3.4.2 Detection Technologies and Telecommunication
Monitoring tools and technologies (or some alternative) are well established and new methods are developing rapidly with advancement of information technology. Components include detection methods, telecommunications and the operations centre. The first two are described in this section, while the operations centre is discussed in Section 4. For more details on detection technologies, refer to the Federal Highway Administration Traffic Detector Handbook (Klein 2006; Klein et al. 2006).
A number of technologies are available for traffic monitoring, some of which may also be used for traffic control and incident detection. Some of these technologies have not been used or have only limited applications in Australia. The technologies include those in Table 3.5. The selection of the most appropriate approach depends on fitness for purpose to match needs and available resources. The key considerations are:
- detection speed
|Inductive loop detectors|
Inductive loops embedded in the pavement to detect the presence or passage of a vehicle.
The most common detector used.
|Magnetometers||Small cylinders containing sensors embedded in the pavement measure traffic volume and vehicle occupancy.|
|Microwave radar, infrared, ultrasonic detection (non-intrusive detectors)||Mounted on a structure above or adjacent to the roadway.|
|Video image detection|
Processes images from camera.
In sensitive to light conditions.
Electronic toll tags have been installed in an increasing proportion of the vehicle fleet.
Provides an opportunity to use probe vehicles as sensors to measure speeds and travel times.
|Automatic number plate recognition||Can be used to measure speeds and travel times and origin-destination.|
|Mobile device location|
Similar in concept to vehicle probes, but using triangulation to monitor vehicle travel speeds.
Bluetooth monitoring technology provides another method of using mobile devices to monitor traffic.
|Bluetooth readers||Readers capture the Media Access Control (MAC) address from Bluetooth-enabled devices in vehicles, which is used to estimate travel times and route choices.|
|GPS tracking||GPS-equipped devices on-board vehicles, such as on busses and trucks.|
Table 3.6 identifies different detection methods that may be applied to network monitoring. Detection methods may be either:
- detectors, including detection technologies appropriate to a function (e.g. inductive loop, magnetometer, microwave radar, infra-red, ultrasonic or video detection)
- ‘non-technological’ methods, which have typically been used for particular functions in network operations projects throughout the world.
Source: Adapted from World Road Association (2003).
Some of the strengths and weaknesses of non-technological detection that should be considered are summarised in Table 3.7.
|Detection method||Description||Strengths and weaknesses|
|Patrol vehicles||In addition to patrol cars, may include other vehicles from various authorities that provide information regarding traffic and road conditions.|
Traditionally has always been an important detection method.
Information is provided by experts thereby greatly increasing the reliability of information from these vehicles.
|Aerial traffic surveillance||Surveillance of traffic conditions from fixed plane aircraft or helicopters.|
Can be provided by the road agencies, or media providing traffic information.
Can provide a good, overall appreciation of traffic conditions over a large area.
|Mobile phone calls from road users||A high percentage of vehicle owners make use of mobile phones. Incidents in both urban and rural areas are reported by this method.|
A very convenient method.
Suffers from the problem of inaccurate information and prank information.
Can also sometimes suffer from an extremely high volume of calls for the same incident.
|Roadside phones||Provision of roadside phones connected to an emergency response centre enables road users to report incidents.|
Mobile phone use is becoming much more popular, limiting need for roadside phones.
Mobile phone coverage may not be available in some locations or road environments.
Source: Adapted from World Road Association (2003).
The major classes of information to be transferred comprise:
- monitored data from the field
- operational commands from the operations centre
- mechanical status information of field devices.
The cost of a telecommunications system can be a significant portion of the overall monitoring system cost. Consequently, telecommunications systems should be carefully selected with the following requirements taken into account:
- types of information to be transferred (data, video, voice information, etc.)
- volume of information (number of field devices, operation commands, etc.)
- communication partners (field devices, agencies, news media, service providers, etc.)
- extent of field data processing
- data format for communication.
Transmitting video information generally requires greater bandwidth. Use of standardised common data formats and telecommunications protocols may reduce telecommunications system costs, facilitate liaison between agencies and aid the future expansion of monitoring systems.