A self-luminous road sign system comprises a plurality of sensor units 1 . . . 1 each of which is equipped at least with a visibility meter and an illuminance meter, or which may be equipped with an anemovane and a thermometer as well as the visibility meter and the illuminance meter; and an information processing and management department 2 for centralized management of weather information detected by the plural sensor units in order to predict any danger in the road observation area, wherein the output information from the information processing and management department 2 is displayed on road installations 4 . . . 4 connected via a network. Based on the road background brightness obtained by the illuminance meter in the sensor unit, the optimum luminous brightness which provides a predetermined contrast is calculated. Based on this optimum luminous brightness and depending on the visibility information outputted from the visibility meter, the luminous brightness or information display of the sign part is controlled.