Analysis of the Influence of the Front Vehicle on the Propagation Loss of ETC System of the Back Vehicle

As a typical application of intelligent transportation systems (ITS), the electronic toll collection (ETC) system has been widely used on highways due to its excellent toll efficiency. In the actual traffic environment, there usually exists more than one vehicle in the radiation area of the road-side units (RSU) at the same time, and the front vehicle will affect the ray paths between the RSU and the on-board units (OBU) of the back vehicle. Here we studied the front vehicle’s impact on the ETC system’s path propagation loss by ray tracing technology and Uniform Theory of Diffraction (UTD). Firstly, we simplified the vehicle body structure into two equivalent geometric models. Four situations were considered according to the vehicles’ front and rear positions. We analyzed each scenario’s propagation loss models under line-of-sight (LOS) and non-line-of-sight (NLOS) conditions based on the distance change among RSU, OBU, and the front vehicle. Finally, we developed an ETC comprehensive test equipment to measure the propagation loss of the four scenarios at a toll station. Both simulation and experiment results indicate that the propagation loss models proposed in this paper are valid.