A vehicle system includes a warning device and at least one electronic control unit. The at least one electronic control unit is configured to present a light stimulus to a driver, and determine whether the driver is facing forward, determine whether the driver holds a steering wheel, and cause the warning device to perform a first warning when it is determined that the driver is not facing forward while the light stimulus is being presented. The first warning is either the vibration or the sound. The at least one electronic control unit is configured to perform a second warning when it is determined that the driver does not hold the steering wheel before a predetermined time elapses after the first warning is started. The second warning includes the vibration and the sound.