of smoothing algorithms, artificial intelligence algo-
rithms, and image processing algorithms are men-
tioned in addition to those identified by Guin. In his
thorough review, (ElSahly and Abdelfatah, 2022) lists
examples from these categories.
Comparative algorithms assess tracked traffic
metrics (such as volume or speed) in relation to prede-
termined thresholds. This group includes the 10 Cali-
fornia Algorithms (Payne and Tignor, 1978), of which
number 7 and 8 are the ones most applied and used
for comparison. Statistical algorithms spot deviations
from the norm in traffic patterns by employing statis-
tical methods. The measured traffic data are treated as
time series and are compared to predicted or histori-
cal data for deviations which might indicate incidents.
These traffic theory-based algorithms include e.g. the
McMaster algorithm (A.I. and Hall, 1989). Another
representative is the All-Purpose Incident Detection
(APID) (Masters et al., 1991). As extension of the
California Algorithm 7 it distinguishes between low,
medium, and high volume traffic and checks for com-
pression waves and incident persistence.
Another summary (Rao and Rao, 2012) includes
developments in measuring urban traffic congestions
globally and establishes two primary variables influ-
encing traffic congestion: micro-level (for example,
the phenomena of too many people wanting to travel
on the same road at the same time) and macro-level
factors (relating to the overall demand of road usage
such as land-use patterns or regional economic dy-
namics). The analysis revealed that there are numer-
ous alternative methods for identifying traffic jams in
urban areas. Rao also provides a summary of the com-
mon congestion measuring measures, such as speed,
trip time, delay, and volume, including counter criti-
cism of each of one of those.
2.2 Incident Forecasting
Kurihara (Kurihara, 2013) proposes an approach
based on ant colony optimisation. It uses a model of
ant behaviour and their use of pheromones for com-
munication. In order to calculate and forecast short-
term traffic congestions at one-minute intervals, in-
tersection computers (also known as “road agents”)
collect measured traffic flows from locally positioned
sensors. The the local traffic flow density is calcu-
lated and pheromones for forecasting the congestion
as well as the density are sent to neighbouring road
agents. A simulation based on a Manhattan-style road
network lead to higher accuracy in congestion fore-
casting than a more usual statistical approach em-
ployed by Balaji et al. (Balaji et al., 2007).
An incident detection technique using dynamic
time warping is proposed by Hiri-o-Tappa et al. (Hiri-
O-Tappa et al., 2007). Here, the likelihood of con-
gestion is determined using speed data from loop de-
tectors. They authors acknowledge that their strategy
falls short in terms of false alarm and time to detect.
Another approach (Huang et al., 2010) offers a
distributed traffic and congestion detection for au-
tonomous cars. Their approach focuses on wirelessly
connected intelligent vehicles that can measure the
speed of the surrounding traffic and the distance be-
tween the leading and trailing vehicles in order to de-
tect shock waves in the velocity. Their assessment
was based on a highway simulation that was put to
the test under various conditions, such as when an ac-
cident or a road merge were present.
To make short-term predictions of abrupt speed
declines, Labeeuw et al. (Labeeuw et al., 2009) com-
pared their methods to those employing Gaussian Pro-
cesses and decision trees. They used common ma-
chine learning techniques (such as the Support Vector
Machine) as reference. In their evaluation, the deci-
sion tree has the maximum correctness.
3 ORGANIC TRAFFIC CONTROL
Urban road networks typically consist of numerous
signalised intersections which are close to one an-
other. The resulting complexity of dynamic road
traffic patterns, the autonomous behaviour of traf-
fic participants, and the resulting uncertainty offer a
good application for approaches which are based on
the concept of “Organic Computing” (M
¨
uller-Schloer
and Tomforde, 2017). In earlier research, the Ob-
server/Controller architecture was used for the Or-
ganic Traffic Management system (OTC) (Prothmann
et al., 2011b), a self-improving traffic signal control
system.
The key features of this decentralised system in-
clude the capacity to adjust traffic light signalisation
in real-time based observed traffic flows, the estab-
lishment of progressive signal systems (also known as
“green waves”) by contacting adjacent intersections
(Tomforde et al., 2008), and the ability to determine
the most efficient routes to points of interest in the
network and pass on this information to drivers (e.g.
via variable message signs) (Prothmann et al., 2011a).
The number of network-wide stops and journey dura-
tions can be reduced, together with fuel consumption
and pollutant emissions.
Figure 1 outlines the multi-layer OTC architecture
which extends an existing intersection controller (IC)
of a node, the “System under Observation and Con-
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