Evaluation of travel demand impacts in the case of rail system failure

Rail or metro systems are generally characterised by high performance in terms of maximum travel speeds and/or reduced headways between two successive convoys. However, in the event of breakdowns, since faulty trains cannot usually be overtaken and their removal could pose extreme difficulties especially in metropolitan systems with two separate tunnels, re-establishing the regular service could involve inconveniently long travel times. Hence, our proposal is to analyse effects on travel demand of different levels of degraded services in the case of metro system failure in order to define the best strategy to adopt so as to minimise user discomfort. In particular, we propose to simulate a rail system through the interaction of four models (failure, service, supply and travel demand) by extending ideas proposed elsewhere in the literature. Finally, the proposed methodology is tested in the case of an Italian metro system by providing for each failure scenario the selection of the best strategy to minimise impacts on users. Initial results show that interactions among rail system components (infrastructure, rolling stock, signalling and timetable) and travel demand are complex, and therefore the optimal strategy to be implemented may be affected not only by rail system breakdowns but also by travel demand conditions.