This article examines the economics of traveler information from probe vehicles to understand how many probes are needed to provide useful information and how that probe information might be suppliedto travelers. Probes differ from permanently installed roadway detection devices both because they provide information that is less current andbecause an information system centeredon this technology can be organizedin the form of private clubs rather than a government agency. This article estimates travel time associatedwith various shares of probes among the fleet by simulating different levels of probes, information subscription, and congestion. It examines the travel time saving under both recurring and nonrecurring congestion. With the latter, a low frequency of probes is sufficient to detect the incident andenable information consumers to choose alternates. However, smoothing the stochastic nature of traffic under recurring congestion requires a relatively high share of probes, depending on the level of congestion.