The energy consumptions growth, the upward interest for environmental sustainability and the technological evolution carry to the necessity to review the planning criteria of urban mobility systems in large cities and metropolitan areas. With this aim, new studies and projects are in progress, especially dealing with the power systems for metro-transit lines and surface electric vehicles. In this framework, the authors perform a study that, from an overview about the main energy management issues connected to the city transport, provides an innovative proposal for the design of sustainable urban mobility system: the integration of the metro-lines with surface plug-in electric vehicles. The present paper includes the energy analysis results, obtained by an application on a real case study of an home-made simulation software, describes the proposal in terms of power systems architecture and business models, pointing Out the potential advantages that its implementation could give in terms of energy saving, environmental sustainability and reduced economic impact, as a result of the maximum exploitation of existing electric power plant. (C) 2011 Elsevier B.V. All rights reserved.

In the urban mobility of big cities and metropolitan areas, the metro-transit system plays a fundamental role and it is one of the most energy-impactive. Considering the actual general upward interest for energy saving and sustainability in city transport, with the consumptions increasing and the technological evolution, new studies and projects on metro-transit lines are in progress. The aim is achieving new design proposals -including new technologies and management techniques -based on high-quality simulation models and software for energy evaluations. In this framework a study on a line of the metro-transit system of Rome has been performed. The study tasks are to provide future upgrading actions for energy saving with a reduced economic impact thanks to the maximum exploitation of existing electric power systems. The analysis principally regards the assessment of the impact of the braking energy recovering on the energy consumption. Its results point out the necessity of a revaluation of the choices on the power system design for its management, also according to the actual storage technologies, confirmed by a wide literature overview.

A simulation program, implementing a deterministic-probabilistic methodology, has been applied to an Italian railway line (Roma - Ostia Lido), whose operation is going to be changed from railway to metropolitan service. The application tasks are to point out possible critical issues of the present supplying power systems and to provide proposal about their future optimal upgrading. In order to get the real values of the main electrical parameters of electrical sub-stations (ESS) of the railway line for the simulation, an experimental survey has been performed. The paper reports the main experimental and simulation results.

The new Italian high-speed railway lines are characterised by a 2x25 kV - 50 Hz electrification standard. Train operation is carried out by the innovative ERTMS level II signalling system that is supported by audio frequency track circuits (AF-TC). The choice of the audio frequency is due to the necessity of eliminating the interference problems between 50 Hz traction currents and track circuit operation. The paper illustrates the audio frequency models, implemented in Alternative Transient Program (ATP), of both the electrification system and the track circuits. Interferences between traction harmonic currents and track circuit operation, compromising the system availability degree and the transportation regularity, are here analysed. The main results, concerning system resonance frequencies and rail current distribution, are presented and discussed.