This study supplements extant literature on implementation in the European Union (EU). The quantitative analysis, which covers the EU transport acquis, reveals five main findings. First, the EU has a transposition deficit in this area, with almost 70% of all national legal instruments causing problems. Second, transposition delay is multifaceted. The results provide strong support for the assertion that distinguishing between the outcomes of the transposition process ( on time, short delay or long delay) is a useful method of investigation. Third, factors specific to European directives ( level of discretion and transposition deadline) and domestic-level factors ( national transposition package and number of veto players) have different effects on the length of delay. Furthermore, the timing of general elections in member states as well as policy ( sub) sector-related accidents influence the timeliness of national transposition processes.