The overall aim of the thesis is to investigate the knowledge problem in regional public transport planning. The knowledge problem is twofold. How do transport policy arrive at the desirable actions they take and how do they assess the alternatives, and what can we say about the contributions of already implemented transport schemes. Paper 1 explores how policy objectives in regional public transport are translated into action and to investigate how public transport measures are evaluated. Paper 2 presents a case study of Spårväg syd, a light rail project in Stockholm, with the ambition to understand the use of appraisal tools and discuss how these can be improved. Paper 3 investigates the links between accessibility, as well as the composition of accessibility and real estate values. Paper 4 analyses the causal effect of a train station on local labour income among current residents as well as the labour income of the residents that the place attracts. Finally, paper 5 explores the association between the accessibility that train stations provide and local labour income more broadly across Sweden. For paper 1, the results indicate that decision-makers ask for knowledge on ongoing trends such as patronage and market share in relation to all motorized transport, an increased interest in understanding the impacts of transport on society, the strategies of PT are connected to long term regional ambitions. Paper 2 highlights that particular projects are tightly connected to long term ambitions. Spårväg syd was on the agenda long before a formal cost-benefit analysis was conducted. The project is also tightly connected to political goals of land-use development. The findings from paper 3 reinforce the evidence that real estate values are positively associated with accessibility. Also, the paper finds that the composition of accessibility, namely the degree to which the accessibility is built up by one or several modes of transport, is positively associated to real estate values as well. The policy implication of this finding is that transport appraisal could add assessments not only of marginal accessibility changes, but also the marginal change in the composition of accessibility. The results from paper 4 indicate an absence of a causal link between train stations on local labour income. Both in terms of the longitudinal analysis and the spatial sorting analysis. For paper 5, accessibility through the national railway network was found to be associated with local labour incomes. The thesis increases the evidence of effects of transport on income and real estate prices. Moreover, the thesis concludes that regional public transport planning seems to be subject to different motivations and trade-offs depending on project and context, which complicates the seeking for a universal appraisal procedure.