Sydney Coordinated Adaptive Traffic System
The Sydney Coordinated Adaptive Traffic System, abbreviated SCATS, is an intelligent transportation system developed in Sydney, Australia by former constituents of the Roads and Maritime Services in the 1970s, used in Melbourne since 1982, Adelaide, South Australia since 1982 and Western Australia since 1983. It is also used in New Zealand, Hong Kong, Shanghai, Guangzhou, Amman, Tehran, Dublin, Rzeszów, Gdynia and soon in part of Metro Atlanta, among several other places.
The system may be referred to by an alternative name in a specific installation (except Sydney), although since deployment wider than Australia, New Zealand and Singapore, these localised names do not appear to be commonly used. The following are some local alternative names that have been or are in use:
- Canberra "CATSS" (Canberra Automated Traffic Signal System)
- Melbourne "SCRAM"
- Adelaide "ACTS" (Adelaide Co-ordinated Traffic Signals)
- Perth "PCATS"
- Singapore "GLIDE"
- Northern Territory "DARTS"
In total, about 34,350 intersections in over 154 cities in 25 countries use the system. In Australia, the majority of signalised intersections are SCATS operated (around 11,000).
SCATS primarily manages the dynamic (on-line, real-time) timing of signal phases at traffic signals, meaning that it tries to find the best phasing (i.e. cycle times, phase splits and offsets) for the current traffic situation (for individual intersections as well as for the whole network). This is based on the automatic plan selection from a library in response to the data derived from loop detectors or other road traffic sensors.
The system uses sensors at each traffic signal to detect vehicle presence in each lane and pedestrians waiting to cross at the local site. The vehicle sensors are generally inductive loops installed within the road pavement. The pedestrian sensors are usually push buttons. Various other types of sensors can be used for vehicle presence detection, provided that a similar and consistent output is achieved. Information collected from the vehicle sensors allows SCATS to calculate and adapt the timing of traffic signals in the network.
Public Vehicle priority in SCATS (using data provided from PTIPS) caters for both buses and trams. SCATS has a facility to provide three levels of priority:
- High – In the high priority mode the hurry call facility is used. i.e. the phase needed by the tram is called immediately, skipping other phases if necessary
- Medium (Flexible window) – Phases can be shortened to allow the bus/tram phase to be brought in early. The bus/tram phase can occur at more than one place in the cycle.
- Low – takes its turn. Trams would normally be given high priority, the aim of which is to get the tram through without it stopping. Buses would normally expect to receive a medium level of priority.
The architecture of the system is at two basic levels, LOCAL and MASTER. The LOCAL is the control cabinet at the roadside, which provides the normal signal control as well as processing of traffic information deduced from the vehicle detectors. The MASTER is a remote computer which provides area based traffic control, i.e. area traffic control (ATC) or urban traffic control (UTC). Detailed traffic signal and hardware diagnostics are passed from the LOCAL to the MASTER, with the ability to notify staff when a traffic signal has a fault.
SCATS is able to operate over PAPL, ADSL, PSTN and 3G IP network connections to each intersection. SCATS can also operate on a network of private cables not requiring third party telecommunications support and large parts of inner Sydney have always operated this way.
SCATS is already a recognised worldwide market leader in intelligent transport systems, however the New South Wales Roads and Maritime Services is continuing to develop SCATS to meet emerging technological, user and traffic demands.
In Hong Kong, SCATS is currently adopted in the area traffic control systems at Hong Kong Island, Kowloon, Tsuen Wan and Shatin.
Instant fault detection and quick repair
The ATC system is equipped with the function of fault detection and logging the fault detected in order to facilitate repair and maintenance. Should there be a telecommunication breakdown, the ATC junction controller concerned will switch to standalone mode and continue to function.
Traffic Adaptive Operation
ATC systems provide advanced method of traffic signal control called Traffic Adaptive Control where the operational timing plans including cycle length, splits and offsets are continuously reviewed and modified in small increment, almost on a cycle-by-cycle basis, to match with the prevailing demand measured by the detectors connected to the on-street traffic controllers.
- PTIPS - works together with SCATS to provide transport vehicles with priority at traffic signals
Other Intelligent Transportation Systems include:
- Vehicle detectors to be installed to stop road congestion
- Acott, Kent (6 January 2011). "Red lights that drive you made". The West Australian. Retrieved 18 January 2012.
- ATCS being implemented in Metro Atlanta
- Roads ACT
- Roads and Maritime Services, NSW
- SCATS - Sydney Coordinated Adaptive Traffic System Website
- SCATS - Main Roads Western Australia
- Traffic Lights in NSW - Roads and Maritime Services Website
- RTA and SCATS at the 17th ITS World Congress in Korea
- Review of Bus Priority at Traffic Signals around the World