Cities inhabit the most people per unit of land surface, and all these people have the need and desire to move around. On top of that, vast amounts of goods are transported into and within these cities. The extensive transportation of people and goods causes a negative influence on the environment and a transition to sustainable mobility is therefore required. Many niche-level sustainable mobility initiatives are started with the goal to support this transition. However, several of these initiatives get stranded in their process of being implemented in the mobility regime. Numerous studies have established on which aspects of mobility the most can be achieved regarding sustainability, but there is limited research performed into the inhibiting factors for sustainable mobility initiatives. This study aims at identifying the factors that negatively affect the potential influence of sustainable mobility initiatives on a regime-level transition to sustainable mobility in the Amsterdam Metropolitan Region, as well as identifying the inhibiting factors that are the probable cause of the stranding of these initiatives. In this context, niche initiatives are defined as actors (or groups of actors) aiming to implement a small-scale innovation or service, intended for a specific purpose, into the mobility regime. The regime in this research is the current market field and operation of mobility in Amsterdam. Case studies of initiatives implemented in Amsterdam and interviews with persons connected to these cases were performed to discover inhibiting factors. The interviews were semi-structured by six categories of aspects based on academic literature. The results showed recurring patterns of the need for financial, governmental and societal support by the initiatives. These results indicate that the three dominant aspects of support required by these initiatives are: sufficient financial capacity to develop and sustain the initiative with its required complementary technologies and infrastructure, governmental support and institutional embedding and societal support caused by sustainability awareness. On this basis, future initiative starters must inform and prepare themselves for these aspects to support the implementation of their initiative and governmental parties must participate in supporting these initiatives in order to support the sustainable mobility transition.