Predictive and real-time information about traffic conditions and travel times contributes strongly to the improvement of traffic efficiency. It enables road operators to understand how well the road network is operating, and enables the timely detection of incidents. For example, a TCC may wish to measure the performance of its road network to provide tangible evidence that the methods to reduce congestion and improve the consistency of journey times are having a positive effect. Visualisation of the state of the road network at the TCC, interpreted from a network of static and mobile detectors, is critical. (See Traffic & Network Status Monitoring)
Traffic and network status monitoring activity involves:
Effective traffic and road network status monitoring depends on a combination of static detectors, Closed Circuit Television Cameras (CCTV) and ad-hoc reports of unplanned incidents. Ad-hoc sources include the police, road authorities, vehicle breakdown organisations and public transport operators. (See Other Monitoring Sources) The TCC will use the data to monitor traffic, manage incidents and monitor weather and road surface conditions. (See Operational Activities and ITS & Road Safety)
CCTV cameras have traditionally been a source of real-time traffic information and the means for Traffic Control Centre (TCC) operators to validate reported incidents. The operator also needs to be presented with a general view of the road network which draws attention to information relevant to the operator’s task. This could include traffic flow, occupancy, queue length, equipment status and messages that are presented to road users by Highway Advisory Radio (HAR) and Variable Message Signs (VMS). The public sector or third parties are generally responsible for data collection and its aggregation – whilst users of the information will include the TCC operators, other stakeholders and the general public - as shown in the figure below.
The same combination of technologies (hardware, software and computer graphics) will also provide the means to configure and update traffic plans and manage voice communications with the TCC (such as telephone call set-up and recording), reporting, organisational performance management and operator training. (See Operational Activities)
Many technologies provide the basis for systems to monitor traffic levels and determine the real-time performance of a road network. (See Vehicle Detection and Probe Vehicle Measurement) The systems aggregate the data and make them available to the TCC operators and for Automatic Incident Detection (AID) systems. (See Automatic Incident Detection (AID)) Typically the components required for a highly reliable, fault-tolerant and flexible system architecture at the TCC - for the purposes of information collection, storage and presentation - may be split into four categories:
The TCC will also be equipped with telephone (conventional circuit-switched or Voice over Internet Protocol) and a Private Mobile Radio (PMR) system.
The key to successful traffic operations is inter-agency cooperation and coordination – for example between the TCC and other stakeholders such as the emergency services, major vehicle fleet operators, ports, airports and rail stations. (See Interagency Working).The extent of inter-agency cooperation has a major impact on the TCC’s operations and the support systems required. Integration can be facilitated by co-locating stakeholders in the TCC – as happened during the London Olympic Games.
When a new TCC is being planned or an existing TCC is being upgraded – it is important that the TCC system architecture (including the collection of traffic data) is aligned with the requirements of core applications. This is– usually split between highway management and arterial route management. These are often the responsibilities of different agencies but in future more integrated solutions may become available. (See Regional networks)
The system architecture should be designed to enable more efficient TCC operations at lower cost. For example, as the complexity of the network monitoring infrastructure expands, the architecture should provide for greater use of automated system health monitoring. This ensures that the TCC and field equipment are performing their expected functions properly. (See What is ITS Architecture?)
The use of proprietary interfaces for vehicle detection and traffic monitoring systems can increase the cost of expansion and increase the dependency on a small number of technology vendors and system integrators. Requiring standards-compliant interfaces can help retain supplier independence for the road operator – providing the requirement generates a market response. (See ITS Standards)
Any changes to a system needed to accommodate technology innovations is likely to impact on maintenance and operator workflow - requiring training, a revision to documented procedures and potentially – opportunities for innovation. For example, the use of a Knowledge-based Expert System (KBEST) to provide recommendations to TCC operators on traffic plans, is an innovation that can improve the efficiency of staff having to monitor several routes simultaneously. (See Future Trends)
CCTV cameras can help monitor traffic conditions, detect incidents, validate them, monitor the emergency services and help manage incident clearance. In some applications, 80% of incidents are detected with CCTV cameras – although their performance is compromised at night on routes without artificial lighting. CCTV cameras can be subject to vandalism and their communication cables subject to theft, even if optical fibre cables are used. TCC operators may wish to transfer some of the upgrade and operating risks to third parties (see box on Design, Build, Operate and Maintain - below). The involvement of third parties in data collection and data analysis (on an availability payments basis) can replace the need for expensive investment in additional network monitoring infrastructure.
Design, Build, Operate and Maintain
The South African National Roads Agency (SANRAL) awarded a Design Build Operate and Maintain (DBOM) contract to a single contractor who was responsible for the refurbishment and upgrading of regional TMCs. This included the addition of new traffic monitoring infrastructure, its maintenance, operations and coordination with communication service providers and emergency service providers (Case Study - ITS Design & Operating Services, South African National Roads Agency (SANRAL) (South Africa)).
Pressure on TCCs is higher than ever before in the face of:
Traditionally, vehicle detection and traffic monitoring systems lacked the capability to perform data error correction, data analysis, self-diagnostics and reporting. As the capability of these systems has improved, more data needs to be exchanged with the TCC – and health monitoring may be centralised at the TCC.
In practice, each function of a TCC relating to network monitoring can be upgraded separately. This can be facilitated by dividing the TCC into functional modules and developing upgrade requirements for each: