AbstractPolicy mixes—strategic combinations of policy objectives and instruments—are crucial for addressing complex societal challenges in sustainability transitions. Yet, how their characteristics—such as consistency, coherence, and credibility—emerge, and who shapes them remains unclear. This study poses the question: what role do actors play in shaping the characteristics of policy mixes? By integrating a co-evolutionary framework of policy mixes with a typology of policy entrepreneurship, we trace cycling policies in two Dutch cities using documents, reports, news articles, and interviews. Findings show that political entrepreneurs strengthened political credibility, problem brokers aligned policy objectives with societal needs, and process brokers improved coherence between policymaking and implementation, jointly enhancing policy effectiveness. We formulate propositions that clarify the role of different types of policy entrepreneurship in shaping policy mixes, contributing to research on policy mixes and the role of actors in sustainability transitions.

Despite efforts to mitigate climate change, adaptation becomes critical. Among climate-induced hazards, flooding is the most costly and widespread, calling for adaptation across scales: from government-led to household-led adaptation. Private adaptation measures, if taken, reduce damages and speed up recovery. Empirical evidence suggests that among socio-behavioral factors, social norms and peer influence are crucial for households’ decisions to adapt. Yet, the role social networks play in household-level adaptation has not been studied systematically, even less so the interplay between private household adaptation and public information policies in the presence of social influences, the exchange of opinions and information within a social network that impacts individuals’ decisions. To improve the understanding of the impact of social influence on private household adaptation uptake, we build an empirically informed agent-based model of household behavior. We leverage household survey data collected in Harris County (Texas, USA) together with information on flood hazard scenarios to study the impact of private adaptation diffusion on flood damages under different social influence scenarios. Furthermore, we use the model to test how different information policy design choices—such as targeting specific households or all, and communicating different aspects of flood adaptation (e.g., flood damage, costs, or effectiveness of measures) --influence private adaptation diffusion and impact regional residual flood damage. We find that regardless of the structure of the social network, social influence triggers higher adaptation uptake by households, resulting in a 5–10% extra reduction in regional residual flood damage. Notably, the effect of social norms depends on the type of information exchanged within networks, where the opinion exchange on the effectiveness of measures and potential damages results in more private adaptation compared to the discussion on perceived costs of adaptation measures or the worry about flooding. Moreover, while information campaigns influence individual perceptions that facilitate household-led adaptation, the provision of information solely on expected damages is not as effective in steering public opinion and, thereby household adaptation, as its combination with information on coping measures that enable action. Our results demonstrate that social influence and information policy can shape the success of private action and highlight the importance of understanding the interaction among scales in climate change adaptation.

Subnational climate commitments are widely viewed as potential catalysts of national climate ambition, yet systematic evidence on whether and under what conditions subnational action shapes national target-setting remains limited. We introduce the concept of catalytic cascading to describe a cumulative process in which expanding policy commitments change the likelihood of subsequent policy commitment, even at a different jurisdictional level, through reinforcing top-down, horizontal, and bottom-up dynamics, without necessarily following an abrupt threshold or tipping behavior. We examine this theory through the lens of vertical policy diffusion, assessing whether subnational net-zero target declarations are associated with later national net-zero adoption while accounting for country characteristics and cross-national peer influences. Using a novel global time-series dataset of national and subnational net-zero targets, we estimate discrete-time adoption models using a directed country-pair (dyad–time) event history design that incorporates dyad-specific similarity and exposure measures alongside within-country subnational coverage. Across specifications, the share of a country's population, GDP, or greenhouse gas emissions covered by subnational net-zero commitments is positively and statistically significantly associated with the probability of national target adoption. The estimated relationship is gradual and monotonic rather than characterized by a sharp inflection, suggesting that bottom-up influence operates through cumulative reinforcement rather than threshold acceleration in this setting. These findings provide empirical support for catalytic cascading as an observable bottom-up linkage within polycentric climate governance and clarify the conditions under which subnational momentum is plausibly consequential for national target-setting.

Policy robustness, that is, the capacity of policies to sustain performance across diverse and uncertain futures, is increasingly considered a core objective of public policymaking. Although adaptive policymaking is widely promoted as an approach to achieving policy robustness, it suffers from a central paradox highlighted by theories of the policy process: mechanisms intended to enable ongoing adjustment can generate entrenchment and opportunistic behavior through coalition stabilization, self-reinforcing feedback, institutional friction, and strategic agenda setting. While present in all policy systems, this paradox is likely more pronounced in the Global South, where high uncertainty and constrained administrative capacity intensify the political mechanisms that undermine adaptive policymaking. Despite rapid growth in the literature on policy robustness, it remains unclear to what extent this scholarship engages with the political processes through which policy adaptation unfolds over time. This study addresses that gap through a computational review of more than 300 publications on policy robustness and adaptive policymaking. The findings show that research in this area is dominated by domain-specific applications and methodological innovation, with limited attention to political dynamics. Governance perspectives are comparatively marginal, and explicit engagement with theories of the policy process is virtually absent. As a result, policy adaptation is largely conceptualized as a design problem rather than as a contested political process. The article concludes by explaining why this omission matters for theory and practice and by identifying avenues for integrating political analysis into future research on policy robustness.

