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Major Building blocks of the Area Traffic Control Systems are: Vehicle
Detectors, Intersection Controller, Communication Network, Application Software
and Central (Regional) Control System which are described below:
Vehicle Detectors is used to detect the presence of vehicles, to collect data
to find average speed, vehicle flow, vehicle density, queue length measurement.
VD acts as a nodal point between vehicle and intersection controller.
Detector could be of various types example-ultrasonic, microwave radar,
infrared laser radar, non-imaging passive infrared, video imaging, acoustic
array, magnetic loop Inductive loop vehicle detector is commonly used.
Fig. 1 is showing example of Vehicle Detectors.
Figure 1:
Example of Vehicle Detectors (Source Muralidharan, 2006)
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In Fig. 1 two detectors are shown, 1 is for straight
going traffic which will detect the vehicle which will go straight and 2 is
right turning traffic which will detect the vehicle which will take right turn
from there.
It is the micro-macro computer.
It placed at intersection for temporary storage of data.
It collects the data from vehicle detector and sends it to the central control.
Central control processed the data and sends it back to the intersection
controller which then implements the signal timings as instructed at the
intersection.
Intersection controller for each set of traffic signals receives the signal
states from the control system.
The communication network transfers data from the signal controller, to the
central control station where optimized signal timings and phases are
determined and it again transfers information to the signal controller as per
the data processed.
It transfers the data obtained from detectors to central control which then
implements the signal timings as instructed at the intersection.
Fig. 2 is showing the communication network.
Figure 2:
Communication Network (Source: Muralidharan, 2006)
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Application software is the software used behind the whole ATC system which
performs the entire task.
It is a large and complex program involving multiple systems, various
procedures for implementation.
Functions of Application software are: It defines the architecture flows,
activities and functions and user services that planners want to deliver.
It is the main unit of ATC.
In this unit collected traffic data is processed to optimize various traffic
parameters like-signal timing, phase change, delay Important and major task of
ATC system is performed by this unit.
It supervises all the units of ATC.
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