The advancement of information technology has facilitated the development of various types of roadside vehicle detection sensors. The monitoring of these sensors constitutes a critical component of sensing systems and serves as a foundation for the reliability of diverse traffic data. Current sensing systems exhibit a significant limitation in their monitoring capabilities, as they predominantly focus on whether the sensors are operational, neglecting a more comprehensive assessment of their performance. To address this gap, this paper introduces two primary indicators: operational reliability and performance reliability, alongside five secondary indicators: online status quality, data status quality, communication status quality, regional detection location accuracy, and target detection accuracy. Through extensive monitoring of three roadside millimeter wave radars, the findings indicate that the proposed sensing system effectively fulfills the multidimensional management requirements of traffic management authorities concerning sensor performance.