Road traffic monitoring responds to multiple needs, first of all the increase in traffic safety; the same Highway Code explicitly provides for its creation. It can be included in a wider user information system, taking shape of a necessary and important first phase.
A traffic monitoring system can be considered as an information chain made up of the following parts:
- Sensor: device that produces a descriptive signal of characteristics of the phenomenon to be detected
- Detector: encodes the information detected by the sensor
- Transmission system: transfers the coded information to the central unit
- Treatment system: processes data according to the purpose for which it was collected.
There are two detection methods:
- Manual: detection is performed by a human operator
- Automatic: the detection takes place through an ad hoc systems
For long-term operations, the automatic mode is certainly more suitable as it allows you to collect data in a more reliable and accurate way.
An automatic monitoring system usually consists of four basic components:
A detector, an interpretetion tool, a recorder and a processor.
There are various detection technologies to choose from depending on the purpose pursued.
Generally, the most popular methods are:
- inductive loops
- pneumatic tubes
- triboelectric cables
- magnetodynamic sensors
- microwave sensors
- infrared sensors
- WIM sensors
- acoustic sensors
- video images
- satellite technologies
- mobile equipped units
Monitoring system with inductive loops
An inductive coils is a winding of electric wire, consisting of one or two turns arranged in a square or rectangular shape; electricity passing inside the wire generates a magnetic field which undergoes a variation with the passage of the metal structure of the vehicle; this variation produces an electrical signal that allows the detection of the passage (as well as the characteristics) of the vehicle.
A monitoring system based on these instruments generally consists of one or two coils placed on the sides of the roadway and connected to a detector device. The coils can be installed above the pavement or embedded in the road surface depending on whether the detection system is temporary or permanent.
Currently, this is the most used method. The reasons can be traced to the low costs (mostly related to the installation), the precision of the detections that are not affected by atmospheric phenomena and the long life of the instrument.