Opinion of the European Economic and Social Committee on the ‘proposal for a Directive of the European Parliament and of the Council on the approximation of the laws of the Member States relating to the measures to be taken against the emission of gaseous and particulate pollutants from compression-ignition engines for use in vehicles, and the emission of gaseous pollutants from positive-ignition engines fuelled with natural gas or liquefied petroleum gas for use in vehicles’ (COM(2003) 522 final - 2003/0205 (COD)).