Numerous studies have found influential factors of perceived accessibility levels in recent years. What is less well understood is the effect of perceived accessibility on travel, activities, and well-being. This is a significant omission in the respective body of literature as the primary goal of the transport system is to provide users with the necessary opportunities and possibilities to reach destinations and to participate in activities. Arguably, studying perceived accessibility and its determinants is only relevant if these perceptions in turn influence aspects such as travel behaviour, activity participation, satisfaction, and well-being. To fill this gap, this paper systematically identifies and analyses outcomes of perceived accessibility in terms of travel, activity participation, and well-being. For this purpose, we first identify links with outcomes of perceived accessibility in the literature. We then offer a conceptualisation based on the relations identified in the literature, which is empirically validated using a structural equation modelling approach. We find significant relations with activity participation and travel behaviour, but also with daily travel satisfaction, residential satisfaction, and overall life satisfaction. Finally, implications for policy and science as well as a research agenda with possible avenues for future research are presented. The most important lesson is that policies that consider ‘calculated’ accessibility only may fail to enhance satisfaction with life and to reduce (transport-related) social exclusion. Still, more research is needed to understand what other impacts of perceived accessibility are and how these outcomes of perceived accessibility, in turn, reinforce levels of perceived accessibility over time.

Sustainable urban transport is a complex challenge requiring innovation in technologies, culture, and policies. However, the relatively weak conceptualisation of agency in the transitions literature limits the usefulness of this approach for the governance of urban transport. The objective of this chapter is to contribute to the conceptualisation of agency in the multilevel perspective of sustainability transitions. We propose that two types of actors exercise agency to foster innovation: technology constituencies, which promote the adoption of specific technologies by citizens, businesses, or governments, and instrument constituencies, which promote the adoption of specific policy instruments. We posit that the two constitute distinct, albeit possibly overlapping, actors and that their relationships help better understand and explain how innovations evolve. We discuss the implications of this distinction for the governance of urban transport and argue that the presence of instrument and technology constituencies, and their relationships, should be examined more closely in future research.

Innovation in public policy is a rapidly expanding field, highlighting its critical role in addressing complex societal challenges. This bibliometric review (n = 17,264) synthesizes over 50 years of scholarship, systematically identifying key gaps, including conceptual fragmentation, limited theoretical engagement, methodological conservatism, and geographic and sectoral imbalance, and underutilization of the comparative perspective. These challenges constrain the field’s ability to address pressing global issues such as climate change adaptation, digital transformation, economic inequality, and the energy transition. This study proposes a comprehensive research agenda to bridge these gaps and move the field from niches toward more inclusive, integrative, and rigorous mainstream scholarship.

Transnational municipal networks (TMNs) such as C40 or ICLEI have been posited to foster city-to-city learning in accelerating climate change mitigation and, thereby, facilitating the transition to net-zero greenhouse gas emissions. However, the existing literature on the role of climate networks has hardly examined the relationship between membership and climate change mitigation outcomes and impact, without which it is premature to be optimistic about TMNs role in the net-zero transition. In this article, we address this gap through a mixed methods analysis in the case of the C40 cities initiative. We combine a staggered difference-in-differences regression to shed light on the relationship between membership in the C40 initiative and carbon dioxide (CO₂) emissions during 2002–18 in over 700 OECD cities with a qualitative cross-case analysis of Bogotá, Colombia and Copenhagen, Denmark to unpack how and when the C40 initiative influences climate action at the city level. Results show that there is no statistically significant relationship between C40 membership and CO₂ emissions, indicating that cities in the C40 initiative may not have reduced CO₂ emissions more than other OECD cities, after controlling for socioeconomic characteristics, weather, country characteristics, city fixed effects, time fixed effects, and city-specific annual time trends. Furthermore, the complementary qualitative analysis showed the C40 network's direct intervention is limited to increasing or maintaining the ambition of cities; the network was found to have limited influence on city-level policy planning and implementation. There is a need to further study and address local policy implementation for realizing net-zero in relation to TMN membership.

Climate change impacts the power system globally. It also creates a challenge for Indonesia's energy transition, which aims for net-zero emissions by 2060. Aside from decarbonization efforts, planning for this transition adds a challenge due to the deeply uncertain nature of climate change. This refers to a condition where planners cannot agree on models, probabilities, or even which variables to prioritize. That degree of climate uncertainty has not yet been addressed in Indonesia's current power systems planning approach. Failure to address these uncertainties could bring significant vulnerabilities to Indonesia's future power system. Furthermore, only a small number of studies on power systems planning in Indonesia have addressed these climate uncertainties, and even then, only in a limited way. This paper offers a conceptual recommendation of an adaptive planning approach as one potential method to address these uncertainties. The approach is based on Dynamic Adaptive Pathways Planning (DAPP), which comes from the decision-making under deep uncertainty (DMDU) taxonomy. It supports planners in exploring a range of possible futures, considering policies and uncertainties, and enabling more robust decision-making.

