  IEEE 802.11p is one of the key technologies that enable Dedicated Short-Range
Communications (DSRC) in intelligent transportation system (ITS) for safety on
the road. The main challenge in vehicular communication is the large amount of
data to be processed. As vehicle density and velocity increases, the data to be
transmitted also increases. We proposed a protocol that reduces the number of
messages transmitted at a vehicle according to the level of danger that the
vehicle experiences. The proposed protocol measures inter-vehicle distance, as
the representative of the danger of a vehicle, to determine the priority for
transmission. Our results show that this prioritization of transmissions
directly reduces the number of transmitters at a time, and hence results in
higher performance in terms of key metrics--i.e., PDR, throughput, delay,
probabilities of channel busy and collision.
