VEHICLES DETECTION

With the current range of detectors most applications which traditionally required inductive loops can be covered with non-intrusive detectors. Expensive road works, disruption of traffic and other unpleasant installation and maintenance aspects of vehicle detection can become a matter of the past.

Intersection Control

Detection of approaching vehicles for request and extension of the green phase in traffic dependent signalled intersections including on-crossing detection of pedestrians. The latest products include multichannel units for time gap recognition, counting or presence detection of vehicles waiting at the stop line and dual technology detectors for special applications and extra reliability.

Traffic Data Acquisition

Counting, speed assessment as well as classification by vehicle length or type for a variety of permanent and temporary applications. PIR and combined technologies detectors can be mounted either above the observed lane or on a pole at its side. Data transfer is by two-way RS 485 bus. Ultra low consumption PIR detectors for solar powered installations are available as well as triple technology detectors for accurate traffic data acquisition including speed and vehicle class.

Tomorrow’s traffic detection requirements ask for easy to use, quickly installed detectors avoiding expensive road works with disruption of traffic during installation and replacement.
Depending on the application ASIM detectors use a variety of detection technologies for optimum performance.

Passive Infrared (PIR)

Passive infrared is detecting the slightest changes of thermal radiation emitted by any object or body having a surface temperature above the absolute zero (-273 °C). The intensity of the radiation depends on the surface temperature, the size and structure of a target but not its colour or the lighting conditions.
By combining dynamic and static sensors with distinct detection areas detectors are available for counting, occupancy measurement, presence detection, queue detection, speed assessment and classification by vehicle length.

Infrared detectors can be divided in two main groups:

- Dynamic detectors react to radiation changes only, a vehicle entering or passing through the field of view activates the output but if the vehicle comes to a stop in the detection area the output returns to its quiescent state.

- Static detectors can hold the presence of a vehicle in the field of view for a time of several minutes and are capable of counting.

Doppler Radar / Microwave (MW)

Microwave detectors emit focused high frequency signals within a specified frequency band in the GHz region. A vehicle moving into or through the detection area reflects the signals back to the detector. From the Doppler shift between the emitted and received frequency the direction and speed of a vehicle can be determined very accurately.
Doppler radar detectors are dynamic and react to motion only.

Ultrasonic (US)

Ultrasonic detectors emit high frequency acoustic signal bursts beyond the audible range of humans and most animals. A vehicle moving into or through the detection area reflects the signals back to the detector. The distance to the surface of a vehicle is measured from the travel time of the ultrasonic bursts. As a result of this active ranging, a highly reliable presence detection of a standing vehicle for a virtually unlimited time, counting and classification are possible.

Combined Technologies

By combining two or more technologies in a single detector a wide range of optimised detectors for a large variety of applications becomes possible. Such products are particularly useful in traffic data acquisition applications.