The smoothness of pavements before a location where weigh-in-motion (WIM) equipment is installed is known to affect the accuracy and operation of the equipment. Current ASTM WIM smoothness specifications require closure of the traffic lanes. The proposed project would use high-speed profile equipment measurements to determine acceptable ranges of smoothness that are essentially equivalent to the ASTM method. The proposed specification is an enhancement to the FHWA's States' Successful Practices Weigh-In-Motion Handbook. The project will also include a review and consideration of new technologies and measurement devices outside of the LTPP.

Traffic loading and vehicle classification measurements are key elements in pavement analysis and performance prediction. Highway agencies are investing increasing sums in WIM equipment to provide this information. Existing smoothness specifications are difficult to implement. Lack of smoothness creates difficulties in calibrating equipment, and is thought to be a leading cause of poor performance of WIM equipment. Decreasing smoothness may be a contributing factor to scale drift and increasing variability of load data. The guideline would provide states with a specification for use when installing equipment and reduce calibration and calibration check time. It would also provide a diagnostic tool to use when data changes and decisions on equipment reinstallation and/or pavement correction are required.

Status: The panel decided to have this work be handled by FHWA LTPP staff. FHWA will be responsible for this work; funds were transferred to FHWA.