"This report contains the findings of a study that was performed to establish the variablity of Chappy V-notch (CVN) impact toughness within plates of A572 Grade 50 and A588 steels. The study included plate thickness up to 4 inches meeting AASHTO Zone 3 fracture notch toughness requirements. Both existing literature and the results of research conducted for this study were examined in an attempt to define the variablity in CVN values. The report provides a comprehensive description of the research, including a discussion of the statistical analysis methods used, along with recommended revisions to the AASHTO Guide Specifications for Fracture Critical Non-Redundant Steel Bridge Members. The proposed revisions are intended to provide a reasonable certainty of safe and effective performance of steel plate with respect to toughness. The contents of this report will be of immediate interest and use to bridge engineers, materials engineers, steel bridge fabrication, specification writing bodies, researchers, and others concerned with the design and fabrication of steel bridge elements." --from foreword.