Sydney Coordinated Adaptive Traffic System (SCATS)
SCATS (27,28) was developed by Australian researchers. It is similar to SCOOT and is
considered to be an adaptive control method between first-GC and second-GC (17). A
major difference between SCATS and SCOOT is that SCATS does not have a traffic
model or a traffic signal control plan optimizer. SCATS selects the best phase durations
and offsets from some predefined plans (17) based on real time traffic flow conditions.
SCATS has a hierarchical system structure, which has three levels as shown in
Figure 6. The lowest level consists of the local controllers at each signalized intersection.
They perform tasks such as data collection, data preprocessing, and assessment of
detector malfunctions. In the middle level are the regional masters, which are the core of
SCATS. Each regional master controls up to several hundred local controllers, and these
controllers are further grouped into systems and sub-systems. Sub-systems usually
consist of several intersections and are the smallest control element on multi-intersection
level. The highest level is the control center, which does not really perform any specific
control operations. The purpose of the control center is mainly to monitor the entire
system.