In this chapter we perform a number of tests of the proposition that PPPs provide superior cost and time outcomes than Traditional projects. These tests are based on publicly available data for a 54-project dataset that has been described in earlier chapters and is detailed in Appendices B and C.
The approach in this chapter can be described as follows:
• A statistical analysis of time and cost over-runs under PPPs and Traditional procurement; and
• A graphical representation of the data to show the spread of outcomes.
As a generalisation, it can be said that:
• Traditional projects were the subject of significant optimism bias, while at the contracting stage PPP projects were not subject to optimism bias.