With the advancement in technology and digitalization of society, the number of smartphone users has increased drastically. According to [1], there will be 5.3 billion Internet users by 2023. Due to this, Wi-Fi penetration rate will also increase. For tracking smartphones present inside the vehicles, the uniqueness of Wi-Fi Medium Access Control (MAC) addresses helps a lot. Road traffic monitoring systems can make use of this information for estimating travel time, average speed, and traffic flow in the areas of interest. This article focuses on utilizing Wi-Fi based road-side sniffers to listen to Wi-Fi probe signals broadcasted by the smartphones present inside vehicles for estimating traffic stats of road segments. Hopping Interval (HI) is the rate at which Wi-Fi radio of the sniffer is changed to one of the available channels in ISM band. A channel hopping algorithm is proposed, which adjusts HI of the sniffer according to the current traffic conditions. The proposed algorithm reduces the estimation error and increases the robustness and efficiency of the traffic monitoring system. To validate the algorithm, simulation experiments have been performed in Indian traffic scenarios, and results show that the proposed algorithm is better than static channel assignment on the sniffer with an improvement of 4%. Also, estimated travel time and the ground truth values are found out to be closely related, which assures the suitability of the Wi-Fi based road-side sniffers for traffic monitoring. © 2021 IEEE.