An on-board unit of a vehicle includes first and second transceivers. A processor of the vehicle monitors transmissions received from the first and second transceivers, receives an incoming message sent to the processor from the first transceiver, the incoming message being designated for distribution to roadway participants, identifies based on the monitored transmissions whether the second transceiver is in communication with devices of roadway participants available to receive outgoing messages, and if so, construct an outgoing message based on the incoming message and send the outgoing message via the second transceiver, and monitors vehicle network bus traffic to identify a current speed of the vehicle, and responsive to the vehicle moving at least a threshold speed, construct and send vehicle-information outgoing messages including roadway observations of the vehicle, using the first transceiver and the second transceiver, the vehicle-information outgoing messages being designated for distribution to the roadway participants.