Urban trips have a wide variety of purposes. The above figure illustrates a typical set of daily trips associated with one individual; his/her activity space (daily spatial behavior). Although the individual is directly involved in passenger movements (in this case as the driver), freight trips are also derived from all these daily activities.
- Passengers trips. The first trip is concerned about commuting to the place of work. It is combined with dropping off a child at school and then driving to work. At lunchtime, a walking trip to a nearby restaurant is generated. Then, a drive back home and a trip to a shopping mall in the evening where consumption (grocery) and leisure activities are taking place.
- Freight trips. Many freight trips can be derived from daily home-based and work-based activities. The great majority of these trips are not associated with the activities of a single individual, but usually reflect the aggregate demand of many. For instance, garbage can be picked up from residences, and parcels can be dropped and picked from an office building, both of which occurring along a route. The function of consumption also generates substantial freight flows. For instance, restaurants and shopping malls have to be resupplied, often on a daily basis. The growth of e-commerce has resulted in more home deliveries of parcels.