A traffic information communication system in which an on-board communication device (300; 3000) equipped in a vehicle and a mobile terminal carried by a pedestrian perform radio communication, wherein the on-board communication device (300; 3000) includes: a navigation unit (100; 1000) that is adapted to obtain at least location information of its own vehicle equipped with the on-board communication device (300; 3000) and vehicle drive information including a vehicle ID specifying the own vehicle; and a communication device unit that is adapted to broadcast the vehicle drive information obtained by the navigation unit (100; 1000) at a predetermined frequency and to output vehicle drive information received from an on-board communication device of another vehicle or pedestrian information received from the mobile terminal to the navigation unit (100; 1000), characterised in that the navigation unit (100; 1000) is adapted to add a vehicle ID specifying said other vehicle as a to-be-watched vehicle or a terminal ID specifying said mobile terminal as a to-be-watched terminal to the vehicle drive information of its own vehicle and to transmit the vehicle drive information to the communication device unit, in the case of detecting the other vehicle or the mobile terminal approaching in a drive direction of its own vehicle from the vehicle drive information received by the communication device unit of the on-board communication device (300; 3000), and the on-board communication device (300; 3000) of the other vehicle or the mobile terminal that receives the vehicle drive information is adapted to increase a transmission frequency or transmission power of the own vehicle drive information or pedestrian information, in a case where the to-be-watched vehicle ID or to-be-watched terminal ID included in the received vehicle drive information is identical to its own vehicle ID or terminal ID, and to reduce said transmission frequency, in a case where the received to-be-watched vehicle ID or to-be-watched terminal ID is not identical to its vehicle ID or terminal ID. a navigation unit (100; 1000) that is adapted to obtain at least location information of its own vehicle equipped with the on-board communication device (300; 3000) and vehicle drive information including a vehicle ID specifying the own vehicle; and a communication device unit that is adapted to broadcast the vehicle drive information obtained by the navigation unit (100; 1000) at a predetermined frequency and to output vehicle drive information received from an on-board communication device of another vehicle or pedestrian information received from the mobile terminal to the navigation unit (100; 1000), characterised in that the navigation unit (100; 1000) is adapted to add a vehicle ID specifying said other vehicle as a to-be-watched vehicle or a terminal ID specifying said mobile terminal as a to-be-watched terminal to the vehicle drive information of its own vehicle and to transmit the vehicle drive information to the communication device unit, in the case of detecting the other vehicle or the mobile terminal approaching in a drive direction of its own vehicle from the vehicle drive information received by the communication device unit of the on-board communication device (300; 3000), and the on-board communication device (300; 3000) of the other vehicle or the mobile terminal that receives the vehicle drive information is adapted to increase a transmission frequency or transmission power of the own vehicle drive information or pedestrian information, in a case where the to-be-watched vehicle ID or to-be-watched terminal ID included in the received vehicle drive information is identical to its own vehicle ID or terminal ID, and to reduce said transmission frequency, in a case where the received to-be-watched vehicle ID or to-be-watched terminal ID is not identical to its vehicle ID or terminal ID.