This paper is an investigation of a new decision support approach used to evaluate potential transportation investments by using the opinions and experience of experts as its base. Modern decision-making methods such as the Cognitive Map and Analytic Hierarchy Process were used in the creation of this approach. The Cognitive Map is a process based on a chain of interviews held with transportation experts. The data obtained from the Cognitive Map were utilized to determine the fundamental and sub-criteria. Then, an Analytic Hierarchy model was established and this model was used to determine the most suitable investment choice for the Third Bosphorus crossing. The implementations of the approach and findings are summarized in this paper. (c) 2005 Elsevier B.V. All rights reserved.