سرمایه گذاری حمل و نقل و توسعه اقتصادی

This paper describes the development of approaches to analysing the links between investment in transit and economic development. It indicates the need to bring together disparate approaches from urban economics and transportation economics to get a full understanding and uses recent results on agglomeration economies to present a more rigorous model of the wider economic benefits of transit investment. Although the evidence increasingly points towards identifiable benefits over and above those captured in conventional transport cost-benefit analysis, the chapter counsels against the assumption of simple rules.

The role of transport in the urban economy has been the subject of much controversy. In this paper we attempt to sort out a coherent story of the role which transit investment can play drawing on both the classic analyses of this subject and more recent research. Whilst there is no denying that improved transportation will make the wider urban economy function more efficiently, there have been significantly different views on the extent to which there are any wider benefits which cannot be captured simply by those benefits accruing directly to users. Thus one argument would be that, whilst transit investment may have significant impacts on urban form and growth, any investment appraisal exercise can safely ignore these wider effects. On the other hand it is argued that the existence of increasing returns to scale in the activities which use transport will lead to agglomeration effects which are not so captured and hence there is a need to measure wider economic benefits separately. The secondary question is whether such effects are consistent between different urban areas and types of investment, such that a simple multiplier or add-on can account for these wider economic benefits, or that all such effects are case specific.

Perhaps the key implication of this discussion is that simple rules on the wider benefits of transit improvement for the local, regional or national economy can be dangerous. Investment in transit could seriously damage the health of the local economy, but by the same token, failure to invest in transport could also damage it. There is no universal rule, such that calculations as reported in Table 1 have to be based on the specific evidence for that city. As we have also seen from the property value studies there are substantial variations in revealed results and these can often be city-specific. The greatest danger is that we transport evidence on agglomeration economies from one city to another and apply them without due regard to the industrial structure or market structures of that city.