Sydney Coordinated Adaptive Traffic System

The Sydney Coordinated Adaptive Traffic System , abbreviated SCATS , is an intelligent transportation system that manages the dynamic (on-line, real-time) timing of signal phases to traffic signals , Phase splits and offsets) for a traffic situation (for individual intersections as well as for the whole network). SCATS is based on the loop detectors or other road traffic sensors.

SCATS 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 have inductive loops within the road pavement. The pedestrian sensors are usually push buttons. Various other types of sensors can be used for vehicle presence detection. SCATS to calculate and adapt the timing of traffic signals in the network.

SCATS is installed at about 42,000 intersections in over 154 cities in 25 countries. In Australia, where the system was first developed, the majority of signalised intersections were SCATS operated (around 11,000).


Default operation

The architecture of SCATS 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 traffic control, ie area traffic control (ATC) or urban traffic control (UTC). Detailed information about the MASTER system and its functions.

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.

Priority levels

Public vehicle priority in SCATS (using data from Provided PTIPS ) caters for Both nozzles and trams. SCATS has a facility to provide three levels of priority:

  • High – In the high priority mode the hurry call facility is used. Ie the phase needed by the tram is called immediately, skipping other phases
  • Medium ( Flexible window ) – Phases can be shortened to allow the bus / tram phase to be brought in early. The bus / tram phase can occur 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.

Instant fault detection and quick repair

The ATC system is equipped with the function of fault detection and logging the fault in order to facilitate repair and maintenance. Should there be a telecommunication breakdown, the ATC junction controller will switch to standalone mode and continue to function.

Traffic Adaptive Operation

ATC systems provide advanced method of traffic signal control, whereby the operational timing of cycles and cycles of cycles Measured by the detectors connected to the on-street traffic controllers.

SCATS Ramp Metering System

The SCATS Ramp Metering System (SRMS) [1] is a SCATS subsystem and controls traffic signals to the entries of motorways and integrates with SCATS intersection control for the integrated traffic management of the 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 flows of the operating ramp metering signals
  • Which actions shall be taken to signalized intersections of the corridor to promote network-wide benefits.

SRMS achieves these objectives by implementing a pre-configured adaptive intelligent strategies either automatically or manually. In order to be able to carry out the operation of the system, the SRMS may be used for any purpose. 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 control. Metering rates can be determined in two ways:

  • Adaptive operation, gold
  • Time-of-day-based operation typically when a communications failure or critical vehicle

The adaptive operation optimizes mainline traffic by using real-time data from vehicle detector stations at several mainlines, 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 start and end of ramp metering operation
  • Variation routines for integration with SCATS intersection control
  • Variation routines for automated incident responses and unusual circumstances
  • Manuals for incident responses and unusual circumstances
  • Critical lane occupancy calibration
  • Fault-tolerant strategies
  • Data logging for performance reporting and off-line analysis

Currently SRMS is used as the Auckland ramp metering system .


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 curb-side hardware and firmware emulation That seamless interfaces to the SCATS Region and Central Manager Offering la même control strategies used in field deployments for Both intersections and ramp metering ( SRMS ). The configuration files 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, [2] 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.


SCATS was developed in Sydney , Australia by form constituents of the Roads and Maritime Services in the 1970s. It Began to be used in Melbourne in 1982 [3] Adelaide, South Australia in 1982 and Western Australia in 1983. [4]

It est aussi used in New Zealand , Hong Kong , Shanghai , Guangzhou , Amman , Tehran , Dublin , Rzeszów , Gdynia , Central New Jersey , [5] and soon in-part of Metro Atlanta , [6] 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 alternatives:

  • Canberra “CATSS” ( Canberra Automated Traffic Signal System )
  • Melbourne “SCRAM”
  • Adelaide “ACTS” ( Adelaide Co-ordinated Traffic Signals )
  • Perth “PCATS”
  • Singapore “GLIDE”
  • Northern Territory “DARTS”

SCATS is a recognized worldwide market leader in intelligent transport systems. The New South Wales Roads and Maritime Services is continuing to develop.

See also

  • PTIPS – working together with SCATS to provide transport

Other Intelligent Transportation Systems include:



  1. Jump up^ Aydos JC, O’Brien A.SCATS Ramp Metering: Strategies, Arterial Integration and Results, Proceedings of the 17th International IEEE Conference on Intelligent Transportation Systems, Qingdao, 2014
  2. Jump up^ Commuter Software was acquired by Autodesk
  3. Jump up^ Vehicle detectors to be installed to stop road congestion
  4. Jump up^ Acott, Kent (6 January 2011). “Red lights that drive you made” . The West Australian . Retrieved 18 January 2012 .
  5. Jump up^ [1]Accessed October 13, 2016
  6. Jump up^ ATCS being implemented in Metro Atlanta

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