This paper uses the framework proposed by Rouwette et al. (2002) to describe the group model building stage of a project to integrate land use, transportation and air quality planning in a rapidly growing metropolitan area. The purpose of the paper is twofold: to present a case of group model building in the public sector, and to test the framework for reporting about group model building interventions. The main goal of the intervention described is to evaluate the effect of potential land use and transportation policy changes on urban quality of life factors such as air quality and traffic congestion. A secondary goal is to foster interagency and intergovernmental collaboration. After approximately 15 months, the project is at the end of its first stage. A quantitative model has been completed and is being tested by the modeling group. In the next stage, the model will be used by policy-makers for policy evaluation.