  Many parties claim the technical significance of Dedicated Short-Range
Communications (DSRC) in intelligent transportation system (ITS) for promotion
of transportation safety. The main challenge in this key vehicle-to-everything
(V2X) standard is high odds of network congestion. Furthermore, in accordance
with a V2X network being inherently dynamic in key parameters such as vehicle
density and velocity, the networking behavior of a DSRC system is usually
highly complicated to analyze. In addition, the United States Federal
Communications Commission (US FCC) recently announced the "5.9 GHz band
reform," which reduced the dedicated bandwidth for DSRC to 10 MHz from 75 MHz.
Motivated from these, the necessity of "lightening" the networking load of a
DSRC network has become essential to keep safety-related operations without
performance deterioration. To this end, this paper proposes a protocol that
prioritizes transmission of a basic safety message (BSM) at a vehicle according
to the level of danger that the vehicle experiences. The proposed protocol uses
the distance between a danger source and a vehicle as the metric to determine
the priority for transmission. Our results show that this protocol prioritizes
the transmission opportunity to dangerous vehicles, and hence results in higher
performance in terms of key metrics--i.e., average delay, throughput, and
inter-reception time ($\mathsf{IRT}$).
