Vehicular traffic monitoring and control has had a strong infrastructure bias—data is collected centrally, processed, and then redistributed to travelers and other clients. There are several efforts to decentralize traffic monitoring by leveraging advanced local area wireless technology. This paper describes our implementation of such a travelercentric system, called Autonet. Each Autonet client exchanges network knowledge wirelessly with other, nearby clients. It is demonstrated that knowledge about traffic state can be propagated using this system. The client programs were also used to test the actual throughput possible for messages sent from one vehicle to another using 802.11b wireless hardware. These measurements establish the maximum throughput at about 4,000 incidents for two vehicles moving in opposite directions at highway speeds.