Page 27 - TT Magazine Feb-Mar 2019

TRAFFIC MANAGEMENT

A varying traffic conditions. To have a operations. Over a period of time,
drive through the snarly
Fixed time systems do not adjust to
several detection methods such as
traffic in a metro city
in India will make you
inductor loops, infrared and video have
junction responding to varying traffic
question, why am I not
demand, vehicle actuated systems
been used. Video detection is most
getting enough green
time or why am I not getting a green could be used, but in India these are suitable for Indian conditions, primarily
limited to a particular junction, in other
because it is non-intrusive and captures
through-out the stretch or why am words an isolated system. A growing images for verification.
I waiting longer than needed at a Indian city requires traffic managed at SCATS, through the controllers
junction? As a pedestrian, you might an area level where in one signal works and software, manages three main
wonder if there is a button you can in tandem with others – a coordinated parameters to achieve efficient traffic
press to help you to cross the road. signal system. flow and signal coordination.
Authorities in India have long been There are different types of ATCS • Cycle Time: The total time of all
exploring solutions that adapt to technologies across the globe – new phases running in sequences in a
changing traffic conditions in cities and old, mathematical and algorithmic, cycle.
by the hour and the day. Adaptive upstream detection and stop-line • Phase Split: The proportion of cycle
Traffic Control System (ATCS) is not detection. time allocated to each phase in a
entirely new to India, however, the Sydney Coordinated Adaptive Traffic junction.
National Smart Cities Mission has Systems or commonly known as
helped in bringing in a broader level SCATS was developed in 1970’s by a • Offset: The time relationship
of understanding and implementation government entity in Australia known between two green phases of
successive set of signals in a
experience. as Roads and Maritime Services (RMS). coordinated system.
The graph chart below is a plot of the Since then SCATS has been deployed in Degree of Saturation (DS) is a traffic
traffic junction cycle time (total time of more than 29 countries, 270+ cities and demand measurement parameter
all sequences in a cycle) through-out the across 40000+ junctions. used by SCATS. DS represents how
duration of a typical day. The spikes and SCATS is an area traffic management effectively the road is being used. DS
dips are signal times adjusting to the system consisting of hardware, greater than unity (insufficient green
flow of traffic where as the one which software and a unique traffic control time to satisfy demand) will occur in
is relatively flat belongs to fixed time that operates in real-time, adjusting congested conditions, and SCATS is
systems that are prevalent in our cities signal timings in response to variations known to quickly respond to such an
today. The area between the plots is the in traffic demand and system capacity over saturated condition.
time saved for commuters, this time- as they occur. The hardware consists
saving when extrapolated for a year for of a controller and a detection system When congestion occurs, the system
a busy city, will be significant – certainly installed at each junction. estimates the full extent of unmet
demand using a parameter known as
improving travel time – a key factor for Detection of real-time traffic reconstituted volume. Reconstituted
city’s Citizen Happiness Index. conditions is a critical input for efficient
volume is estimated using the calibrated
and measured conditions at each detector.
It records the duration of congestion for
traffic performance purposes and can be
configured to respond adaptively to a
measured congested state.
The success of SCATS in Asia is an
indication of it being adaptable to
heterogeneous traffic conditions – that
is different types of vehicles moving in a
non-lane pattern. Two possible reasons
for this could be:
Stop-line detection method adopted
in which traffic volumes are measured
at the stop-line of the signal.
Negative feedback principle – A
method where the output of a process

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