Abstract Better regulation cannot be achieved without serious attention to transposition. The quality of EU regulation is crucial to ensuring that Community law is promptly transposed into national law within the prescribed deadlines. But good quality transposition (clear, simple, and effective) goes beyond pre-legislative consultation processes and more frequent use of impact assessments as agreed in the 2003 Interinstitutional Agreement on Better Lawmaking. Presenting new data that covers the full population of all EU transport directives from 1995 to 2004-including the national implementing instruments of France, Germany, Greece, Italy, Ireland, Spain, Sweden, the Netherlands and the UK-this study shows that elements of the EU directives delay transposition. The binding time limit for transposition, the EU directive's level of discretion, its level of detail, its nature and further characteristics of the directive's policy-making process are all factors. These determining factors are crucial to explaining why Member States miss deadlines when transposing EU Internal Market directives. Brussels' efforts to simplify and improve the regulatory environment have to go beyond more preventive action to strengthen the enforcement of EU legislation at the member-state level if they want to address the Internal Market constraining effects of Member States' non-compliance. This study argues that far-reaching decisions made in the European Commission's drafting and EU policy-making phase have the greatest effect on the European regulatory framework in which businesses operate and the free movement of goods, persons, services, and capital is at stake. Implementation should be part of the design.