A system includes one or more transponders, a number of sensors, a tracking sub-system, and a billing sub-system. Each transponder is located in a vehicle capable of being driven on a road having at least a first lane and a second lane in which vehicles move in a same direction. Each sensor is movably located at a point along the road to detect the transponder of each vehicle that has changed between the first and the second lanes at the point. The tracking system is communicatively coupled to the sensors to track when and at which of the points the vehicles have changed between the first and the second lanes. The billing system is to periodically bill users of the vehicles based on when and where the vehicles are driven in the second lane of the road.