This paper analyses the integration of social considerations into public transport planning. It addresses the challenge of balancing social benefits against objectives such as efficiency and cost minimization. Through a literature review, this paper examines methods for assessing public transport accessibility for potentially disadvantaged groups and identifies knowledge gaps in existing research. The analysis reveals a predominant focus on post-implementation (ex-post) accessibility assessments and a lack of research examining potential impacts (ex-ante) during planning stages. Furthermore, the paper identifies a lack of research on how to weigh social benefits against other more conventional objectives such as efficiency and cost minimization and also against environmental considerations. Research usually proposes changes ex-post based solely on a desire to improve accessibility for potentially disadvantaged groups. Therefore, there is a need for more research on how to manage conflicting interests in planning, for example through composite methods. The paper also highlights the tendency of research to overlook the practical usability of methods developed. The relevance of methods to policy makers and planners responsible for planning public transport systems remains largely unexplored. To develop practically useful methods, research needs a better understanding of the norms governing planning practices. It is common to discuss how the mobility needs of potentially disadvantaged passenger groups should be met in isolation from policy contexts. More research is needed about how the potential tensions between social, economic, and environmental considerations play out in public transport planning practices. All of this leads to a risk of a theory-practice gap, marked by a disconnect between research and the practical needs of the public transport providers. By proposing a more nuanced research approach that better reflects the complexity of real-world planning and the different needs of user groups, research can enable public transport planning for what we term 'sustainable accessibility'.