The present invention provides an information processing system that has an incorrectness-risk determination unit, a safety-and-comfort determination unit, and a safety determination unit. The incorrectness-risk determination unit determines whether estimation results for the behavior of a vehicle include an incorrectness risk. The safety-and-comfort determination unit uses a plurality of ranges that are based on travel safety to classify the value of a parameter that indicates the travel state of the vehicle. The safety-and-comfort determination unit also adjusts the travel state of the vehicle and decides on safe behavior for the vehicle such that the value of the parameter is within a range in which travel safety is high. The safety determination unit decides on behavior control for thevehicle. When the safety determination unit acquires, from the incorrectness-risk determination unit, a determination that an incorrectness risk is included, the safety determination unit selects thesafe behavior. When the safety determination unit acquires a determination that an incorrectness risk is not included, the safety determination unit selects the estimation results.