Wireless technologies can help solve traffic congestions in urban environments, where road infrastructures develop slower than the sometimes exponential growth in the number of cars in traffic. We present a system for traffic control and congestion avoidance. The system monitors traffic using cars acting as data collectors. It aggregates the monitoring data into a traffic model, further used by cars to dynamically adjust their routes. We propose novel metrics for traffic, and present evaluation results that show the capabilities of the proposed congestion avoidance model to correct traffic conditions.