Resumen
Congestion in the urban transport network is common not only in large agglomerations, but also in medium-sized cities in all countries that are characterized by a high level of socio-economic development. Traffic congestion has negative impact on economic, social, and environment development. The costs of congestion are borne by all users of the transport system, both drivers, passengers, entities providing transport services, as well as enterprises using freight transport services.The purpose of the article is to discuss the results of the study on the impact of congestion on the costs of public transport in a medium-sized city. The research method consisted in the analysis of vehicle road cards, fuel consumption statements for buses belonging to the Municipal Transport Company in Starogard Gdanski and the examination of real bus travel times and the scale of delays caused by congestion on individual lines.The analysis of the data shows that the company bears much higher costs of fuel consumption, and passengers are exposed to bus arrivals and departures inconsistently with the timetable, prompting them to opt out of public transport services. This results in lower revenues from ticket sales and deterioration of the company's financial result.