Sydney Coordinated Adaptive Traffic System

Default operation The architecture of SCATS is at two basic levels, Tactical control (local) and Strategic control (regional, known as MASTER). 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 previously operated this way. Other factors impacting pedestrian access include the number of opportunities in the cycle when pedestrian can cross (often one), and pedestrian demands not being recorded in time for action by the signal controller. The SIDRA User Guide states when pedestrians have to wait 20 or 30 seconds (average delay per pedestrian) the delay is noticeable. When the delay is 30-40 seconds there is an increased likelihood of risk taking as the delay is irritating. Risk taking behaviour is likely with a delay of 40-50 seconds and above 60 seconds there is a high likelihood of risk taking as the delay exceeds tolerance level. Longer or more frequent green signals for pedestrians can reduce unsafe crossing by 34%. 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. ==SCATS Ramp Metering System==

The SCATS Ramp Metering System (SRMS) is a SCATS subsystem and controls traffic signals at the entries of motorways and integrates with SCATS intersection control for promoting integrated real-time management of the traffic corridor as a whole. The objective of SRMS, based on current traffic conditions, is to efficiently determine: • When ramp metering signals start and end ramp metering operation • The metering flow rates of the operating ramp metering signals • Which actions shall be taken to signalised intersections of the corridor to promote network-wide benefits. SRMS achieves these objectives by implementing a collection of pre-configured adaptive intelligent strategies either automatically or manually. In manual mode, the SRMS operator can create new or manipulate existing rules in order to adjust the ramp metering system for effective operation during any planned or unplanned events (e.g. incidents). SRMS is a distributed control system that operates on a central control server and road-side traffic controllers. The central control server is a component of SCATS and inherently provide integrated motorway and arterial real-time management. The road-side controllers are installed on motorway on-ramps and are used to: • Set the traffic signal times • Set the state of on-ramp changeable signs • Manage the sequences start and end ramp metering operation; and • Measure traffic states using vehicle detectors. Metering rates are determined by the local traffic signal controller or by the central control server. Metering rates can be determined in two ways: • adaptive operation, or • time-of-day-based operation typically when a communications failure or critical vehicle detector failures take place The adaptive operation optimises mainline traffic state by using real-time data from vehicle detector stations installed at several mainline locations, ramps and optionally at arterial roads. The adaptive operation determines control actions at 10 seconds intervals and applies some or all of the following strategies simultaneously: • Coordinated ramp metering • Ramp queue management • Automatic begin and end of ramp metering operation • Variation routines for integration with SCATS intersection control • Variation routines for automated incident responses and unusual circumstances • Manual controls for incident responses and unusual circumstances • Critical lane occupancy calibration • Fault-tolerant strategies • Data logging for performance reporting and off-line analysis SRMS is currently used as the Auckland ramp metering system. ==Simulation==

SCATS can be simulated in-the-loop (SCATSIM) using third party traffic simulation tools. SCATSIM offers an interface supported by Aimsun, PTV VISSIM, Quadstone Paramics and Commuter. SCATSIM offers kerb-side hardware and firmware emulation that interfaces seamless to the SCATS Region and Central Manager offering the same control strategies used in field deployments for both intersections and ramp metering (SRMS). The configuration files prepared by authorities for the Central Manager, Region, SRMS and kerb-side controllers can be re-used without modification by SCATSIM. When Commuter software was acquired by Autodesk, Azalient Ltd support for the Commuter interface was deprecated. Azalient Ltd also developed a plugin that enabled the Quadstone Paramics interface to SCATSIM. This plugin is also deprecated. The Sydney Strategic Travel Model was designed by Hague Consulting Group in 1997. ==History==

