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6.7.10 Controller Programming

The task of configuring a controller to the specific requirements of a particular site is known as adaptive engineering. Each controller has a unique program called a ‘personality’ which configures the controller to the specific operational design of the intersection or mid-block device it is controlling. Traffic signal controllers can also be configured to control overhead lane signals, ramp signals and signals associated with roundabouts.

Where two devices are very closely spaced, there can be advantages in using one controller for both devices, provided the controller has sufficient signal groups. This reduces installation and recurrent costs, and guarantees traffic progression (offsets) between the two devices, but increases the complexity of the personality and detection problems may be encountered if detector feeder cables are excessively long (over 100 m).

The personality specifies which signal groups run in each phase, the sequence of phases, detector functions, detector alarm conditions and default time settings. Signal groups can be controlled conditionally within a phase, e.g. in a diamond overlap phase or completely independently of the phasing, e.g. slip lane vehicle and pedestrian groups. Where there are unusual operations, such as a railway interlink, the personality logic can be quite complicated.