5.1.6 Incident Detection and Verification
Detection is the process of collecting data and determining that an incident has occurred and obtaining sufficient information or ‘intelligence’ to determine the appropriate response. A summary of incident detection techniques and their advantages and disadvantages is given in Table 5.2.
|Automatic incident detection (AID) – utilising traffic systems, e.g. CMCS, SCATS, STREAMS, video and Bluetooth‑based systems|
Algorithm software compares traffic data from detectors (loops, infrared, video, vehicle identification, video, Bluetooth) to ‘normal’ traffic. Variety of statistical and analytical methods available, with varying degrees of reliability.
It can also include detection of non-moving vehicles by means of video incident detection.
|Traffic congestion display systems||Congestion displays and alarms can automatically indicate potential incidents.|
|Cameras (CCTV)||Pan-tilt-zoom cameras, at least on major traffic routes and critical locations are particularly important for hazardous locations such as tunnels.|
|Emergency phone call (in Australia 000 or 112 on mobile phone, in New Zealand 111)||Public and motorists report incidents to emergency call centre and are connected to emergency services who subsequently advise the road agency (most common means of detection).|
|Traffic report hotline||Public and motorists report incidents to transport or traffic call centre.|
|Roadside emergency phone||Devices located at regular intervals – usually on major traffic routes only.|
|Incident response units, contracted towing services||Special vehicles or towing services patrol high traffic/ incident sections in peak periods.|
|Police patrols||Peak period patrol on critical high traffic sections.|
|Incident watch||Professional drivers – road agency, taxi, couriers, tow trucks, buses.|
|Mayday||Vehicles transmit distress signal triggered automatically.|
|Aerial traffic monitor||Traffic reporting services use aircraft during peak periods.|
Source: Austroads (2007a).
Much recent research and development work has focused on AID algorithms, primarily applied to motorways (or controlled access roads) and still developing for arterial roads that are much more complex. Automated detection processes traffic data and provides an alarm, allowing an operator to focus on a few events that may be potential incidents. There are a number of different types of algorithms including comparative, statistical, time series and artificial neural network models (which are trained to recognise patterns). The performance of these algorithms is measured in terms of detection rate, time to detect and false alarm rate. Current algorithms result in 90% of incidents being detected with a false alarm rate less than 1% (Austroads 2007a).
Notwithstanding the effort going into automatic incident detection, given the availability of mobile phones, the predominant means of detecting incidents in areas with reasonable levels of traffic is calls from motorists. However, the information from these calls may be inaccurate or incomplete to enable a rapid, effective response.
Incident verification confirms that an incident has occurred, refines information on the location and obtains the best possible information on the nature, extent and severity of the incident to enable an effective response.
Verification of traffic incidents is initially conducted by the relevant emergency services communication centre (i.e. police, fire, ambulance), usually by obtaining advice from the first on‑site responder emergency service personnel. This enables a credible information source that can provide relevant advice on response and access requirements. The disadvantage is that it may take some time for the first responder to get to the scene.
Methods that are used to verify incidents include:
- CCTV in traffic control centres
- field units – police or emergency services personnel at the incident site, incident response unit
- other means including aerial surveillance by traffic report services.
The objective is to verify the occurrence of a traffic incident as quickly as possible, confirm an accurate location and determine the type, extent and severity of the incident so that an appropriate response can be made.
Incident detection and verification: recommended practice
- Develop and maintain strong working relationships with other organisations that have an incident detection capability – primarily emergency services (police, fire, ambulance), but also radio and television traffic reporting services – to ensure rapid provision of relevant information. Establish protocols and agreements on exchanging data and information on traffic incidents.
- Encourage the provision of real-time data on traffic incidents from emergency services computer aided despatch systems.
- Provide detection and surveillance capability across the network to cover locations or corridors which experience high incident rates – vehicle detectors to be able to monitor traffic speeds and flow, software to automatically analyse and alert potential incidents and trigger visual monitoring, CCTV cameras to verify incidents.
- Provide location reference markers at regular intervals (e.g. at 250 m intervals) on high traffic routes to enable more accurate location of incidents and provide more accurate direction for responders. Alternatively, ensure all responders have GPS devices.
- Consider using a number of alternative or complementary detection methods, including automatic incident detection, video detection, use of mobile phones or toll tags as means of providing more accurate, timely traffic data.
- Ensure provision of systems for rapid incident detection in tunnels. In major tunnels consider multiple systems, e.g. automatic incident detection and video detection and verification.
- Provide traffic and incident information to emergency services, e.g. provide video feed from cameras to police communications and crash investigation units, provide electronic real-time congestion maps to emergency services to enable them to determine less congested access routes.
- Deploy incident response services in high incident times and locations, to also act as first responders and provide detection and verification information to traffic and emergency control centres. Ensure quality communication channels are available which can include radio, phone, wireless Internet (video, email), pagers, and mobile video cameras for responders.
- Build a ‘traffic incident watch’ capability with road agency staff, police patrols, and professional driver groups such as taxi, bus and truck operators.
- Educate the travelling public about how and what to report on traffic incidents – provide a traffic hotline which can also provide up-to-date traffic reports.
- Actively seek innovations to reduce the time to detect and verify traffic incidents including time taken to be notified by emergency services. Monitor and report time taken to detect and verify incidents.