The aim of this thesis is to provide to the governmental decision-maker/user, an instrument that can assist him/her in improving the infrastructure investment decision in the economical, environmental and sustainable aspects. This means that, the Return on Investment (ROI) of the concerned transport infrastructure, satisfying environmental and sustainable constraints must be positive, and corresponding to an optimal investment cost. The decision support system can be applied in two dimensions. One dimension is where the real negotiation process is occurring between private and public stakeholders, called “real time negotiation process”. The second dimension is where the negotiation process is impelled by the user (public part) without private stakeholders interaction (but with interaction through simulation), called “virtual negotiation process”. The simulation and local optimization techniques, in phase with agent technology, used in the “virtual negotiation process” enable us to achieve a certain amount of alternative decisions to the primary/suggested decision to be evaluated. The CommonKADS methodology with mathematical modeling, and agent technology have been the support respectively for extracting and implementing the knowledge in the domain, monitoring, automating and updating the decision process. The principle of “Joint logistic” [1] in my effort concerns by the means of sharing financial and information resources; This leads to the empowerment of the supply chain feedbacks (roles), involved in the earlier stages of public transport decision making-process. It appears that within the decision-making process, the government is often dealing with the conflicting objectives, while interacting with the business stakeholders. For instance, the estimated investment cost of a specific transport infrastructure can exceed the income generated by this infrastructure, thus the ROI of the concerned transport infrastructure (TI) will be negative. From this perspective the government faces three choices: a) increase the rate of the taxes applied on that transport infrastructure or any other taxes, in order to make ROI positive, this can be matter of discussion/disagreement for the business community b) reduce the investment cost which means suggest a different TI with a lower quality standard compared to the previous; this can also be a matter of disagreement between the two concerned stakeholders. c) delay of the investment in the specific transport infrastructure. In fact in the most situations the government uses the first approach, which effects might be consequently unpredictable and disastrous in the economical and environmental sense for the government. From this point of view my attempt is to propose an intelligent decision support system for governments or project groups (e.g. East West project group), involving conceptually as components web portal, database, simulator and knowledge base, that bases on an approach, that enables this negotiation/information exchange at the earlier steps of decision-making situation. This is concretized by gathering in real time accurate and relevant information from the private sector; furthermore the knowledgebase of the designed system is conceived via the experience and historical knowledge of the concerned experts in the domain.