Abstract: A roadside relay apparatus includes first, second, and third communication units to which first, second, and third lines described below are connected, a communication processing unit configured to relay or intercept communication between the first and second communication units, and an information processing unit configured to generate signal information for a vehicle, based on a control command, for controlling a traffic signal controller, received by the first communication unit and based on details of control, performed by the traffic signal controller, received by the second communication unit, and to output the generated signal information to the third communication unit. The first, second, and third lines are communication lines for wired communication with a central apparatus of a traffic control system, the traffic signal controller, and a communication apparatus that belongs to a communication system configured to wirelessly provide information to the vehicle, respectively.