Abstract
The degradation of road network performance due to incidents is a major
concern to traffic operators. The development of urban traffic incident
management systems requires a comprehensive understanding of traffic
dynamics during incidents. Recently, the concept of the macroscopic
fundamental diagram (MFD) contributed to such an understanding and has
been used in a wide range of applications. However, the MFD is merely
reproducible under recurring traffic patterns. Motivated by a few
studies which argue the existence of the MFD with a clockwise hysteresis
loop during incidents, we tackle this limitation of the MFD and propose
a framework to study the characteristics of the MFD under non-recurring
congestion. More specifically, we introduce a criticality score (CS)
which represents network redundancy and postulate that links with a
higher level of CS impose a larger hysteresis loop on the MFD. We design
an experiment in a microscopic traffic simulation to study the relation
of closed links and the resulting MFDs. The results confirm our
postulation and we observe that links with similar CS have a comparable
impact on the shape of the MFD. The main contribution of this paper is
the possibility to develop a framework for incident detection in urban
networks under limited sensor coverage. However, the findings of the
study may strongly rely on the assumptions, for instance, the network
structure, the OD pairs, and drivers route choice during incidents.
Thus, future studies are required to study other network topologies as
well as more realistic driver route choice during incidents.