Evaluation of Weight in Motion Sensors on the IFSTTAR Accelerated Testing Facility

This paper presents an experiment, performed on the IFSTTAR circular accelerated testing facility, to evaluate the performance of different weight in motion (WIM) sensors. This project, carried out with the French ministry of transport, aims at improving the performance of these WIM sensors, to allow automated overload control. Four different types of sensors were evaluated in the project: piezo-quartz sensors (2 types), piezo-ceramic sensors and piezo-polymer sensors. The full scale experiment was performed on a thick bituminous pavement. A total of 10 WIM sensors were installed, as well as other sensors (temperature probes, vertical displacement transducers, geophones). Accelerometers were also used to monitor dynamic load variations. The response of the sensors was evaluated under a wide variety of loading conditions (different loading speeds, temperatures and lateral positions of the wheels). In the first phase of the experiment, the 4 arms of the carrousel were all equipped with single wheels (with wheel loads of 45 or 55 kN). In a second phase, different wheel configurations were tested, on each arm of the testing facility (single wheel, dual wheels, tandem, tridem). A large database, of about 30000 WIM signals, was collected. The full scale tests have allowed to evaluate the repeatability of the different types of sensors, and the influence of different loading conditions (temperature, load type, loading speed..). The results indicate that the sensitivity of the different types of transducers to loading conditions is very different. Recommendations for correcting and improving WIM sensor response have been made.