(20)Since the objective of this Directive, namely the improvement of the EU-wide standard of initial qualification and periodic training for drivers of certain road vehicles for the carriage of goods or passengers, cannot be sufficiently achieved by the Member States but can rather, by reason of the cross-border nature of road transport and of the issues this Directive is intended to address, be better achieved at Union level, the Union may adopt measures, in accordance with the principle of subsidiarity as set out in Article 5 of the Treaty on European Union. In accordance with the principle of proportionality, as set out in that Article, this Directive does not go beyond what is necessary in order to achieve that objective.