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Now-a-days, controlling traffic congestion relies on having an efficient and
well-managed traffic signal control policy.
Traffic signals operate in either pre-timed or actuated mode or some
combination of the two.
Pre-timed control consists of a series of intervals that are fixed in duration.
They repeat a preset constant cycle.
In contrast to pre-timed signals, actuated signals have the capability to
respond to the presence of vehicles or pedestrians at the intersection.
Actuated control consists of intervals that are called and extended in response
to vehicle detectors.
The controllers are capable of not only varying the cycle length & green times
in response to detector actuation, but of altering the order and sequence of
phases.
Adaptive or area traffic control systems (ATCS) belong to the latest generation
of signalized intersection control.
ATCS continuously detect vehicular traffic volume, compute optimal
signal timings based on this detected volume and simultaneously implement them.
Reacting to these volume variations generally results in reduced delays,
shorter queues and decreased travel times.
Coordinating traffic signals along a single route so that vehicles get
progressive green signal at each junction is another important aspect of ATCS.
In the subsequent pages, the operating principles and features of
Vehicle-Actuated Signals & Area Traffic Control Systems will be briefly
discussed.
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