This paper examines the effect the Gothenburg congestion tax, which was implemented in 2013, has had on the usage of public transportation. The aim of the policy is to reduce congestion, emissions and to finance public transportation infrastructure. The analysis contains panel data over the years 2010 - 2016 in order to measure the changes for the corresponding period of time. This research will contribute to existing research with a new approach since the instrument for controlling congestion is recently implemented, and the empirics are underdeveloped within this field. The difference in difference analysis is executed to isolate the impact of the introduced congestion tax. Gothenburg act as a treatment region, and Växjö act as a control region. Växjö is used as a control region due to limitations in the collection of data; differences between the selected regions are present and are essential to recognize. Significant differences are found in the population, controlled by a generated ratio between monthly commutes and population. Parallel trends are analyzed to increase the validity of the approach and estimated to be held constant during this period. Results show increased usage of public transportation in Gothenburg by approximately five trips per citizen monthly, due to the implementation of the congestion tax. Citizens in Gothenburg avoid getting additional taxied by correcting their type of transit.