Recent advances in GPS technology, wireless communications technologies, and route guidance systems make it possible to create ATIS systems in which the vehicles both act as probes and engage in real-time route guidance. This paper describes an ATIS experiment in which 200 route guidance-equipped vehicles shared information about network travel times so that they could engage in real-time path choice decision-making. Each vehicle monitored its travel time, shared that information with the other vehicles in the cohort, and then made route guidance decisions based on the integrated information. This paper includes a description of the technology employed, as well as impacts the system had on trust, path choice and routing around congestion, based on reactions of the participants to the system’s features and capabilities. A prognosis for widespread deployment of such technologies is also presented.