Wireless mesh networks (WMNs) are currently used to provide broadband access to the Internet anytime and anywhere. Generally, WMNs consist of mesh routers equipped with one or more interfaces allowing connectivity to the Internet through gateways. To route traffic from sources to destinations, many routing protocols have been proposed in the literature. However, most of them take into account at most one metric (e.g., interferences, packet losses, and load at gateways). Moreover, almost all of these schemes consider only one type of interferences: interflow or intraflow. In this paper, we propose a new source routing and gateway selection scheme, which is called source-based routing (SBR), that improves the performance of WMNs. SBR uses a novel routing metric, which is a combination of packet losses, intraflow and interflow interferences, and load at gateways, to select best paths to reach selected gateways. Simulation results show that the proposed SBR improves the network performance and outperforms existing routing schemes, which are based on expected transmission count (ETX), nearest gateway (NG; i.e., shortest path to gateway), load at gateways (LG), or interference ratio (IR); more specifically, SBR yields 33%, 26%, 13%, and 10% more throughput compared with LG, ETX, NG, and IR, respectively.