To develop guidelines for rest-area wastewater-treatment systems that are capable of complying with the requirements of public Law 92.500, the principal treatment situations encountered at rest areas have been identified. The quantity and quality of wastewater produced at rest areas were examined through a literature survey and through visits to various state highway departments. The common categories of wastewater-treatment systems in use at rest areas are discussed, and their capability for compliance with the requirements of Public Law 92-500 was investigated. An extended-aeration, activated-sludge plant was shown to be capable of meeting these requirements. Initital results of the study indicated that lack of adequate design criteria results in major problems in planning, designing, and operating test-area wastewater-treatment facilities. To meet this deficiency, new design criteria and operation guidelines were developed to assist the state highway departments responsible for providing and maintaining wastewater-treatment facilities at rest areas./Author/