Travel demand arises when a series of activities (home - work - shopping - home) cannot be carried out at the same location and therefore a change of location is necessary (Fundamentals: Transport demand model).
The number of these changes of locations, i.e. the number of trips between zones or main zones, is coded in demand matrices. These are calculated on the basis of socio-demographic data and can be compared with transport surveys.
The temporal distribution of trip requests within each time interval of an observed time period is described by a start time and a demand distribution curve (time series), which is considered in public transport assignments and in dynamic private transport assignments. The time series is ignored in the case of static PrT assignments.
Demand models are used to compute the number of trips. These demand models include various demand objects:
- Activities, from which activity pairs and activity chains can be formed
- Person groups, in which the population is distinguished by traffic behavior
- Demand strata, connecting activity chains and person groups
- Structural properties, describing the potential of zones as origin or destination of a trip (only for demand models of the types EVA-P and tour-based model)
- Demand strata which connect source sectors and delivery concepts (only for demand models of the tour-based freight type)
Based on these demand models and on skim matrices, the three classic steps of traffic modeling (trip generation, trip distribution and mode choice) are calculated (Fundamentals: Demand model).
All demand data (matrices, time series, allocated demand segments and demand model data) constitute the demand description and are saved to demand data files *.dmd.
For activity-based models, the objects persons, households, schedules, tours, trips, activity executions, and activity locations can be managed for the mapping of synthetic populations and their activities distributed in space (Managing objects of activity-based models).
