5
S
ECTION
2
Actuation –
Traf
fi
c actuation allows traf
fi
c
fl
ow to
control green times within speci
fi
ed timing param-
eters. A microwave traf
fi
c sensor, video detection
or other actuation device, is attached to the ma-
chine which detects approaching traf
fi
c. When a
vehicle is detected, the sensor sends a command
to the controller putting that phase in queue (refer
to Sensor Locking for further options). Only one
signal in a phase needs to detect a vehicle in order
for that phase to be placed in queue.
Phase –
a movement of traf
fi
c that consists of a
green, yellow and red clearance interval.
Cycle –
the total time to complete one operation
of all phases.
Queue –
is an ordered series of upcoming phases
that are created when vehicles are detected by a
vehicle detector. Each phase in queue will become
active in sequence once the preceding phase is
complete.
Turn Phases:
Protected –
assigns the right-of-way to drivers
turning left and allows turns to be made only
on a green arrow display.
Permissive –
operation requires left-turning
drivers to yield to oncoming (or con
fl
icting) ve-
hicle and pedestrian traf
fi
c before completing
the turn. A permissive left turn is served con-
currently with the adjacent through movement.
Protected-Permissive –
operation represents
a combination of the permissive and protected
modes. Left-turning drivers have the right-of-
way during the protected left-turn phase. They
can continue left turn movements “permis-
sively” when the opposing through movement
receives its circular green indication.
Signal Housings:
High-High –
one traf
fi
c light is positioned
5.2m (17ft) above the roadway and the sec-
ondary traf
fi
c light is 5.2m (17ft) above the
shoulder of the road.
High-Low –
one traf
fi
c light is positioned 5.2m
(17ft) above the roadway and the secondary
traf
fi
c light is 2.7m (9ft) above the shoulder of
the road.
2
T
D