Interface with adaptive traffic control systems


The ITS systems of the Public Transport Operator or Authority (‘transit system’) can interface with the Traffic Control Systems of the Traffic Authority (‘traffic system’). Such interfaces:

  • allow one or both systems to access information that their own systems do not provide
  • allow one of both systems to supplement their own information with additional detail
  • support combined services

The main uses and applications supported by interfaces between the transit and traffic systems are:

  • Traffic system supplies data about traffic speeds which the transit system uses:
    • Historic speeds and variances for links and route sections, which the CAD/AVM includes in its reference database
    • Current speeds and variances, which the CAD/AVM system includes in its active operations management
  • Traffic system supplies data about disruptions, diversions, roadworks, etc. which the transit system uses in both the CAD/AVM, and in Traveller Information Services
  • Traffic system provides access to street-side CCTV, so that CAD/AVM dispatchers can view actual events on important streets, junctions, stops, and potential delay/disruption points
  • Transit system provides information about public transport service speeds and variance, which the traffic system uses:
    • Historic speeds and travel times, and their variances for route sections and links, which is used to calibrate the traffic network model, signal plans (e.g. Transyt)
    • Current speeds and travel times for route sections and links, which are analysed as ‘probes’ for the adaptive traffic signal control system
  • Transit system provides information about network, routes and turning movements, which the traffic system uses to calibrate traffic signal priority algorithms and rules
  • Traffic system provides priority for public transport vehicles at traffic signals, in some cases using location and status data provided by the transit system
  • Transit system provides real-time traveller information and event/incident information to traffic system for dissemination through their travel advice channels
  • Transit system provides direct feed of real-time vehicle locations and/or forecast arrival times at stops (derived from CAD/AVM system), in cases where traffic authority has responsibility for real-time traveller information systems

Technologies, data and resources

The information exchange and shared services are based on existing systems and devices. In general no new systems are required. Communications links may need to be established or upgraded, and there may be implications for servers and data storage capacity.

Interfaces need to be specified and tested. Most modern transit and traffic systems already provide for data export and exchange both internally and to external systems. With more open and less proprietary systems, many suppliers already include the capacity to interface with the more well-known systems of other suppliers.

Advantages and Cautions

The primary advantages of Interfacing Transit and Traffic ITS systems are to:

  • Expand and enhance the information available to both systems
  • Improve the calibration and effectiveness of traffic and signal control systems
  • Support additional or enhanced services
  • Increase the number of users of various systems and software, thus increasing the benefits of the investment
  • Facilitate co-ordination among the transit and traffic teams to resolve traffic problems
  • Share detector, communications links, etc. costs

The principal cautions in relation to interfaces between Transit and Traffic systems are:

  • Interface between these systems is a long-haul process, which probably begins with a few specific data exchanges or a common service, and over time expands to something far more significant. A structured approach needs to be developed, ideally based on common or compatible system architectures.
  • Good working relationships are required between the transit and the traffic authorities
  • Specialist capacity needs to be developed within both the transit and traffic system operators who take responsibility for the specification, deployment and maintenance or update of the interfaces. This needs to be properly documented.
  • Corporate memory is important.

Relevant Case Studies

Dublin, Zurich