We are doing a study on what explains differences in BCRs between transport projects. Are there differences in BCRs between regions, projects types, modes etc.? Are there any other explanatory factors that can explain differences? We do analyses on a data set of more than 1000 projects, so we are confident that the results will be interesting, but we need to review some relevant literature to frame the study. I've found one by Nicolás González-Pampillón and Henry G. Overman from 2020, and a couple more from the 'grey' literature, but there seems to be very few studies on this topic. Does anyone know any relevant studies?