State highway agencies need accurate truck-weight data for use in planning, design, operations, and maintenance activities related to both highway pavements and bridges. A considerable amount of data is needed to support these activities, as well as for enforcement and highway finance purposes. Various weigh-in-motion systems are available to collect truck data in a more efficient manner than by using conventional weighing methods. A number of states are currently installing these systems and are specifying and conducting independent acceptance and validation procedures. However, nationally recognized procedures for acceptance testing and for on-site calibration of WIM systems do not exist. Such procedures need to be developed and validated by statistically designed field experiments so that WIM users can be confident that WIM-estimated weights will meet specified tolerances for various applications. Widely accepted procedures will also benefit the manufacturers by providing more consistent testing requirements among their customers. The objective of this research is to develop a procedure(s), covering all WIM system applications, for (1) acceptance testing, (2) on-site calibration, and (3) periodic verification of system performance.

The project began with a review of past experience and technical information relating to the evaluation and calibration of WIM systems. Recommended procedures for evaluation and calibration of WIM systems were developed for acceptance testing, calibration at time of installation at each site, and periodic verification. Factors considered included (1) types and applications of WIM equipment, (2) site conditions, (3) traffic mixes, and (4) requirements for a statistically valid traffic sample for each site. A prototype non-destructive testing device for field testing and calibration of WIM systems was developed based upon a falling weight deflectometer. This device was field tested under different conditions to support the WIM testing procedures at a number of locations in different states. The results of these efforts are documented in the final report.

Status: Research has been completed, but a decision was made not to publish the final report. It was used to initiate a continuation phase for further validation under NCHRP Project 3-39(2). The contractor's final report is available from the NCHRP.