The SCATS system, reputedly the first fully traffic-adaptive system in the world, was developed in the 1970's in Sydney, Australia, and installed throughout Melbourne progressively from 1980. Melbourne, Australia's second largest city and Victoria's capital, has a population of 3.4 million and is spread over an area of approximately 1700 square kilometres. There are over 2,800 sets of traffic signals in Melbourne, of which 2,400 are on arterial roads and connected to SCATS. SCATS differed greatly from the more generally used fixed time systems in that traffic management was no longer based upon rigid time of day/day of week patterns. SCATS is able to adjust its traffic control parameters in accordance with the traffic demand as measured in the street via loop vehicle detectors mounted in the road surfaces at each stop line. Its mechanism of adjustment is through variation to Splits (Proportion of Red, Green) Cycles (Time between successive Greens and Offsets (delay between Greens at successive junctions). Thus instantaneous changes in traffic demand due to incidents could be automatically handled by the system. Such incidents might include motor accidents, major sporting events or an unexpected drastic change in the weather causing hundreds of beach patrons to return home hours before normal expectations.
Abstract