Transportation modeling in a changing world: a Miami case study

Cities throughout the United States are placing increasing demands on the Urban Mass Transportation Administration for funding of improved transit systems. Approximately 40 of these communities are serious about developing rapid transit in one form or another. However, as a class, these proposals are extremely expensive and could utilize the entire Urban Mass Transportation Administration funding as established under the National Mass Transportation Administration Act of 1974 ($11 billion over six years). To assure fair, systematic evaluation of these requests, the Urban Mass Transportation Administration has developed a series of policy guidelines that emphasize local decision-makers in creating a sound approach to alternative systems evaluation so that the technical results of all "lead-in" studies to rapid transit funding requests can be factually supported. Traditional technical approaches to transportation models are not tailored to the needs of planners and decision-makers. Using the Miami setting as a basis, a modeling approach is discussed that is directed toward: * Providing local officials and planners with policy options that will allow them to achieve stated goals with regard to the role of the transportation system in the urban environment; and * Evaluating quantitatively and analytically the effects of various uncertainties on the capital-intensive system investments. This approach uses a mathematically based risk analysis model together with sensitivity analysis and policy model split techniques. The first model evaluates the degree of uncertainty involved in patronage and revenue projections and thus provides measures of the risk involved in investment alternatives. The latter set of models is capable of developing system characteristics and policy combinations that will achieve modal split objectives for the region and for certain predefined trip and tripmaker strata. In addition to discussing these approaches and their application in Dade County, Miami the role of calibration in the behavioral modeling package is described and illustrated.