Sequential Demand Analysis

As stated earlier, even though the assumption of the existence of a strict sequence in the decision making process of a potential trip maker may be debatable, generally sequential demand analysis is used to determine the travel demand. As will be seen throughout this section, even with this simplifying assumption of sequential decision making, the analysis of transportation demand remains sufficiently complex.

Figure  shows a schematic of the sequential demand analysis procedure. The figure attempts to not only illustrate the logic of the analysis procedure but also gives the names of the different classes of models used to mathematically describe each decision making phase of the analysis procedure. Each of these classes of models are described in detail in the next four subsections.

Before presenting the models a general overview of the entire process is provided. In this analysis procedure, first the entire study area is divided into various zones. These zones are generally obtained from the land use pattern of the area. Next for each zone the total number of trips generated in that zone are estimated using the trip generation models. The output of the trip generation models are then used to determine the number of trips between all zone pairs using the trip distribution models. Given the trip distribution pattern (which is often referred to as the origin-destination (O-D) matrix) the relative share of these trips for the different modes are estimated using the mode choice models. Finally, the traffic assignment models estimate the volume on each link of the network by determining the routes that will be used by the trips.

図: Sequential demand analysis procedure.