Transportation infrastructure of a country forms the backbone of economic well-being and prosperity of that nation. In order to derive this benefit and all the transportation systems must function efficiently and reliably in order to move people and freight safely and be cost effective. Any transport system, be it road, rail, air or water, should be available for maximum percentage of the time and should be safe to use. To ensure safety of such systems, proper maintenance and asset management practices must be strictly pursued. Any breakdown or accident could cost in terms of loss of revenue and assets and might even cause loss of lives. Therefore, their design, operation, and maintenance must be closely controlled and carefully executed. This is absolutely necessary to minimize the risk to the passengers, workforce and environment.

This special issue is all about this theme. Although we realize, the scope of the theme is very vast and the space is limited in order to encapsulate all the elements of variety of transport systems available today. However, the main objective of this special issue is to at least initiate a discussion in that direction through the medium of this journal. To accomplish this task, we invited Professor John D. Andrews and his colleagues to bring out a special issue of International Journal of Performability Engineering on the theme of Transport System Safety, Risk and Asset Management. Professor Andrews is Royal Academy of Engineering and Network Rail Professor of Infrastructure Asset Management in the Nottingham Transportation Engineering Centre at the University of Nottingham, U.K. The result of this initiative is the present issue.

In March 2011, the European Commission (EC) adopted a White paper titled ‘Roadmap to a single European transport area-towards building a competitive and resource efficient transport system’ (COM(2011) 144 final). This strategy involves 40 specific initiatives to build a competitive transport system that aims to increase mobility, remove major barriers, and stimulate growth and employment. Some initiatives relate to specific modes of transport: such as developing rail services or a suitable framework for inland navigation; road safety, civil aviation safety, and rail safety. Others concern transport terminals, notably the capacity and quality of airports and market access to ports. The overall aim is to reduce dependence on imported oil and to reduce carbon emissions from transport by 60 % by 2050 (with respect to the levels of 1990). The strategy also has other targets other than sustainability, such as:

• moving closer to zero fatalities from road transport accidents by 2050; or
• tripling the length of the high-speed rail network by 2050.

In October 2013, the EC put forward a new transport infrastructure policy, with a timetable to establish a core network by 2030. It is planned that this core will be composed of nine multimodal transport corridors: two north–south corridors, three east–west corridors; and four diagonal corridors. The core network by 2030 would:

• connect 94 main European sea ports with rail and road links;
• connect 38 key airports with rail connections into major cities;
• upgrade 15 000 km of railway line to high-speed networks;
• reduce bottlenecks at 35 cross-border projects.

In September 2014, the EC invited EU Member States to propose projects to use EUR 11.9 billion to improve European transport system. This is the largest ever single amount of EU funding earmarked for transport infrastructure, with funding concentrated along the nine major transport corridors.

We in India need to emulate a similar set of strategies in order to develop a viable, safe and sustainable transport system.

The elements of performance of the U.S. transportation system (which includes how reliably and safely the system serves travellers and shippers and how the movement of people and freight on the system affects the economy and the environment) are highlighted in the USDOT Strategic Plan and the Moving Ahead for Progress in the 21st Century Act (Public Law No. 112-141) under the topics of safety, state of good repair, economic competitiveness, environmental sustainability, and liveable communities. Some of the facts worth noting are:

• Traffic congestion in the US costs a commuter, on average, 34 hours in delay and 14 extra gallons of gasoline per year-roughly double the costs two decades ago.
• All modes of freight transportation experience substantial congestion. Truck congestion alone cost $23 billion in wasted fuel and hours of delay in 2010.
• While fatalities have declined over the last four decades (There were over 50,000 motor vehicle fatalities annually between 1966 and 1973), transportation still accounts for nearly 35,000 lives lost and over 2.2 million injuries each year (2011).The number of injured were estimated 3.2 million in 1990.
• The transportation sector accounts for 70.2 percent of total petroleum consumption in the United States. In 2011, the transportation sector accounted for about 27.9 percent of total U.S. energy consumption.
• Transportation is the single largest sector generating greenhouse gas emissions, accounting for about one-third of the U.S. total; transportation's 1.8 billion metric tons of carbon dioxide emissions in 2010 is down from 1.9 billion metric tons in 2005.

