In recent years in the European Union (EU), we have witnessed an externalization process of the provision of local government services, in order to separate the political responsibility and the direct delivery of the service. The reasons that justify this process are focused on the belief that the private sector is more efficient in carrying out economic activities, the pressure to reduce the public deficit and the public debt, the search for management systems that bypass public administration procedures, and the increase of control on local governments in auditing and accountability issues. The objective of this paper is to compare the efficiency of public and private sectors in the provision of urban transportation services. This paper shows the results of an empirical study commissioned by the Regional Audit Office of Catalonia (Spain), in order to evaluate the efficiency with which urban transportation services are delivered in the most important cities of this region. This efficiency study has been carried out using the Data Envelopment Analysis (DEA) model, multiple linear regression and logit and cluster analysis. The results allow us to conclude that, in the cities studied, exogenous factors are not relevant and the private management of urban transport service is not more efficient than public management.