An on-board system comprising: a plurality of detectors provided to a vehicle; a controller configured to control an on-board instrument mounted on the vehicle based on detection information indicating a result of detection by the detectors; and a first network connecting the on-board instrument and the controller in an intercommunicatable manner; characterized in that: the controller is configured to control the on-board instrument mounted on the vehicle based on detection information indicating a result of detection by each of the detectors; and by a detector hub interposed between each of the detectors and the controller in an intercommunicatable manner and configured to collect the detection information obtained by the detectors and transmit the collected detection information to the controller; a second network independent from the first network and connecting the detectors, the detector hub, and the controller in an intercommunicatable manner, wherein the first network connects the on-board instrument and the controller through a protocol conversion unit configured to perform protocol conversion in an intercommunicatable manner by a plurality of protocols different from each other, and the second network connects the detectors, the detector hub, and the controller in an intercommunicatable manner by a single protocol without the protocol conversion unit. a plurality of detectors provided to a vehicle; a controller configured to control an on-board instrument mounted on the vehicle based on detection information indicating a result of detection by the detectors; and a first network connecting the on-board instrument and the controller in an intercommunicatable manner; characterized in that: the controller is configured to control the on-board instrument mounted on the vehicle based on detection information indicating a result of detection by each of the detectors; and by a detector hub interposed between each of the detectors and the controller in an intercommunicatable manner and configured to collect the detection information obtained by the detectors and transmit the collected detection information to the controller; a second network independent from the first network and connecting the detectors, the detector hub, and the controller in an intercommunicatable manner, wherein the first network connects the on-board instrument and the controller through a protocol conversion unit configured to perform protocol conversion in an intercommunicatable manner by a plurality of protocols different from each other, and the second network connects the detectors, the detector hub, and the controller in an intercommunicatable manner by a single protocol without the protocol conversion unit. the controller is configured to control the on-board instrument mounted on the vehicle based on detection information indicating a result of detection by each of the detectors; and by a detector hub interposed between each of the detectors and the controller in an intercommunicatable manner and configured to collect the detection information obtained by the detectors and transmit the collected detection information to the controller; a second network independent from the first network and connecting the detectors, the detector hub, and the controller in an intercommunicatable manner, wherein the first network connects the on-board instrument and the controller through a protocol conversion unit configured to perform protocol conversion in an intercommunicatable manner by a plurality of protocols different from each other, and the second network connects the detectors, the detector hub, and the controller in an intercommunicatable manner by a single protocol without the protocol conversion unit.