This paper first discusses the data needs of the European Transportation Information System (ETIS), focusing on the two sets of accounts needed to monitor transportation and answer recurrent and permanent sets of policy questions. These types of accounts are economic (indicators of the evolution of transportation within the macro-economies of the member states) and network-related (reference indicators of the state of networks and of their accounts, presumably for reference years). ETIS methods and models are then discussed with reference to possible biases in data design, research, and other issues.