Reversing Direction of Transportation Planning Process

Abstract

The process of transportation planning begins with an assumed land use and then projects future traffic volumes. To determine land-use limitations as a function of the capacity of the transportation system, we reversed the direction of the planning process, beginning with transportation system characteristics as the independent variable and employment and population as dependent variables. We ultimately developed a direct estimation model. This technique directly estimates zonal trip ends based on transportation system variables that include link volumes, roadway types, travel distances, and the geographical position of the zone. Additionally, we regressed retail employment, nonretail employment, and population to zonal trip ends. We calibrated this model for the 1967 base year in the Charlottesville, Va. area and then applied it for the 1979 forecast year. We then used lessons learned to calibrate the model for the 1979 base year (a training set of data) and apply it for the 1990 forecast year (a test set of data). We suggest how this model formulation might be interpreted to yield land-use limits as a function of traffic volumes and discuss subsequent application of this approach to consider policy options that arise in the context of transportation planning.