Our sample consists of projects from the Investment Monitor that:
• are road or rail projects;
• had an initial expected cost of at least $20 million in nominal terms; and
• are 'public' projects.
We define a 'public' project as an investment by a government body in publicly accessible road or rail infrastructure. Our definition includes Public Private Partnerships (PPPs), but excludes investments by private operators of public infrastructure. The Investment Monitor has a variable indicating whether projects are public, private, or a PPP, but we do not rely on this variable because it is incomplete and is not consistent with our preferred definition in some cases.
For our analysis of cost overruns, we considered only projects that had been recorded as 'Completed' in the Investment Monitor's historical database as at the end of March 2020. The historical database is a record of, among other things, the final cost and status of each project that leaves the Investment Monitor's quarterly 'pipeline'.
For Figure 1.1 on page 5, Figure 1.2 on page 6, and Figure 4.1 on page 22, we considered only projects that had been recorded as 'Completed' or were still in the pipeline as at the end of March 2020. This removed some irregularities in the data relating to projects that do not appear to have been seen through to completion.