GIS AND TRANSPORTATION-PLANNING - A CASE-STUDY

It was hypothesized that a GIS model would refine the process of transportation planning by yielding improved interim and final results which reflect greater consistency in the consideration of planning factors and that these improvements could be quantified by comparing differences between the GIS and non-GIS models. Application of the GIS and non-GIS methods to an identical dataset provided the basis for an evaluation of the differences between the GIS and non-GIS model computations and an analysis of how the differences in the two models alter travel demand estimation.It was shown that the GIS model produced a larger estimate of the total developable vacant land through consistent elimination of environmental and geographic constraints. The GIS model also produced smaller estimates of the individual growth areas and helped to identify weaknesses in the manual overlay process. The results of the macro and micro level travel demand analysis indicate that the improved land-use estimates resulted in minor improvements to the travel demand estimation. It was also shown that the differences in traffic volume estimates produced by the two models were not great enough to potentially cause over- or under-designed facilities and that system level factors, such as average trip length and traffic volumes, do not differ greatly between models. The results also identified serious differences in the amount of developable vacant land available for accomondating future growth. It was speculated that these differences were the result of human errors and inconsistent consideration of environmental and geographic constraints. Using study results, three primary factors that small towns should carefully appraise when considering the use of GIS strictly for transportation planning purposes were identified.