The Sydney coordinated adaptive traffic (SCAT) system philosophy and benefits

Sydney, Australia, just as many major cities in the world, has seen traffic movement become more and more congested despite capital expenditure on road construction and widening, on public transport systems, and on traffic management measures. SCAT, the coordinated adaptive traffic signal system, now being installed in Sydney, offers a substantial improvement to movement on arterial roads at low cost thereby enabling usage of the arterial road network to be optimized. An initial trial on a length of arterial road showed advantages in journey time over optimized fixed-time signal coordination of 35-39 percent in peak periods. SCAT is unique in that it consists entirely of computers and is totally adaptive to traffic demand. Its communication network provides extremely powerful yet flexible management of the system. The system, the system philosophy, and the benefits it is expected to yield are described. The benefits are not only in reduced delay, improved flow, and decreased congestion, but also in reduced accidents, lesser usage of petroleum resources, decreased air pollution, and improved residential amenity.