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event-based architectures as the basis for trac management systems. Those ar-
chitectures collect data from multiple sources along the road, building up events
of higher level of abstraction in order to decide which possible actions can be
applied into a tra c problem.
In this paper a combination of CEP and ESP is proposed for the problem of
processing and classifying events generated by diverse sources, detecting complex
patterns and creating automatic outputs that raise the situation awareness. This
awareness makes it feasible for a trac control center to warn drivers by means
of panels or directly through vehicular communications links based on cellular
networks or wireless local area networks.
The system under consideration focuses on trac congestion detection and
launches different actions depending on the severity of the congestion. In ad-
dition to the informative messages, vehicles may receive some other services
when subscribed. These messages can be formatted in text, graphic or voice
mode. Geospatial services are web-based and compliant with the Open Geospa-
tial Consortium (OGC) standards [4].
The rest of the paper goes as follows: Section 2 describes the sensors in the
vehicle, its data fusion model and the set of kinematic vehicles models that
represents the motion behavior of the vehicle. Sections 3 and 4 introduce the
architectures for event modelling and processing. Section 5 presents services
associated to trac congestion. The implementation of the system in depicted
in Section 6, and Section 7 concludes the paper.
2
Road Congestions
First step in order to detect congestion is to define what is a congestion. In
the system under consideration it is assumed that there is a congestion when
vehicles must drive at a speed lower than the minimum speed limit. In Spain
this value is 60 km/h in highways. With this number, and the relation between
feasible average speed and tra c density shown in Fig. 1, several congestion
levels are proposed. The system will detect the tra c densities associated to
these situations. For the case of roads with speed limit 120 km/h (solid line in
Fig. 1), congestion levels are presented in Table 1.
Table 1. Congestion Levels
Density (vehicule/km/lane) Congestion Level
20 — 30
Slow Tra c
30 — 40
Slight Congestion
40 — 50
Middle Congestion
50 — 60
High Congestion
>
60
Serious Congestion
 
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