Does transition mean complication? Sixty years of regulatory complexity in EU transport

The problem of regulatory complexity has received significant attention among policy design and policy growth scholars. However, measuring regulatory complexity and formulating effective policy responses to deal with regulatory complexity remains an unresolved challenge. To address this gap, we develop an index of regulatory complexity and apply it to a full set of EU transport legal acts between 1960 and 2026. We further undertake a document analysis to trace the EU Common Transport Policy’s historical development and identify specific policy paradigms that drive or moderate regulatory complexity. Our analysis shows that as the EU Common Transport Policy paradigms change, so does regulatory complexity. We find that after the EU mobility policy entered a phase of sustainability transition in late 2000s, regulatory complexity increased significantly. Where the EU Common Transport Policy paradigm of sustainability transition played a less prominent role, regulatory complexity was lower. We further find no unambiguous correlation between the regulatory regime’s complexity and its size, that is, the number of transport legal acts. These findings advance the understanding of regulatory complexity by suggesting that sustainability transitions can drive complexity, and for good reasons. Our contribution invites a new way of thinking about how to respond to regulatory complexity. We propose that if sustainability is sacrificed in the process, blanket deregulation might not always be the preferred option to mitigate complexity. Instead, we call for empirically informed and environmentally responsible policy responses to regulatory complexity. This work invites further investigation into policy complexity by developing a more accurate measure of policy output and complexity and applying this measure to studying policy complexity in more diverse empirical settings such as EU energy policies or the national sectoral policies of Member States.