Alejandro Ortega Hortelano

Resilience engineering: theory and practice in interdependent infrastructure systems

The economy and well-being of modern societies relies on complex and interdependent infrastructure systems to enable delivery of utilities and movement of goods, people and services. This complexity has resulted in an increased potential for cascading failures, whereby small scale initial failures in one system can result in events of catastrophic proportions across the wider network. Resilience and the emerging concept of resilience engineering within infrastructure are among the main concerns of those managing such complex systems. However, the disparate nature of resilience engineering development in various academic and industrial regimes has resulted in a diversity of definitions and characterisations. These are discussed in this paper, as are the commonalities between sectors and between different engineering disciplines. The paper also highlights the various methodologies used as part of resilience engineering implementation and monitoring, current practices including existing approaches and metrics, and an insight into the opportunities and potential barriers associated with these methodologies and practices. This research was undertaken for the Resilience Shift initiative to shift the approach to resilience in practice for critical infrastructure sectors. The programme aims to help practitioners involved in critical infrastructure to make decisions differently, contributing to a safer and better world.

Price Elasticity of Demand on the High-Speed Rail Lines of Spain: Impact of the New Pricing Scheme

Reduced travel time, regional cohesion, economic development, and environmental benefits were some of the reasons given to develop a high-speed rail (HSR) network in Spain. Since the first high-speed line in Spain opened in 1992, HSR has been a part of the travel experience, despite recent concerns raised about the lack of demand and low occupancy rates of HSR trains compared with those in other countries. In February 2013, Renfe Operadora, Spain’s state-owned transport company, implemented a new pricing scheme, which reduced ticket prices by at least 11% and introduced flexibility in their purchase. In this research, the effects of the new scheme were analyzed, and the impact on the shift in transport modes was substantiated through consideration of a discrete choice model. As a consequence of this policy, occupancy rates were increased hugely. Although apparently ticket price was not regarded by users as the main reason to travel by HSR, the price elasticity of demand turned out to be high. Given the transport modes that competed with HSR, the effects were quite different. For short routes connecting small- and medium-sized cities with big metropolitan areas, growth in demand was achieved at the expense of the car and the bus, whereas for long routes connecting large cities in which air transport was available, the growth occurred mainly at the expense of air transportation, and induced demand also was triggered. Finally, when the owner of the infrastructure and the train operating companies were managed by the government, the rail infrastructure fee policy set may have prompted unfair competition with other transport modes.

REDUCING MAINTENANCE COSTS FOR BALLASTED TRACK: EVIDENCE FROM BRITAIN

Over the last twenty years, the railways in Britain have seen rapid growth, with patronage doubling and the level of train service increasing by 50%. However, these successes have also led to challenges. In particular real unit costs are estimated to have increased by 50%, with particularly marked increases in infrastructure renewal and enhancement costs. Against this background, the University of Southampton have been leading the Track 21 and Track to the Future projects, funded by the Engineering and Physical Sciences Research Council. These projects are assessing how to make ballasted track systems more durable given higher traffic levels, and how to reduce the costs of maintenance and renewal. Track 21 considered a number of engineering interventions of which this paper focusses on one, Under Sleeper Pads (USPs). The cost implications of this intervention are assessed for the South West Main Line using an industry-specific model, VTISM (Vehicle Track Interaction Strategic Model), adapted in two ways. First, the results of laboratory experiments from specialist test rigs are incorporated into the model. Secondly, the wider effects of increased reliability, improved ride quality and reduced vibration are also considered within a costbenefit analysis framework. It is found that USPs can lead to substantial financial savings and, depending on assumptions concerning noise impacts, are likely to have substantial wider social benefits.