Results from past studies on transport demand elas- ticities show a large variance. This paper assesses key factors that influence the sensitivity of public transport users to transport costs in Europe, by car- rying out a comparative analysis of the different elasticity values of demand for transport that are being used in some of the different Member States. Our empirical base is elasticity studies in Norway, Finland, the Netherlands and the United Kingdom. The paper identifies a set of potential factors caus- ing variances between results of different studies. An indepth rough set analysis of causes of variances between elasticity values across the four countries is presented. Our analysis supports the literature, which indicates that the difference between aggre- gated, empirical-based research methods and the use of disaggregated choice models, as well as model assumptions, explain the variance in elastici- ty values across studies. It also appears that the country involved, the number of competitive modes, and type of data collected are important fac- tors in accounting for the size of elasticities.