Minnesota Department of Transportation
Building a WIM system around polymer piezoelectric film sensors, called BL sensors, costs only a fraction of the traditional WIM system built around crystalline-quartz piezoelectric sensors called Lineas sensors. However, BL sensors are highly sensitive to temperature, which limits the accuracy of weight measurements. The objective of this research was to investigate the performance of BL sensors head-to-head with Lineas sensors by installing a BL WIM system and collecting data from the same highway. After the test site installation, pavement temperatures were recoded as part of each vehicle record from both Lineas and BL sensor-based WIM stations. The analysis of data collected over 10 months showed that temperature dependency of BL sensors can be removed in terms of average but not variance. More specifically, the average of axle weights after temperature-based calibration was about the same for both BL and Lineas sensors, but the variance was much higher for BL sensors. In conclusion, if BL sensors are used, pavement temperatures must be recorded as part of vehicle records. Then, the weights calibrated based temperature would be as accurate as Lineas sensors in terms of the average but not variance.
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