by Michael Wegener
The previous chapters in this Handbook have shown that spatial development, or land use, determines the need for spatial interaction, or transport, but that transport, by the accessibility it provides, also determines spatial development. However, it is difficult to empirically isolate impacts of land use on transport and vice versa because of the multitude of concurrent changes of other factors. This poses a problem if the likely impacts of integrated land-use and transport policies to reduce the demand for travel are to be predicted.
There are principally three methods to predict those impacts. The first is to ask people how they would change their location and mobility behaviour if certain factors, such as land use regulations or transport costs, would change ('stated preference'). The second consists of drawing conclusions from observed decision behaviour of people under different conditions on how they would be likely to behave if these factors would change ('revealed preference'). The third method is to simulate human decision behaviour in mathematical models.
All three methods have their advantages and disadvantages. Surveys can reveal also subjective factors of location and mobility decisions, however, their respondents can only make conjectures about how they would behave in still unknown situations, and the validity of such conjectures is uncertain. Empirical studies based on observation of behaviour produce detailed and reliable results; these, however, are valid only for existing situations and are therefore not suited for the assessment of novel yet untested policies. In addition it is usually not possible to associate the observed changes of behaviour unequivocally with specific causes, because in reality several determining factors change at the same time.
There are principally three methods to predict those impacts. The first is to ask people how they would change their location and mobility behaviour if certain factors, such as land use regulations or transport costs, would change ('stated preference'). The second consists of drawing conclusions from observed decision behaviour of people under different conditions on how they would be likely to behave if these factors would change ('revealed preference'). The third method is to simulate human decision behaviour in mathematical models.
All three methods have their advantages and disadvantages. Surveys can reveal also subjective factors of location and mobility decisions, however, their respondents can only make conjectures about how they would behave in still unknown situations, and the validity of such conjectures is uncertain. Empirical studies based on observation of behaviour produce detailed and reliable results; these, however, are valid only for existing situations and are therefore not suited for the assessment of novel yet untested policies. In addition it is usually not possible to associate the observed changes of behaviour unequivocally with specific causes, because in reality several determining factors change at the same time.
Mathematical models of human behaviour are also based on empirical surveys or observations. The difference is that the conclusions to be drawn from the survey and observation data are quantified. Strictly speaking, the results of mathematical models are no more universally valid than those of empirical studies but are only valid for situations which are similar to those for which their parameters were estimated. Nevertheless it is possible to transfer human behaviour represented in mathematical models within certain limits to still unknown situations. In addition, mathematical models are the only method by which the effects of individual determining factors can be analysed by keeping all other factors fixed.
In this chapter recent developments in the field of operational integrated land-use transport models will be reviewed with special emphasis on their ability to test both land use and transport policies and to assess their impacts.
In this chapter recent developments in the field of operational integrated land-use transport models will be reviewed with special emphasis on their ability to test both land use and transport policies and to assess their impacts.
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