Engineering design essentially consists of generating specifications for the artifact being designed. It involves complex tasks of generating various feasible solutions and critically evaluating them. Developing knowledge-based systems (KBSs) requires adopting proper knowledge organization, representation schemes and suitable problem-solving techniques, which depend on the nature of the design task and type of knowledge involved. This paper presents one such exercise carried out in the domain of bridge engineering design. A design process model, comprising of rule-based inference, solution generation (synthesis) and evaluation (criticism) tools, is proposed based on the methodologies adopted by bridge design experts. The development of a KBS for the conceptual design of concrete road bridges is then described including the knowledge involved, its organization and representation schemes. Working of the KBS is explained through an application example. The main thrust of this-paper is on the critical evaluation of various generated feasible solutions.