steel poles. Also, it was observed that clayey soil brings slightly more resistance than sandy soil, which helps in reducing pole movement at ground level. Moreover, results show that the longer the embedment length, the better the intrusion and acceleration of the vehicle.