In practice, input congestion effects appear in railway transport due to the difficulties of disposing of unnecessary input factors. This study measures the output-oriented technical efficiency and input congestion with consideration of categorical variables for railway transport by using the DEA extension approach. The empirical results from 24 European railway companies show that in 12 railways, the presence of weak congestion can be proved. Based on the results of identifying the source(s) of input congestion and further determining its amount, one can obtain more insights into railways’ operation and thus propose more effective strategies for improvement.