  Vehicle Ad-hoc Networks (VANETs) act as the core of vehicular communications
and provide the fundamental wireless communication architecture to support both
vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication.
Therefore, by leveraging only communication technologies, Connected Vehicles
(CVs) can navigate through the dynamic road network. However, such vehicles are
still in their infancy but are expected to have a significant impact on safety
and mobility such as reducing non-recurrent congestion in case of a vehicle
breakdown or other roadway incidents. To evaluate their impacts, this research
examines the benefits of having CVs when a vehicle breakdown occurs by
developing an intelligent proactive re-routing algorithm. Due to a lack of
real-world data, this paper adopts an integrated simulated framework consisting
of a V2X (OMNET++) communication simulator and a traffic microscopic simulator
(SUMO). The developed algorithm functions such that when a vehicle is broken
down within a live traffic lane, the system detects the breakdown, generates
warning messages immediately and transmits them to approaching vehicles. Based
on the real-time notification, informed vehicles proactively re-route to
alternative roads to avoid the breakdown zone. Two scenarios were developed
where a breakdown occurs within and outside a junction for both V2X-enabled and
disabled systems. Results show that V2X-enabled CV re-routing mechanism can
improve traffic efficiency by reducing congestion and enhance traffic safety by
smoothing accelerations and decelerations of affected vehicles with low
infrastructure costs. The algorithm would be useful to highway agencies
(Department for Transport) and vehicle manufacturers in introducing CVs onto
existing road networks.
