Considering highway route selection as a decision problem with multiple and conflicting objectives, a methodology is proposed in this paper to support the decision making process, which is composed of two phases: structuring the problem and analysis of alignment routes. Structuring includes identification of the decision maker, definition of a set of objectives and attributes as well as development of engineering and environmental studies. In the second phase, decision aid methods are applied to compare and sort the candidate routes according to the decision maker's preferences and estimated values for the attributes. Emphasis is given in this paper to Decision Analysis approach. The proposed methodology is applied to a case study in São Paulo, Brazil, namely the upgrading of a roadway to a motorway (Piaçagüera-Guarujá Highway). This project is analysed taking into account the following objectives: minimizing occurrence of landslides and sedimentation as well as reducing construction costs. Results indicate that this approach provides a sound and rational basis for an enlightened decision in highway route selection.
Decision making in transportation projects is not a simple task because it involves consideration on technical, environmental and economic aspects of the problem, which are frequently conflicting. The method of cost-benefit analysis traditionally used to select a route alignment does not take into account the environmental impacts associated with the project. On the other hand, the future effects of the proposed highway in the environment cannot be predicted with certainty at the time decision has to be made. The methods available for environmental impact assessment usually do not incorporate the probabilistic nature of the impacts (Bisset, 1985). The complexity of route selection, in terms of conflicting multiple objectives and the uncertainties associated with the potential impacts of the project, requires that decision be made on a rational basis.
