Traffic simulation packages like CORSIM and VISSIM are frequently used as tools for the analysis of traffic since they are effective approaches for quantification of the benefits and limitations of different alternatives. The concern of those who are cautious or skeptical about the application of a complex program to making a critical design decision is often appropriate, as many models are unproven or little information about their accuracy is available. As these simulation models become easier to use, it may be practical to use more than one model in some studies. The two-model approach was applied as a means of making the analysis more reliable and the results more defensible. The results proved the consistency and reasonableness of the simulation tools and provided everyone involved with confidence about the analysis. The study also illustrated the value of using a range of performance measures and a sensitivity analysis. More generally, it proved the value of providing as much comparative information as possible before making a design decision. The results were generally consistent, and the end product was a set of clear, defensible, and well-supported conclusions. Although the experience gained through the application of CORSIM and VISSIM was in some ways unique to the study area, this experience can provide insight to other transportation professionals charged with selecting and applying these simulation models to similar networks. To that end, some of the characteristics of both models are contrasted.
