  In the last few years, the Vehicular Ad-hoc Network (VANET) has come to be an
important area of research. Significant research has been conducted to improve
the performance of VANETS. One output of further research conducted on VANET is
the Vehicular Delay Tolerant Network (VDTN). It is an application of the mobile
DTN where nodes relay messages in the network using a store-carry-forward
approach. Due to its high mobility, it suffers frequent disconnections and also
congestions at nodes which leads to message drops. To minimize the rate of
message drops and so optimize the probability of message delivery so that
drivers are increasingly aware of the situation of the road, we propose a
congestion control mechanism: Congestion Aware Spray and Wait (CASaW) protocol
in this work so as to optimize the rate of message delivery to its destination
and so increase the awareness of drivers in the vehicular environment thereby
improve road safety. The results have shown that our proposition performed
better than other classical VDTN protocols in terms of message delivery
probability and rate of packet drops performance measures. We used the
Opportunistic Networking Environment (ONE) simulator to implement the classical
VDTN protocols: the PROPHET protocol, the Epidemic protocol, the MaxProp
protocol and the Spray and Wait Protocol. The simulation scenarios shows a
better performance for the congestion control mechanism we propose as it
maintains a good message delivery rate as well as minimize the rate of packet
losses thereby optimizing the chances of messages getting to their destinations
and so improve road safety.
