Certificates of conformity have been defined in EU's Single Internal Market and Type Approval Directive (EC-92). EU's single internal market became official on 1 January 1993. Part of the "EC-92" effort was to remove the technical barriers preventing the free movement of products within the EU market. The greatest impact of this effort has been in the area of standards in the automotive sector. The EU Commission is seeking to harmonise the automotive, technical and environmental standards between all the member states. EU legislation defines the standards in the areas of noise, particle emissions and safety. In addition, the EU's Directive on Type Approval (EU Council Directive 92/53) eliminates the need for national type approval requirements by establishing one set of rules for automobiles and their components throughout the EU. This directive aims at the clarification of the type approval procedure for motor vehicles, separate technical units (i.e., trailers), and components.