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BACKGROUND
Obtaining accurate and timely traffic data is essential to successful transportation
operations/planning projects. Several methods of collecting traffic data are available, which
range from manual counts by field personnel, to using different technologies designed
specifically for data collection (such as road tubes, video detection, induction loops, radar, etc.).
Traffic detection technologies can generally be classified into two groups: intrusive and non-
intrusive. Intrusive detection technologies are installed on/within the roadway. These
installations require lane closures, which disrupt traffic flow and increase vehicle-personnel
interactions. Using this type of technology is inherently more hazardous and is generally more
time consuming, especially for temporary traffic data collection. Non-intrusive traffic detection
technologies are deployed adjacent to the roadway and require minimal (if any) interaction with
traffic flow. These types of detection technologies do not require any lane closures, which
results in a safer environment.
Several studies have been performed comparing different types of non-intrusive technologies.
Radar based detection devices have consistently scored the highest in accuracy, cost-
effectiveness, and installation/use [1, 2, 3]. The Advanced Traffic Analysis Center (ATAC) has
acquired several radar-based traffic detectors and will evaluate their performance for the North
Dakota Department of Transportation (NDDOT), specifically for use as temporary data collection
devices.
STUDY OBJECTIVES
The main objective of this study is to determine the applicability of using radar-based sensors to
support the NDDOT traffic data collection efforts. These sensors would be used primarily as
temporary, portable data collection devices, so ideally they would be deployed with minimal
resources.
During the study, the sensors will be evaluated for accuracy in providing volumes, speed, and
classification using two types of mounting methods. The first method consists of a tripod-based
system which was designed and built by ATAC staff. The second method consists of mounting
the sensors to an existing sign structure.
This study will also provide documentation on setting up and calibrating each of the sensors to
improve accuracy. The configuration and calibration guides for each sensor are located in
Appendix A. During the study’s kick-off meeting on June 17, 2008, the format of the sensors’
output files was a concern for the NDDOT. Currently, all of NDDOT’s traffic data are stored as a
.PRN file type, which has a much different format than the sensor output files. As a result, this
study also will develop an Excel spreadsheet to converts each of the sensor outputs into the
.PRN format.
RADAR SENSORS
Radar sensors operate by focusing a radar beam primarily perpendicular to the roadway, and
detecting the reflection from vehicles as they pass through the beam. The radar beam tries to
emulate an inductive loop by detecting the presence, size, and speed of vehicles. Since the
detector only sees the signature of the vehicles passing through its beam, it bases the
classification on the length of the vehicle being detected.
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