According to the World Health Organization, road traffic injuries caused an estimated 1.24 million deaths worldwide in the year 2010, slightly down from 1.26 million in 2000. That is one person is killed every 25 seconds. Only 28 countries of the world, representing 449 million people (7% of the world’s population), have adequate laws that address all five risk factors (speed, drink-driving, helmets, seat-belts and child restraints). There are large disparities in road traffic death rates between various regions of the world. The risk of dying as a result of a road traffic injury is highest in the African Region (24.1 per 100 000 population), and lowest in the European Region (10.3 per 100 000). According to WHO report of 2013, the road accident fatalities per 100000 inhabitants per year in some of the countries of the world are as follows: China-20.5, India-19.9, Russia-18.6, U.S.A.-11.6, Italy-6.2, France-4.9, Japan-4.8, Germany-4.3, and U.K.-3.5, Israel -3.3, Denmark- 3.0, Sweden-3.0, and Norway-2.9. Although for most of these countries, the figures given above are for the year 2012 except for France and Germany (2013), India (2011) and China (2010). Half of the world’s road traffic deaths occur among motorcyclists (23%), pedestrians (22%) and cyclists (5%) - i.e., vulnerable road users- with 31% of deaths among car occupants and the remaining 19% among unspecified road users. Young adults aged between 15 and 44 years account for 59% of global road traffic deaths and 77% road deaths are among men. Road Safety is a major societal issue in European Union. In 2011, more than 31,500 people died on the roads of the European Union (EU), i.e., the equivalent of a medium town. For every death on Europe's roads, there are an estimated 4 permanently disabling injuries such as damage to the brain or spinal cord, 8 serious injuries and 50 minor injuries. EU targets to reduce fatalities to nearly half by 2020. Road safety is also a major issue in India that needs special attention as there's one death reported every 4 minutes on the streets of India. Nearly 500,000 road accidents were reported in 2013 in which more than 100,000 people lost their lives. A large chunk of the victims were aged between 30 and 44 years.

According to rail road accident data from the Office of Safety Analysis, Federal Railroad Administration of US Department of Transportation, there were a total of 1704 rail accidents in 2012 of which 1256 were derailments, 159 were collisions resulting in 9 fatalities and 283 injuries. Relative figures for India which has 64000 km of rail network are not known accurately but through newspaper reports at least over 15000 persons died in rail accidents every year and some 20 million people travel each day in India by trains in a nation of 1.2 billion. A high level committee was set up by the Government to review the safety of rail road network and suggest measures to improve it.

Regarding data on aviation safety, the Jet Airliner Crash Data Evaluation Centre (JADEC) provides global safety analysis about commercial airlines since 1989. The German founders Jan-Arwed Richter and Christian Wolf have written a number of books about aviation accidents- JACDEC books. Since 2002 JACDEC publishes an annual ranking of the "Safest 60 Airlines". The index rating, JACDEC distinguishes whether an event is a total loss or a serious incident: Both will be recorded in JACDEC Database, but in the final weighting a total loss counts considerably more. The term "total loss" means that any repair costs of accident damage exceeds the residual value of the aircraft or if the aircraft was totally destroyed. JACDEC include only flights where paying passengers are on board. Therefore all freight – ferry, training of maintenance flights are disregarded. The JACDEC Safety Index is developed from their own database. To arrive at the rankings, JACDEC claimed that it culled data on air crashes and fatalities during the last 30 years and factored in international safety benchmarks. Furthermore, since 2013, JACDEC takes into account the level of transparency the governing authority has. The Centre also monitors current safety occurrences and provides updates on airline safety issues. JACDEC includes a time factor, which increases the effect of recent accidents and lessens the impact of those in the past. Among the safest airlines in 2014 ranking is Air New Zealand followed by Hong Kong-based Cathay Pacific and the 91-year-old, government-owned Finnair. The only carrier older than Finnair that made it to the top 10 ranks was 1919-born British Airways at 6^th position. Etihad Airways, which has been around for just about 10 years and was one of the youngest airlines in the list, is deemed the eighth safest. No US-based airline figured in the top 10. India's Jet Airways was at 35^th spot and Air India placed at 57^th spot. According to the ranking, the 54-year-old China Airlines which had 755 fatalities since 1982, the highest in the world is placed at 58^th position after Air India. In the last 30 years, Air India has had only one crash-that of Air India Flight 182 on June 23, 1985-which ended in a hull loss and 329 deaths. But that crash was as a result of a terrorist action, not poor safety. After China Airlines, Korean Air suffered the second-most fatalities at 687; and yet, it figures at 52^nd rank in 2014 list. At the same time, the carrier suffered eight "hull loss" accidents, which was less than Aeroflot and American Airlines' 10 each but they figure at 37^th and 41^st ranks respectively in the list. Obviously, some airlines question this safety ranking.

