Improvements in Piezoelectric Sensors and WIM Data Collection Technology

Weigh-in-Motion (WIM) technology has been applied in traffic monitoring and weight enforcement, pavement design protocols, pavement management, and transportation safety for approximately fifty years. In September 2007 three types of WIM piezoelectric sensors (ceramic, polymer and quartz) were installed at the Centre for Pavement & Transportation Technology (CPATT) test site and then evaluated. Surveys of the test site showed that the WIM test site was qualified and met the North American WIM calibration standard ASTM E1318-02. The layout of the three sensors and the differences in their installation procedure are described in this paper and their calibration procedure and performances compared. Comparisons of static weights with the measured weight data for each type of sensor under different test runs, speeds, temperatures and different vehicles, as well as monthly statistical analyses of the three types of sensors, were completed. To better understand the inherent performance of the sensors, a data acquisition system was also introduced for raw signal collection. The objective of this paper is to report in detail on preliminary evaluation results from this installation and to make suggestions based on these results for low cost improvements in piezoelectric WIM technology. The evaluation verified that the piezoelectric quartz sensor technology has the best weight measurement accuracy, non-sensitivity to temperature change, and an overall best performance among these three sensors. Therefore, the quartz sensor was also chosen for the Ontario Ministry of Transportation (MTO) Hwy-401 LTPP project for field data collection and further research. However, this performance comes at a higher cost than the other sensors. Research is being directed forward to improve the other sensors’ performance with inexpensive auto-calibration methods based on temperature, vehicle class, and speed adjustments.