Abstract: This paper proposes a repeatedly-woken based scanning algorithm (RBSA), which is tailored and optimized for the road network surveillance within low duty-cycle WSNs. Our design is mainly based on the facts that the movement of targets (e.g., vehicles) is always confined in roadways with limited speed and the road network maps are normally easy to obtain from the map services provider or from the Internet. The main idea is that each sensor node along the roadway successively wakes up and sleeps for k times in one round or sleeps with sufficient use of the overlapped sense area between two adjacent nodes, while the detection of moving targets is guaranteed before they reach specific protection points such as temporary base camps. The duty cycle of each node is consequently minimized, resulting in obvious extension of the network lifetime. We provide complete theoretical analysis on the performance of RBSA in terms of network lifetime and average detection delay. Extensive simulation shows that RBSA extends network lifetime by 80% in typical configuration parameters compared with the original classic scanning algorithm, while only small average detection delay is extended.