In order to assess the optimism bias levels for current and future projects, it is necessary to review past projects and take onboard any possible lessons learned.
To achieve the objectives of the study, the optimism bias at business case (as well as at contract award) with respect to works duration, project duration, capital expenditure, operating expenditure, unitary payments and benefits shortfall had to be measured. In addition, the project risk areas giving rise to optimism bias had to be identified along with the contributions and impacts of each project risk area to the measured optimism bias.