The size of traffic flows varies strongly in time and space. These imbalances cause a less efficient use of available infrastructure capacity. Spatial structure can have strong impact on the direction and size of traffic flows. This paper analyses some of the effects of spatial planning on the imbalances in the use of infrastructure, especially the variety in size of traffic flows in different direction, mostly during peak hours. A theoretical analysis, supported by simple empirical tests, led to the conclusion that separation of residences and employment is the main cause for this kind of imbalances. This conclusion is tested in a case study. For the `Oostflank', a part of the Dutch `Randstad', are scenarios composed for the spatial development in the 2010-2030 period. The main variable in the scenarios was the degree of mixing of residences and employment in the various zones of the Oostflank. With the TransCAD model a simple calculation is made of the transportation demand in the composed scenarios. Differences in degree of mixing has major effects. A better mix of residences, employment and services causes a more balanced distribution of traffic flows over the networks. A more equal distribution of workplaces and houses causes a smaller amount of infrastructure needed. (A)
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