A core issue is to understand why traffic forecasts are wrong, and how they can become significantly more accurate. To understand this, forecasted versus actual traffic are studied: How do traffic volumes after project opening compare to the forecasts? Is there any systematic pattern in deviations between forecasted and actual traffic volumes? Also models behind rejected projects will be analysed, since they may be more precise and/or have less ignorance bias. The empirical analysis will subsequently be used to discuss the inherent assumptions of the traffic models.
We intend to gather information about the highest possible number of the road and rail investment projects carried out in Denmark, Norway and possibly Sweden during the period 1980 - 2007. Besides looking for statistical relationships relevant to the elucidation of the research question, we will make three or four of the investment projects subject to more thorough case studies.
An interesting question to be answered from the quantitative survey is whether there is empirical justification to conclude that uncertainties and risks in the basis for decisions are lower in Public Private Projects, than in traditional public procurement?