Effects of rolling stock unavailability on the implementation of energy-saving policies: A metro system application

The recent world policies have shown the necessity of implementing suitable strategies, especially in urban contexts, in order to promote more sustainable transportation systems. In this context, the rail-based systems allow to achieve sustainable goals according to a threefold effect: reduction in externalities (such as congestion, accidents, air and noise pollution), increase in efficiency (in terms of operational cost per real/potential carried passenger), and delocalization of energy production centres (large industrial plants out of population centres producing with optimal yields). Positive environmental aspects of the rail and metro systems may be further amplified by implementing Energy-Saving Strategies (ESSs) based on the adoption of suitable driving profiles and/or the installation of onboard/wayside recovery devices. In this context, we investigate the effects of rolling-stock unavailability (for breakdowns, maintenance or under-sized fleet) on the effectiveness of ESSs within a multi-objective framework which combines the reduction in energy consumption with a passenger-oriented perspective. A real metro line in the south of Italy has been analysed as case-study in order to show the feasibility of the proposed approach.