Table of Contents

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.

Table 5.2: Incident detection/verification techniques

Detection method Description Advantages Disadvantages
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.

  • Automatic detection – alarm system provides decision support.
  • Need coverage of detection devices (loops at say 500 m on freeways).
  • Balance time to detect, with detection rate and false alarm rate.
  • Need to verify using camera or other means.
Traffic congestion display systemsCongestion displays and alarms can automatically indicate potential incidents.
  • Utilises existing infrastructure for traffic control.
  • Need coverage of detection devices (loops at say 500 m).
  • Need integrated system, using information from traffic system, ramp metering, etc.
  • Need to verify using camera or other means.
Cameras (CCTV)Pan-tilt-zoom cameras, at least on major traffic routes and critical locations are particularly important for hazardous locations such as tunnels.
  • Readily able to verify incidents (also able to monitor traffic).
  • Can use video detection.
  • Cost of equipment, communications.
  • Impossible to monitor every camera manually.
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).
  • Low cost (to road agency).
  • Operate 24 hours every day.
  • Can verify incident when multiple calls received.
  • Quick advice about incident in high traffic areas, usually less than one minute in peak traffic periods.
  • Depends on public calls – for most serious incidents the number of calls is very high.
  • Usually need to verify information to clarify location, severity and extent.
  • Need call centre to provide timely information to road agency – either voice, fax or electronic.
  • Multiple call centres, e.g. police, fire, ambulance – require coordinated information.
Traffic report hotlinePublic and motorists report incidents to transport or traffic call centre.
  • Fast detection.
  • Can verify incident when multiple calls received – plus can use CCTV if available.
  • Relatively economic detection process as call centre has multiple uses.
  • Need to operate in high traffic periods, preferably 24 hours every day (resourcing implications).
  • Depends on public calls to traffic hotline (education).
  • Need to verify and improve quality of information, clarify location, severity and extent.
  • Multiple call centres, e.g. police, fire, ambulance, traffic getting same/ different information.
Roadside emergency phoneDevices located at regular intervals – usually on major traffic routes only.
  • Clear purpose – direct connection to call centre.
  • Accurate location of phone known.
  • Available 24 hours every day.
  • Depends on public calls.
  • Usually need to verify information to clarify location, severity and extent.
  • Need call centre to provide timely information to road agency – either voice, fax or electronic.
  • Cost to install/ maintain – becoming less used with proliferation of mobile phones.
Incident response units, contracted towing servicesSpecial vehicles or towing services patrol high traffic/ incident sections in peak periods.
  • Detect and verify by credible source.
  • Provide timely intelligence enabling appropriate response.
  • Early response – able to fix minor incidents.
  • Resourcing implications of funding incident response services – time and areas able to be patrolled depends on ongoing commitment of resources.
  • Traffic congestion limits access for services.
  • Responder safety issue for response services on high speed roads.
Police patrolsPeak period patrol on critical high traffic sections.
  • Detect and verify by credible source.
  • Provide timely intelligence.
  • Quick access.
  • Early response.
  • Recognised authority by motorist.
  • Resourcing implications of funding special service.
  • Responder safety issue on high speed roads.
  • Difficult access in congested conditions.
Incident watchProfessional drivers – road agency, taxi, couriers, tow trucks, buses.
  • Informed sources.
  • Wide coverage of the road network.
  • Need education to engender useful level of response.
  • Still need verifying depending on credibility.
MaydayVehicles transmit distress signal triggered automatically.
  • Automatic.
  • Fast.
  • Accurate location (GPS).
  • Limited deployment – currently only in high end vehicles or consumer paid service.
  • Private call centre needs to relay message.
Aerial traffic monitorTraffic reporting services use aircraft during peak periods.
  • Broad coverage.
  • Able to review trouble spots.
  • Commercial interests.
  • Limited to peak periods only.

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.

  • 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.