The question of whether travel demand estimates can be improved through the subdivision of certain traffic analysis zones for the future year projection period is investigated. Because traffic analysis zone systems were likely developed in the 1960s for most regional studies, the larger and less populated zones have probably experienced significant growth over the past 20 to 30 years. Criteria are needed to determine which traffic analysis zones should be subdivided in the process of forecasting future travel and to test whether increasing the number of zones improves the resultant regional forecasts.Subarea techniques have been developed and applied by others in attempts to develop more accurate traffic data for project-specific needs. The subarea approach suffices for project needs, but the adjustments and modifications are not usually fed back into the regional modeling process. Therefore, the time and effort expended in obtainingproject data are not applied to the improvement of the overall travel demand forecasts on a studywide or regional basis. Under these conditions, system planning efforts and corridor analyses do not receive the benefit of updated information or system refinements. The findings presented evaluate the improvement in travel forecasts as a result of the subdivision of zones in a regional travel demand model. Link-by-link comparisons of traffic assignments based on the original zone system and the modified zone system are made. Two major sections are provided: (a) the development of techniques to identify zones that are candidates for subdivision and (b) a test of the results of the impact on subsequent traffic assignments for the original andmodified zone systems. This paper appears in transportation research record no. 1305, Finance, planning, programming, economic analysis, and land development 1991.
Abstract