An apparatus assesses an arousal level of a driver of a vehicle. The apparatus includes a processor and a memory storing a computer program, which when executed by the processor, causes the processor to perform operations. The operations include acquiring personal data of the driver, which are detected by one or more sensors when the vehicle is traveling. The operations also include developing, by machine learning with the acquired personal data, a model for estimating an arousal level to personalize the model to the driver, and determining the arousal level of the driver based on the personalized model.
