Aggregate Travel Demand Analysis With Disaggregate or Aggregate Travel Demand Models
Transportation Research Forum Proceedings, pp. 583-604, August 1973, R.B. Cross Co., Oxford, Indiana.
Antti Talvitie (aptalvitie(at)gmail.com)
ABSTRACT
THE PURPOSE OF THIS PAPER is to develop a method of aggregation to be used in travel-demand analysis and forecasting. This is an important task because aggregation is always needed in travel demand anal sis. Transportation systems and people need to be aggregated geographically into zones to facilitate demand forecasting aggregation of heterogenous modes of travel is often done to simplify the analysis process; heterogenous people are lumped together for fewer market segments to reduce the size of the problem and so forth.
Explicit treatment of the aggregation problem has been ignored thus far in travel demand analysis and forecasting. Aggregation has been regarded as an evil, a source of error, which it is and a thing to be avoided rather than utilized. It has also been customary to put the blame on models; for example, aggregate travel demand models are accused of losing information that was never given to them; or that disaggregate models may not be used with confidence in aggregate travel forecasting because they pertain to an individual and so forth.
In subsequent sections a systematic method is developed to accomplish aggregation, especially geographic aggregation, in travel demand analysis and forecasting. After an initial discussion of the aggregation problems in different types of travel demand models, the problem of using disaggregate or aggregate travel demand models in forecasting travel is discussed and analyzed. This analysis establishes the fact that the average zonal value in travel forecasting independent of whether disaggregate or aggregate travel demand model is used. The practical problem of obtaining these values is discussed before concluding the paper.
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