This paper describes the structure and development of a prototype interactive web-based decision support system (DSS) for land-use planning applications. The DSS also provides an educational tool for chemical and environmental engineering students in design, risk management and environmental control courses. The DSS is developed on the basis of a hierarchical systems perspective, allowing users to be guided in their decision making process or alternatively to enter the system at various levels depending on their expertise. The DSS incorporates a number of key features such as advice and information on the handling, storage and control of dangerous substances in different development categories. It incorporates both shortcut charts and detailed, interactive calculations to assess effects of fire, explosion and toxic release. These facilities provide primary information for control and siting purposes. Other features allow the user to investigate good engineering design principles to be incorporated into facilities as well as the use of inherently safer designs. The DSS has been supported by local planning authorities and an oil refining company and is undergoing constant use and expansion.