The application of meta-analysis to enhance the appraisal of transport projects

There is an increased interest in applying meta-analysis techniques in transport studies to understand different concepts used in transport project appraisal. Meta-analysis helps to examine the variation of these concepts to obtain better understanding. Moreover, the thesis considers the implications of applying meta-analyses in transport economic studies, particularly its role in informing policy decisions to enhance the appraisal of transport projects.
Meta-analysis is applied to better understand the factors of variation of estimated metrics and outcomes in project appraisal. This allows for a deeper understanding of the concepts, through explaining the main factors leading to the variation, which allows for enhanced appraisal processes in transport projects. Three meta-analysis applications were conducted for different concepts related to project appraisal. The first and second applications concerned the value of travel time savings (VTTS) metric, which is a key input for the appraisal and evaluation of transport projects. The former application focused on understanding the VTTS metric in freight transport, while the latter application focused on income elasticity of the VTTS in passenger transport as a main metric used in project appraisal. The third application concentrated on the variation of appraisal outcome to enhance project appraisal by understanding cost overrun and benefit shortfall concepts.
The thesis applied different techniques derived from reviewing medical applications to obtain more reliable conclusions. These applications show statistically significant variation of different factor types, such as structural, methodological, behavioural, and socioeconomical. Furthermore, these applications provide implied values that help in predicting costs and benefits of future projects and transferring standard values to other contexts.
Overall, this thesis highlights that the meta-analysis can help in providing insight into the reasons for variation between the results of previous research studies, and how the insight derived can have direct implication for recommending transferable values of key transport attributes. As well as providing evidence that Highways England has gotten better in forecasting the cost of schemes. The thesis suggests some techniques for the future improvement of meta-analysis generally, and for the application of meta- analysis to the three concepts of interest specifically.