Abstract
This study suggests some ways of viewing the integrated models through four aspects: needs, model structure, mathematical functional form, and level of aggregation. It describes the importance of understanding the properties of mathematical functional form in models, and the functional properties can be significant criteria in judging similarity between the model and real phenomena. The study also discusses the level of aggregation in space, time, stocks, and behavior of decision makers with linkage to accuracy in representing real phenomena. It emphasizes the fact that high levels of complexity and detail in model structure and composition of components do not always guarantee better replication and forecasting of real phenomena in transportation and land-use systems. The more important factor is choosing the right model for the purpose of policy analysis.