The purpose of this study is to deepen the understanding of what are the underlying reasons for the increasing cost of public transport in general and bus services in particular in a Swedish context. Data were collected through in-depth interviews with managers at the bus operators as well as the authority organizations. This paper contributes by identifying nine categories that can be the dominating factors behind the increasing costs of public bus services in Sweden. The identified categories of cost drivers are; of traffic appearance (peak times), greening of buses, age requirements, the contract period, the accessibility customization, special requirements on buses, collective agreements (working time regulation), tendering and contracting process, and finally, counterproductive political governance. It can be concluded that many of the cost drivers originate from the circumstances of the process of public procurement, such as different demands for different regions in Sweden as well as the trade-off between the bus operators' wishes for higher flexibility in the contracts and the traffic authorities' fear of more risks and thereby higher bids in the end. (C) 2016 Elsevier Ltd. All rights reserved.