SCATS was developed in Sydney, Australia by the Department of Main Roads (a predecessor of Transport for NSW). The commercial SCATS website states SCATS was "established in 1975". The Sydney Traffic Control Centre had a RAMTEK graphics system since 1983, and other SCATS users in Melbourne, Adelaide, Singapore and Shanghai had also installed RAMTEK systems. Production of intersection and regional graphics pictures on PC based graphics systems was operational by 1989, and subsystem pictures would be finished by March 1990. The initial ANTTS network was being installed in 1990, with two thousand tags to be installed in taxi-cabs from February 1991. ANTTS tags are called VIS tags. In 1989 a new algorithm was being coded in the SCATS software. The new method of on-line offset calculation was manually tested on Parramatta Road and showed an 8% improvement over the existing precalculated offset plans. It began to be used in Melbourne in 1982, Adelaide, South Australia in 1982 and Western Australia in 1983. in part of Metro Atlanta, and Cebu City, among several other places. In Hong Kong, SCATS is currently adopted in the area traffic control systems at Hong Kong Island, Kowloon, Tsuen Wan and Shatin. The system may be referred to by an alternative name in a specific installation. However, since deployment outside Australia, New Zealand and Singapore, 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" (Signal Co-ordination for Regional Areas of Melbourne) • Adelaide "ACTS" (Adelaide Co-ordinated Traffic Signals) • Perth "PCATS" (Pedestrian Countdown at Traffic Signals) • Singapore "GLIDE" (Green Link Determining System) • Northern Territory "DARTS" (Dynamic Arterial Responsive Traffic System) ==SCATS Traffic Signal Operation==

===In New South Wales, Australia=== Transport for NSW (TfNSW) is responsible for controlling signals in New South Wales, the same agency which develops the SCATS software. As of November 2025, there were 4860 traffic signals across NSW. In January 2018, Transport for NSW reduced the cycle time for a subset of the Sydney CBD from 110 to 90 seconds. The Lord Mayor of the City of Sydney council wrote to the Roads Minister to request a broader rollout of 90 second cycle times on the 8th of November 2018. As of 2025 WA Main Roads publishes historical SCATS traffic signal phase data under an open source Creative Commons CC BY 4.0 license. Data is published in monthly machine-readable Parquet files. Data includes times for each phase and measured volume. On the TrafficMap website WA Main Roads openly publish Detector Volume Data, Pavement and Signage Drawings, Traffic Signal Arrangement Drawing, Signal Data (including Phase Times, Pedestrian Phase Times, Special Times, Link and Offset Plans, and SCATS Phase History tables) and Phase Sequence Charts for every signal in the state. ===In Victoria, Australia=== The Department of Transport and Planning are responsible for the safety and efficiency of traffic signals throughout Victoria. SCATS was trialled in Melbourne in 1978 and adopted for use throughout Victoria in 1980. In 2018, SCATS controlled more than 4,000 sets of traffic signals across Melbourne and other Victorian rural cities such as Ballarat, Bendigo, Traralgon, Geelong and Mildura. DataVic publish Traffic Signal Volume Data sourced from the detector loops and the SCATS system under an open-source Creative Commons CC BY 4.0 license. Historical data is published back to 2014. Historical Annual Average Daily Traffic Volume data is published from 2001 to 2019 in the GeoJSON format under CC BY 4.0. DataVic also publishes Traffic Signal Configuration Data Sheets, also known as 'operation sheets' or 'op-sheets'. These operation sheets detail signal group and detector functions at each intersection along with the phasing of the site. They include detailed notes outlining the specific operation of signal groups, phases, detectors and general site operation, the traffic signal sequences (phases), and the phase and pedestrian time settings which govern how the site operates. ===In South Australia, Australia=== The City of Adelaide typically has green walk signals in the range of 5-8 seconds. A March 2025 review of signal timing along O’Connell Street in North Adelaide in found that reducing the cycle length could reduce the average pedestrian delay by 14 seconds and allow between 6-21 extra opportunities for people walking to cross during midday peak hour. Reducing signal cycle times was also found to reduce queue lengths and reduce average delays for vehicles by 38-46% in the PM and 50-54% in the midday peak. The Brisbane Times described a benefit of the technology as "motorists will no longer be stuck waiting when jaywalkers have crossed early". The Queensland Transport and Roads Investment Program had a $4.5 million line item for "Smart Crossings project, statewide". By September 2025 the Queensland Government Smart Crossings (SX) Project had installed 112 Smart Crossings at 70 intersections. When radar footpath detectors are used, demand indicators lights (on pedestrian buttons) must be present or installed. For smart crossings, the flashing red (don't walk) time is calculated using 1.0 m/s where slow walking is not expected to be encountered, or otherwise 0.8 m/s. Singapore has a system called Green Man+ which allows a longer green time for elderly pedestrians (over 60 years old) or people with a disability. Green duration is extended by 3 to 13 seconds depending on the crossing width. Identification cards are required to be tapped onto a reader mounted above signal push buttons. Green light duration is otherwise fixed and pre-determined. Green Man+ has been installed at over 1,000 crossings and installation of 1500 more is planned by the end of 2027, ==See also==