Road Vibrations as a Source to Detect the Presence and Speed of Vehicles

The study of vehicular traffic is essential for modern cities to determine the efficiency of their current roads and to plan new infrastructure that keeps the mobility of its inhabitants. Technologies that provide detailed data of the current situation on the roads are needed to reduce journey times and pollution emissions and consequently improve the quality of life of the people. Smart streets featuring sensor networks offer the possibility to study with high accuracy the traffic conditions on every point of the road. Using sensor networks parameters like speed, travel direction, and type of vehicles can be precisely calculated. Furthermore, it is possible to determine in real time the peak hours and the site of accidents. Different sources such as sound, magnetism, or vibrations can be used to monitor the traffic flow. From them, road vibrations are of special interest because of their potential for energy harvesting by using piezoelectric films and thus reducing the dependence on external power sources. This paper presents a study that provides the bases to develop a 2-D sensor network using MEMS accelerometers placed on the width and length of the road surface to monitor continuously the traffic flow. In this paper, piezoelectric acceleration sensors, based on the same measuring principle as MEMS accelerometers, are used with the objective to analyze in detail the amplitudes and frequency ranges in which vibrations occur. From this information, the algorithms to determine the presence of vehicles, their travel direction, and speed are developed.