The role of `models' has been well accepted in the analysis of problems dealing with transportation `operations' and `planning' decisions. The paper argues that even policy issues could use a model-based focused thinking in their analyses, even though in policy issues (1) more entities are affected and have to be considered, (2) decision variables and constraints are not clearly defined, and (3) multiple objectives need to be satisfied. The paper introduces a recursive systems engineering process for policy analysis, with a significant role for models. Two case studies on policies to reduce traffic congestion are discussed. The first study relates to preferential treatment for high-occupancy vehicles for using the transportation facilities. The second study relates to altering travel demand by congestion pricing policies. Several types of models are utilised in these studies. The models provide insight, which otherwise might be difficult, on issues and sensitivities of potential decisions and assumed parameters. (Author/publisher)
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