ABSTRACT
In Part IV we examine several case studies of the effect of transportation infrastructure investment on urban and regional development.1 A major conclusion from these studies is that such developments are difficult to measure and to substantiate. The main reasons for this are the scale of the analysis, unaccounted for spillover effects and the presence of many other intervening variables, mainly counterproductive local policies. But what about macro level (national or state) analysis where these effects are either inconsequential or can be controlled for, as can the effects of other key aggregate variables? In this chapter we examine this issue with regard to two key questions. First, does the level of the infrastructure stock (primarily transportation infrastructure) affect national or state economy growth? Second, if it does what is the marginal contribution, from additional investment in public capital, on factor productivity?
