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There are three basic types of actuated control, each using signal controllers
that are somewhat different in their design:
- Semi-Actuated Control
- Full-Actuated Control
- Volume-Density Control
This type of controller is used at intersections where a major street having
relatively uniform flow is crossed by a minor street with low volumes.
Detectors are placed only on the minor street.
The green is on the major street at all times unless a call on the side
street is noted.
The number and duration of side-street green is limited by the signal timing
and can be restricted to times that do not interfere with progressive
signal-timing patterns along the major street.
This type of controller is used at the intersections of streets or roads with
relatively equal volumes, but where the traffic distribution is varying.
In full actuated operation, all lanes of all approaches are monitored by
detectors.
The phase sequence, green allocations, and cycle length are all subjected to
variation.
This form of control is effective for both two-phase and multi-phase operations
and can accommodate optional phases.
Volume-density control is basically the same as full actuated control with
additional demand-responsive features.
It is designed for intersections of major traffic flows having considerable
unpredictable fluctuations.
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