The objective of this research is the development of an original methodology for the improvement of the comparability of national road accident data held inside CARE, the European database with disaggregate road accident data. The originality of this methodology lies to the fact that comparability is achieved through restructuring of existing national road accident data files without any harmonisation of the original data collection methods of the EU member states.  The methodology developed consists of three distinct phases concerning the selection of priority variables and values, the elaboration of common definitions and labels and the development of the related transformation rules at a very detailed level.  The application of this methodology has produced a list of common-definition values of 48 priority variables, making thus CARE database a more useful tool for European-level comparisons.