SummaryIn the traffic monitoring system, the transportation department generates the traffic map to report the real‐time traffic conditions, so as to provide more efficient service for drivers. However, if the vehicle obtains the local traffic conditions that the driver is more concerned about from the remote server, it will consume a heavy bandwidth and incurs an increased response delay. Generating and broadcasting local traffic conditions through fog computation is a feasible method to reduce communication costs, and most existing traffic monitoring systems based on fog computation are implemented using Bilinear Pairing operations. In this paper, we propose Lightweight and Privacy‐preserving Traffic Monitoring (LPTM) scheme with Elliptic Curve Cryptosystem, an optimized Timed Efficient Stream Loss‐tolerant Authentication protocol is adopted to achieve efficient and secure communication, and we also use an identity‐based signature scheme with partial message recovery to effectively shorten the length of the fog node broadcast message. Detailed security proofs show that the requirements of security and privacy are all achieved, and better simulation performance is presented in both computation and communication overhead.