This paper describes an experimental study comparing the accuracy of weigh-in-motion (wim) scales and piezoelectric cables (piezo). The axle loads measured by the wim and the piezo are compared to thedynamic axle load measurements obtained with the instrumented vehicle developed by the vehicle dynamics lab of the national research council of canada. The experiment was carried out in october 1987 at the instrumented pavement site constructed by the ministry of transportation of ontario on highway 7n north of toronto. The site is equipped with a variety of sensors, including one conventional, platform-type wim scale and five piezoelectic sensors. The experiment involved three levels of vehicle speed (40, 60, and 80 km/h), two levels oftire inflation pressure (80 and 100 psi), and two suspension types (air and rubber). Three replicate runs were performed for each combination of variables. The longitudinal placement of the vehicle with respect to the sensors was determined with a laser beam-based axle detector. Analysis of the accuracy of individual sensors revealed that only two of the piezo cables were sensitive with respect to tire inflation pressure, while none was sensitive with respect to vehicle speed. The average accuracy of the wim scale was on the order of 6%, while the accuracy of the piezo cables ranged from 6 to 12%. Pairedcoparisons of the accuracy of each of the piezo cables to the accuracy of the wim scale revealed that one of the piezo cables is comparable to the wim scale while the other four are less accurate than the wim scale. Considering the variation involved, however, only one of the piezo cables was shown to be significantly less accurate thanthe wim scale. This paper appears in transportation research recordno. 1215, Pavement management and rehabilitation.
Abstract