Barbara Gruehl Kipke

Bicycle Usage in Two Cities of Africa

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INTRODUCTION - Basic Considerations about a Behaviour-Oriented Model

Based on the behaviour-oriented model ORIENT (32), that only considers the workday passenger traffic, an extension to include all traffic throughout the week will be made. This "situational approach" (5) will be used in a modified form for transportation prognoses based on individual behaviour patterns and similar travel behaviour groups. It includes passenger traffic within the city limits of the chosen cities, divided into traffic cells. Starting point of the daily activities is home base (Fig. 3).

Figure 3
SPARMANN's ORIENT

Contrary to the traditional 4-Step-Model (trip generation, trip distribution, modal choice, traffic assignment), individual trips are always the basic unit.

The groups are formed so that the type of trips within a group are as similar as possible, whereas different groups are as different as possible. The separation of the population into similar travel behaviour groups is therefore not based on the number of trips, but rather mainly depends on the major trip purpose and transport modes chosen. At the same time, tempora1 and spacial distinctions between groups are established. In the case of developing countries, it means that a substantially different classification is required than is the case for industrialized countries. In developing countries travel behaviour is mainly dependant on access to transport modes within households and status within the household (Fig. 4).

Figure 4

Individuals with similar activity chains are combined into similar travel behaviour groups. Activity chains are a succession of activities by one person, that causes a succession of trips to occur with a certain probability within a behaviourly homogeneous group. In consideration of the situation in developing countries, the original five activities (Fig. 5) were supplemented to include the transport of loads (e.g. transportation of water).

Figure 5

When choosing transport modes, all possible inner-city means of transport have to be considered, because the simulation takes place within a closed system. This is in agreement with the many authors who state that mobility should not be reduced to motorized mobility. In view of the situation at hand, the following transport modes will be distinguished:

1. walking
2. public transport
3. bicycle
4. moped, motorcycle
5. private motor vehicle
6. passenger (of 3, 4, 5)

Starting point is the present supply and demand situation in the transport sector, that is based on the activities of individuals (Fig. 6 ). The transport supply situation should not be treated as a given, because it is possible to influence it by means of transportation planning measures (Fig. 7). Furthermore, an understanding is necessary of mode distribution, based on the process of decision-making at the household level. A well-founded understanding of the transport demand situation, that is to be gained with the help of a behaviour-oriented model based on household surveys, can allow changes in the transport supply via transportation planning. Urban planning has implications on city structure and thereby influences the demand for transport. The more decentralized the structure of a city, the less traffic volume is incurred.

Figure 6
Concept-Context Pattern

Quelle: Heidemann, C.

Figure 7

In order to compare various possible developments, bicycle traffic planning scenarios are to be developed.