ABSTRACT
This chapter discusses the use of costbenefit analyses of transportation infrastructure investment projects. It considers the quantitative estimates of costs and benefits to be inevitably inaccurate for ontological reasons, despite the purported higher exactness of costbenefit analysis than other evaluation methods. The chapter argues that costbenefit analysis as practiced in the transportation sector is based on a number of untenable ontological and epistemological assumptions. According to Ackerman and Heinzerling the method of costbenefit analysis generally promotes a deregulatory agenda under the cover of scientific objectivity. Studies indicate that biased forcasts have several explanations of forecasting errors: ontological explanations, optimism bias, technical problems, but also 'strategic misrepresentation'. In principle, similar bias will also occur in relation to other long-term environmental consequences, such as loss of biodiversity and biological productivity due to local pollution, and the fragmentation of natural areas represented by transportation infrastructure construction.
