This report describes how weigh-in-motion (WIM) scales can be used to collect data on truck weights, what uses those data have, and the advantages and disadavantages of using WIM systems to collect the data. The history of WIM development is briefly described, and WIM data needs and uses are reviewed. WIM data requirements are considered, and WIM technology is described. User experiences are presented, and current programs and research are noted.  The report for this topic can be purchased at https://www.trb.org/news/blurb_detail.asp?id=3433