Safety is a major concern for tunnel operators. Local authorities responsible for tunnel facilities are concerned with developing restrictions for hazardous materials passing through the facility that will reduce the risk of death and injury, to an extent that these restrictions do not burden commerce unnecessarily. Hazardous material regulatory controls for tunnels are extensive, detailed, and subject to constant changes. The general lack of expertise in tunnel personnel and the lack of a scientific basis leading to the development of these regulations have created problems to local tunnel authorities when updating the restrictions, or when faced with new materials introduced by the industry. Traditionally, most regulatory restrictions enforced both at the federal and the local level are based exclusively on subjective estimation by a panel of experts and on political influence. Experts, however, are not readily available and are expensive to maintain. The need for immediate decisions has constrained tunnel operators to rely on their own intuition in addressing real time transport safety problems in tunnel facility. To address some of these problems, this research investigates the application of knowledge engineering tools to develop a consultative regulatory control system. Specifically, this study presents a structural framework for developing a knowledge-based expert system as an aid to decision-making in tunnel transport safety. The regulatory problem is modeled as a classification type of problem, which lends itself neatly to an expert system application. Heuristic problem solver which is commonly used in solving classification problem involves the systematic matching of the attributes of an unknown entity to a set of pre-defined solutions. For this study's application, the regulatory groupings inherent in existing tunnel regulations are the basis for developing the solution space. The computer program developed uses knowledge which specifies the appropriate regulation applicable to a new commodity based on the material's physical and chemical properties. / M.S.