The market system is unavailable to reflect negative externalities, caused by road motor trafic, in the realized prices. For that purpose, it would be appropriate to implement a general environmental road tax in the European Union member states. The question is whether the national registers of vehicles are prepared for such a change. Whether this is the case at present, may be found out by means of analyses of the available national registers. The next step is synthetic: the data must be subsequently completed on the basis of the knowledge of needs of currently existing systems of road motor vehicles taxation. In the end, the identified results may be supplemented with the known data published by international institutions. The results of the research show that the present systems of road motor vehicles taxation are utterly different and distortive. Only 12 countries of the European Union have registers which were clearly identified as prepared for the application of the environmental tax. Registers of the remaining countries do not contain one or more data that are necessary for the implementation of the environmental tax. For this reason we may assume that regardless of other determinants, environmental road tax shall not be introduced throughout the European Union in the foreseeable future.O