B. Approach
The application of inter-vehicular communication over a MANET raises several interesting issues in regard to data
forwarding. One such issue is that an unpredictable traffic has both a limited area of relevance and a limited time of relevance. For example, carriers should not forward information about road closures after the road has re-opened. This requires carriers to not only forward received messages, but also analyze the semantics of the messages to first determine if they should be forwarded. As another example, carriers may be traveling to destinations hundreds of miles away from the traffic slowdown. It would be wasteful for these carriers to broadcast the notification of the traffic slowdown to all vehicles it encounters.VETRAC proposes to introduce relevance filtering at the carriers before forwarding event messages. Upon receiving an event message, the carrier will look at the location of the event and the expiration time of the event (e.g., lane re-opening time). If the carrier has exceeded a threshold distance away from the location or the expiration time of the event has passed, the carrier will discard the message. Otherwise, the carrier will add the message to its outgoing message queue.