A collision avoidance system, comprising: an onboard acquisition unit provided in a vehicle traveling on a road and configured to acquire state quantity data indicating a state quantity of a pneumatic tire of the vehicle; an onboard transmission unit provided in the vehicle and configured to transmit the state quantity data acquired by the onboard acquisition unit to a data acquisition roadside device installed on the road; an abnormality determination unit configured to determine whether or not the state quantity data is abnormal; and a management device including: a data acquisition unit configured to acquire the state quantity data from the data acquisition roadside device; a data storage unit configured to store the state quantity data acquired by the data acquisition unit; and a data distribution unit configured to distribute the state quantity data determined as abnormal by the abnormality determination unit, characterized in that the state quantity includes an amount of wear of the pneumatic tire, the collision avoidance system comprising: a following vehicle acquisition unit comprising a camera provided in the following vehicle traveling behind the vehicle and configured to acquire amount of wear data indicating the amount of wear of the pneumatic tire of the vehicle; and a following vehicle transmission unit provided in the following vehicle and configured to transmit the amount of wear data acquired by the following vehicle acquisition unit to the data acquisition roadside device; wherein the abnormality determination unit is configured to determine whether or not the amount of wear data is abnormal, and the data distribution unit is configured to distribute the amount of wear data determined as abnormal by the abnormality determination unit to at least one of the vehicle and a second following vehicle traveling behind the following vehicle. an onboard acquisition unit provided in a vehicle traveling on a road and configured to acquire state quantity data indicating a state quantity of a pneumatic tire of the vehicle; an onboard transmission unit provided in the vehicle and configured to transmit the state quantity data acquired by the onboard acquisition unit to a data acquisition roadside device installed on the road; an abnormality determination unit configured to determine whether or not the state quantity data is abnormal; and a management device including: a data acquisition unit configured to acquire the state quantity data from the data acquisition roadside device; a data storage unit configured to store the state quantity data acquired by the data acquisition unit; and a data distribution unit configured to distribute the state quantity data determined as abnormal by the abnormality determination unit, a data acquisition unit configured to acquire the state quantity data from the data acquisition roadside device; a data storage unit configured to store the state quantity data acquired by the data acquisition unit; and a data distribution unit configured to distribute the state quantity data determined as abnormal by the abnormality determination unit, characterized in that the state quantity includes an amount of wear of the pneumatic tire, the collision avoidance system comprising: a following vehicle acquisition unit comprising a camera provided in the following vehicle traveling behind the vehicle and configured to acquire amount of wear data indicating the amount of wear of the pneumatic tire of the vehicle; and a following vehicle transmission unit provided in the following vehicle and configured to transmit the amount of wear data acquired by the following vehicle acquisition unit to the data acquisition roadside device; a following vehicle acquisition unit comprising a camera provided in the following vehicle traveling behind the vehicle and configured to acquire amount of wear data indicating the amount of wear of the pneumatic tire of the vehicle; and a following vehicle transmission unit provided in the following vehicle and configured to transmit the amount of wear data acquired by the following vehicle acquisition unit to the data acquisition roadside device; wherein the abnormality determination unit is configured to determine whether or not the amount of wear data is abnormal, and the data distribution unit is configured to distribute the amount of wear data determined as abnormal by the abnormality determination unit to at least one of the vehicle and a second following vehicle traveling behind the following vehicle.