Although novel policies will be especially important for addressing grand societal challenges, how the digital transition influences the ability of governments to adopt new policies remains unclear. In this study, the relationship between digitization and policy innovation is explored in order to understand how the two might be related. Specifically, media narratives are studied in the case of the ongoing rollout of smart metering in India to assess whether and how this instance of digital governance has been discussed in the news. To do so, 370 articles in the largest English language daily newspaper in India have been analyzed using topic modelling and sentiment analysis. Findings highlight the polysemic nature of smart metering and its ability to support highly (re-)configurable and targeted policy designs, as well as some resistance to this policy innovation thus far. Implications of the findings are discussed for theory and research on digital governance and policy innovation.

Although causal evidence synthesis is critical for the policy sciences—whether it be analysis for policy or analysis of policy—its repeatable, systematic, and transparent execution remains challenging due to the growing volume, variety, and velocity of policy-relevant evidence generation as well as the complex web of relationships within which policies are usually situated. To address these shortcomings, we develop a novel, semi-automated approach to synthesizing causal evidence from policy-relevant documents. Specifically, we propose the use of natural language processing (NLP) for the extraction of causal evidence and subsequent homogenization of the text; causal mapping for the collation, visualization, and summarization of complex interdependencies within the policy system; and graph analytics for further investigation of the structure and dynamics of the causal map. We illustrate this approach by applying it to a collection of 28 articles on the emissions trading scheme (ETS), a policy instrument of increasing importance for climate change mitigation. In all, we find 300 variables and 284 cause-effect pairs in our input dataset (consisting of 4524 sentences), which are reduced to 70 unique variables and 119 cause-effect pairs after homogenization. We create a causal map depicting these relationships and analyze it to demonstrate the perspectives and policy-relevant insights that can be obtained. We compare these with select manually conducted, previous meta-reviews of the policy instrument, and find them to be not only broadly consistent but also complementary. We conclude that, despite remaining limitations, this approach can help synthesize causal evidence for policy analysis, policy making, and policy research.

Understanding what conditions promote or hinder energy affordability in energy transitions is crucial for coal and carbon-intensive regions (CCIRs) dealing with the trade-off between phasing out fossil fuels and deepening social inequalities. While previous studies have included household and national-level conditions, this paper addresses the research gap covering regional-level conditions by drawing from regional energy governance, energy justice, and sociotechnical transition frameworks. A mixed-method approach consisting of a fuzzy-set qualitative comparative analysis and case-study analysis is applied to 14 CCIRs in Europe, Asia, and North America. Results show that energy affordability in CCIRs is influenced by combinations of regional and (inter)national conditions. Whereas the existing literature and transition policies do not differentiate between the CCI sector's transition type, this paper highlights that conditions underlying energy (un)affordability differ when the CCI sector is phased out or has the option to transition. Based on the findings, this study calls for a multi-level governance approach to alleviating and preventing energy unaffordability and recommends that policy mixes like the EU Just Transition Fund consider the different types of CCIR transitions.

Policy innovation is considered important for addressing major challenges such as climate change and the sustainable energy transition. Although policy learning is likely to play a key role in enabling policy innovation, the link between them remains unclear despite much research on both topics. To address this gap, we move beyond a binary treatment of policy innovation and differentiate policy problem innovation from policy instrument innovation and policy process innovation. Subsequently, we synthesise the literature on policy learning with the research on the multiple streams framework (MSF), a well-known lens for explaining policy innovation. Like earlier policy learning studies, we distinguish several types of learning by posing the key questions of learning, but in the context of each stream of the MSF: who learns (actors), what (beliefs), how (modes), and to what effect (ripening). This new conceptualisation clarifies the relationship of each type of policy learning to the varieties of policy innovation. Further, it indicates that policy learning is likely to result in policy innovation if and only if it influences the coupling among the three streams during a window of opportunity – through policy entrepreneurship – and not otherwise. We conclude with the implications of this study for future research on policy innovation, policy learning, and the MSF.

This editorial marks the relaunch of the Policy Innovation section of this journal, responding to the urgent need for innovative public policy amid global challenges such as climate change, economic inequality, and technological disruption. It reflects on the journal’s pivotal contributions to the subject and underscores the importance of comparative analysis in driving policy innovation. The section invites submissions that push theoretical and methodological boundaries, expand research into underexplored geographies and domains, and tackle the implications of policy innovation for equity, fairness, and justice. By broadening the scope of policy innovation, the journal aims to inspire cutting-edge, rigorous, and actionable research.