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Page 6 of 14Majalah Ilmiah UNIKOM
Vol.8, No. 2
208
H a l a m a n
Muhammad Aria
Defuzzification
Since the resultant type-reduced output is
an interval type-1 fuzzy set, the output of
fuzzy can be calculate using the average of
its lower and upper bounds
FUZZY LOGIC TRAFFIC SIGNAL CONTROL-
LERS FOR COMPLEX INTERSECTIONS
A fuzzy logic controlled traffic lights uses
sensors that count cars. This provides the
controller with traffic densities in the lanes
and allows a better assessment of changing
traffic patterns. As the traffic distributions
fluctuate, the fuzzy controller can change
the signal light accordingly. The fuzzy logic
controller determines whether to extend or
terminate the current green phase based on
a set of fuzzy rules. The flow diagram of a
controller is shown if Figure 4.
The objective of the Fuzzy traffic light con-
trollers is to reduce the total delay time of
waiting vehicles as well as to avoid heavy
traffic congestion and to synchronize the
local traffic controller with its neighbors,
such as controlling the outgoing vehicles
into neighboring traffic controllers. The fuzzy
traffic lights controller is designed with a
number of useful features so for example is
that if a large volume of vehicles are con-
gested at a neighboring intersection, the
number of vehicles coming into that inter-
section will be reduced.
Fuzzy logic traffic signal controllers con-
tains three modules and this is as shown in
Figure 5. It consist of a Next Phase Module,
a Green Phase Module and a Decision Mod-
ule. The Next Phase Module observes the
condition all the other phases except the
green phase. The Select Max Urgency Phase
selects the most urgent phase. The Green
Phase Module observes the condition of
traffic flow of the green phase only. The De-
cision Module decides the urgency degree
between the Next Phase and the Green
Phase Modules. It also decides by how long
to extend the green phase signal or whether
to change to other phases. For example, if
the Green Phase Module is more urgent
than the Next Phase Module, the green sig-
nal will be extended. On the other hand, if
the Next Phase Module is more urgent than
the Green Phase Module, the Decision Mod-
ule will change the green phase signal to
another phase.
Fuzzy Logic Next Phase Module
NextPhase Module
QueueNum
FrontNumRedTimeQueueNum
(zero, short, medium, large, very large) re-
fers to the number of vehicles remain in a
FrontNum
(short, medium, large, very large) quantifies
the number of vehicles in the link between
the affected intersection and the down-
stream intersections. Information regarding
the quantity of vehicles in the front link, left
link and the right link are all sent to the
fuzzy controller. This input is important in
order to avoid congested links. Another in-
put which is considered in our design is re-
RedTime
very large). It calculates the number of vehi-
cles waiting at a red light. This input is con-
sidered as to avoid the drivers waiting too
long for the green signal. Figure 6 - Figure 8
shows the membership functions of
QueueNum, FrontNum and RedTime.
Ur-
gencyUrgency
traffic condition of the selected phase. If the
Figure 6. Membership functions
for QueueNum