RTI used an interdisciplinary approach in its analyses of the petition review process, combining systems analysis, operations research, economics, toxicology, chemistry, environmental science, and data quality analysis. A taxonomy of the process was developed. Information was gathered on the types of personnel, level of effort by personnel type, and any other resources required. Petitions were classified into tiers depending on the amount of review material submitted and the overall estimate of review duration. This information was combined with information on petition classification, work units, and resource requirements. Software tools were developed to use and display this information to show where backups in petition processing occur and their possible causes. It also provided information on resource use by highlighting over- and underused resources.