The development of sustainable transport is a priority in cities. It should aim to increase the number of trips made by public transport while minimizing social costs and the negative impact on the environment. The intensive development of cities from industrial to service-oriented and the phenomenon of suburbanization require changes in public transport services. However, often, operators do not change existing lines and stops or timetables justifying it with passenger habits. This approach may cause a discrepancy between the accessibility of public transport services and the demand for these services. Therefore, planning and improving the public transport system should be based on careful analyses. There are various approaches to this problem. The article presents a method to assess accessibility of public transport services using spatial and temporal analysis. The proposed method is based on dividing the area into basic fields and then, using appropriately selected measures, each field is assessed in terms of both the current level of accessibility of public transport services and the potential transport demand. A comparative analysis with the use of spatial tools indicates the degree of matching of these values and enables the identification of areas (basic fields) in which improvement of public transport services is required. For the proposed method, a case study was carried out for the city of Czeladź, located in Metropolis GZM in the southern part of Poland. The method can support decision making to improve the current public transport system.