Zero-emission buses (ZEBs) are considered a vital element in the transition to a more sustainable (urban) transport system. Both battery-electric and hydrogen fuel cell buses do however face significant barriers to large-scale implementation. These barriers, e.g. high investment costs and limited driving range, are generally regarded as exogenous technological barriers which are beyond the sphere of influence of actors in the public transport sector. In this paper we question this assumption and therefore we look at the role of institutions in public bus transport. Based on a series of interviews with stakeholders in the Dutch public transport sector we argue that various regulative, normative, and cognitive institutions discourage the use of zero-emission buses in public transport. We conclude with several suggestions for institutional innovation to increase the chances for these buses.

The dynamics of protection in the context of socio-technical niches have remained under-researched. In this paper we conceptualise the process of policy learning in the context of transitions. We show that a variety of actors inside and outside a technological niche have to learn about the implications and effects of regulations aimed at protection of niches. We analyse this process of policy learning in two cases: high-need drugs and electric vehicles. We conclude that both regulators and the regulated need to learn about the width and depth of protection measures, their duration, the specific set of tools used, and their legitimisation. A crucial issue of implementing protective regulation is the question on what level of aggregation protection measures need to be applied. Learning is often part of the negotiation process between the protector and the protected, but in many cases learning only takes place after policies have been implemented.

In the socio-technical transitions literature, local niche projects have been described as sources of knowledge, experience, actor networks, and (positive) expectations. Local niches and local designs can however also become stumbling blocks when local designs are non-compatible with an emerging global standard. In this paper we study the emergence of standards for electric vehicle recharging plugs to answer the question whether and how local niches and their outcomes may hamper the process of niche aggregation. Our analysis shows that distinct local recharging plug standards have emerged for both regular and fast charging. Especially the standards for regular charging are clearly designed to comply with local regime rules and that these rules have thus prevented the development of a global standard. With our analysis we show that the local context may indeed be so intrusive that it inscribes itself irreversibly in technical designs and standards and hence lead to local lock-ins that prevent further aggregation. Even more so, we recognize a tension between the need for local niche projects to comply with local rules and the need for the global niche to break free from such local rules in order to define universal designs instead.