Piezoelectric sensors for weigh-in-motion systems: An experimental insight into edge effects

Experimental campaigns conducted on the theme of weigh-in-motion exhibited an unexpected scattering of the weight measurements. In spite of several attempts, no argument was found to satisfactorily explain the dispersal, in particular for the sites implementing piezoelectric sensors. After tackling this problem numerically in a previous study, the present investigation aims at understanding experimentally the behavior of such systems within the material in which they are embedded in the road. A field campaign utilizing an instrumented truck confirmed a loss of sensitivity at the ends of the sensor. This result was also corroborated by laboratory testing on a servohydraulic jack. It is shown that the location of a load over the sensor affects its response, and that only a small part of the traffic lane is saved from edge effects. The major mission of this work is to make users of weigh-in-motion systems based upon piezoelectric sensors aware of this phenomenon so that they can take actions to recognize and compensate for the potential measurement errors associated with using this type of sensor.