With her chair in urban development management, Ellen van Bueren investigates policy, governance and management issues. Cities, as economic and cultural centres in our society, are major consumers of resources. They not only contribute to problems such as climate change, but also experience the risks and consequences thereof. Technological solutions to these problems are difficult to implement. They require larger-scale system changes, or encounter resistance. Making cities sustainable not only requires technical solutions, but also institutional innovation. A socio-technical-ecological system approach to cities shows the coherence and complexity of issues. Issues play on multiple scales, are cross-sectoral, and require an interaction of citizens, companies, and governments. Moreover, the playing field between these groups of actors is changing rapidly, technological empowerment in particular has made the citizen a much more equal player alongside the government and business. Existing instruments and approaches are not sufficient to approach sustainability issues. To identify and address these issues, cooperation between science and society is necessary. Multi- and transdisciplinary learning environments enable researchers and students to identify issues, to answer questions and to try out solutions together with stakeholders. Such environments are indispensable for the development of sustainable cities.

Societal and technological developments (such as the digital and energy revolutions) move faster than existing institutions can keep up with. The developments may lead to a metaphorical institutional void, which brings questions about the nature of the void, the changing rules, practices and responsibilities, and about the strategies to deal with the void. The concept has been around for a while but (again) seems relevant to understand current socio-technological innovations and challenges, that also allow us to further conceptualise the institutional void. In this introduction to the issue, we discuss the concept of an institutional void and explore how it is used in various domains of study, including public administration. We argue for how the concept is relevant today and therein also introduce the topics that are discussed in this special issue.

This special issue contains five articles based on empirical research into energy transition at the local level. The focus is on the role of local authorities in the energy transition and on partnerships between local authorities (municipalities, provinces, regions) and local communities in the area of sustainable development. The three guest editors have also written an introduction and conclusion for this special issue.

In polycentric urban regions one can find different, mutually related cities without a clear centre. In these regions cities cooperate to attract inhabitants and employment, but at the same time they are each other’s competitors. The Randstad (Netherlands) and the Rhine-Ruhr area (Germany) both can be seen as polycentric regions. The authors explore to what extent these regions possess a common identity and common agenda and to what extent this promotes the sustainability and energy transition of these regions. In both regions identity appears to have grown especially at subregional level, by historically developed spatial-economic profiles of the different cities or suburban regions. In addition the cities in these regions more and more wish to distinguish themselves in the area of sustainability. Every city wants to be the smartest, greenest and healthiest, and to be at the forefront in energy transition and climate mitigation. In the Dutch Randstad this competitive drive especially seems to contribute to the realization of sustainability projects at the local level. And that is exactly why regional cooperation is important: to allocate resources as well as possible and to avoid transfer to others. This can be improved by the development of subregional or regional sustainability visions.

In this closing article we summarize the results of the individual articles of this themed issue and draw common lessons. With regard to cities as living labs, we conclude that three challenges need more attention: (1) unclear or contradictory goals and expectations, (2) organizational confusion, and (3) the lack of institutional links. Based on these, we offer a number of recommendations for research and practice in public administration.

The city is hot: solutions to the world’s everyday problems are increasingly sought at the local level. Local administrations are handed more responsibilities through decentralizations and much is expected of the pragmatic skills of mayors. A great deal of hope is directed at the self-organizing abilities of cities, which can be seen as laboratories for social change and improvement. In this themed issue we will critically review these high expectations of cities and the local level. Can cities live up to these expectations, and at what point does ‘hope’ become ‘hype’? This introductory article mainly focuses on the concept of living labs, which are presented as an accessible, innovative and pragmatic way to address social issues in neighbourhoods.

Why is there an on-going debate about climate change? We analyse this question from a framing point of view. We analyse four well-known frames in the climate change debate, and see what kind of reactions and reframing they invoke. The analysis shows that simple frames with an inherent logic, which activates underlying values and which are easy to communicate strongly resonate. It is difficult to counter such a frame. Opponents of the frame are often seduced to counter the frame by using the same wording. In this way, they step into the frame of their opponents and thus confirm the frame. To conclude, the article discusses two possible strategies for reframing: to couple the frame with other frames, and to suggest an alternative frame without stepping into the opposed frame.