DEVELOPING MEASURES OF EFFECTIVENESS FOR TRUCK WEIGHT ENFORCEMENT ACTIVITIES

This research addressed the determination of what is actually accomplished as the result of truck weight enforcement efforts. One project objective was to develop and validate truck weight enforcement measures of effectiveness (MOEs). Traditionally applied measures, e.g., numbers of trucks weighed and citations issued, have simply provided indications of enforcement effort. These measures failed to provide results in terms of real enforcement objectives, e.g., to deter overweight trucks and minimize pavement wear and tear. MOEs were developed in this project via a series of analytical procedures. They were subsequently validated in a comprehensive four-state field evaluation. Matched weigh-in-motion (WIM) data sets, collected under controlled baseline and enforcement conditions, were analyzed to determine the sensitivity of candidate MOEs to actual enforcement activity. Data collection conditions were controlled in order to avoid contamination from hour-of-day, day-of-week, and seasonal effects. The following MOEs were validated on the basis of their demonstrated sensitivity to truck weight enforcement objectives and the presence of enforcement activity: (1) Severity of Overweight Violations; (2) Proportion of Overweight Trucks; (3) Average ESALs (equivalent single axle loads); (4) Excess ESALs; and (5) Bridge Formula Violations. These measures are sensitive to legal load-limit compliance objectives of truck weight enforcement procedures as well as the potential for overweight trucks to produce pavement deterioration. A second project objective was to document findings in a user guide formatted to explain appropriate data collection methods, how to apply these methods, and how to interpret their results. A software User Guide was developed which statistically compares calculated MOEs between observed enforcement conditions. It also conducts an automated pavement design life analysis estimating the theoretical pavement-life effect resulting from the observed enforcement activity.