In a recent field experiment, a fleet of Global Positioning System—equipped vehicles shared real-time data about network travel times over a wireless network and had their path choices automatically updated accordingly. This paper describes the behavior of these 200 vehicles during the 3-month experiment and illustrates the kind of information that can be derived from the data archive that the vehicles created. Much can be learned about real-time traffic-responsive path choice, travel times, compliance, and more. Planners, designers, and system operators can learn much about the way a system behaves and can sharpen their ability to create systems that work effectively and efficiently under all ranges of use. True path seeking by probe-equipped vehicles will arise when such vehicles become a common part of the vehicle fleet.