In conventional systems, the sensors and detection loops are installed in the top asphalt layer. This means that the sensors are installed in grooves cut or ground into the asphalt after the asphalt is laid. Due to wear and rutting of the asphalt, the sensors must be replaced or adjusted on average every 1.5 years. Moreover, the sensors must be replaced during major maintenance of the road surface. Major maintenance is also necessary more often because installing the sensors affects the structure of the asphalt.
Temperature variations in the summer and winter cause the sensors to separate from the asphalt, requiring the repair of both the sensor and the road surface. This is very expensive.