Regarding safety of waterborne transportation system related to vessel casualties and damage to property, the figures provided for 2012 by the Office of Investigation and Analysis, U.S. Coast Guard, U.S. Department of Homeland Security are as follows: Fatalities -33; Injuries -141; Accidents -5298; Vessels -7972; and the properties damage is Dollars 100.4 million. In Canada, Transportation Safety Board (TSB) keeps annual record of marine safety and it covers commercial vessels, which include all vessels registered or licensed to operate commercially. In 2012, 286 marine accidents were reported to the TSB, down from the 2011 total of 326 and the 2007–2011 average of 391. Over the past 10 years, nearly 90% of marine accidents were shipping accidents, while the remainder were accidents aboard ship. In U.K., Marine Accident Investigation Branch (MAIB) keeps all the records of accidents. The Merchant Shipping (Accident Reporting and Investigation) Regulations 2012 require Masters, Skippers and Owners of vessels to report accidents. In addition, this duty to report accidents to the MAIB extends to harbour authorities, inland waterway authorities, and the Maritime and Coastguard Agency.

Lastly, I would like to thank Prof. John D. Andrews, Dr. Rasa Remenyte-Prescott of Nottingham University and Dr. Lisa M. Jackson of Loughborough University, U.K. for formulating and bringing out this special issue And our sincere thanks are due to the referees who assisted in timely reviewing the manuscripts and to all the authors whose articles are included in this issue.

Transport systems and infrastructure form critical elements of modern society. It is essential that such systems operate efficiently and reliably in order to move people and goods to their destinations in a safe and cost effective manner. When such systems experience operational failures they cause disruption and inconvenience, and in the worst cases can result in injuries and fatalities. As the population increases, the demands on the transport systems also increase.

Any transport system, be it road, rail, air or water, is more efficient the larger the percentage of its time it is operational and therefore generating an income. A difficulty with this operating practice is scheduling the times for essential preventive maintenance. The proper maintenance practices will minimise the occurrence of breakdowns necessitating reactive maintenance. An added consideration is that many transport systems feature aging infrastructure.

From the safety point of view, whilst transport systems usually have high levels of safety, their design, operation, and maintenance have to be controlled adequately in order to ensure this state. Modelling techniques should be used to predict the effectiveness of the asset management strategy employed for transport systems and also to predict the risk to the passengers, workforce and general public that they pose.

This special issue contains a number of articles that are focussed on transport system asset management, reliability and safety.

The first paper by Rama and Andrews investigates the advantages of analysing the railway network as a multi-asset system, when a Petri Net model is developed and analysed using the Monte Carlo simulation method. The model is used to predict the network performance and obtain the information to support asset management decisions.

The second paper by Fink et al. propose an algorithm of Deep Belief Networks to predict operational disruptions caused by train door systems and demonstrate its performance using a European railway fleet data.

A road maintenance management system is presented in the third paper by Yang et al., where an optimal strategy of maintenance and reconstruction works on a highway network can be found using the method of Genetic Algorithms. Pavement age gain models are developed for the evaluation of pavement condition over time due to maintenance.

In the fourth paper by Hackl et al. focuses on risk evaluation of infrastructure networks due to natural hazards. Due to the complex interdependency of the infrastructure systems such events, albeit rare, can have a devastating impact. The authors propose to use an overarching risk assessment process across a number of modules for individual systems which interact and the process is demonstrated in a case study for an example region in Switzerland.

The fifth paper by Stoop and van Kleef considers air transport systems as socio-technical systems and suggests that the increased complexity and interdependency of the infrastructure systems requires novel notions for reliability, control over operational performance and safety assessment. Incorporating the operator performance characteristics during the response to failures is of vital importance in capturing the overall behaviour of such systems and in dealing with potentially catastrophic consequences.

Finally, in the sixth article, van Dongen offers a perspective of maintenance engineering when the calculations of life expectancy of an asset are integrated in the initial design of new assets and the maintenance and modernisation of the current ones. Real-time asset condition monitoring furnishes maintenance teams with more accurate information and supports proactive dynamic maintenance scheduling, which poses a challenge in terms of maintenance logistics but can lead to a reduced number of unexpected failures. Overall, these articles present some of the latest developments and future trends in the area of asset management, reliability and safety across the different transport sectors.

The Guest Editors would like to thank all of the authors for their contributions in this special issue and the reviewers for their time in providing the authors with constructive feedback. We would also like to thank the Editor-in-Chief, Professor Krishna B. Misra, and the editorial team who worked on the publication of this special issue.

ABOUT THE GUEST AUTHORS

Rasa Remenyte-Prescott is The Lloyd’s Register Foundation Lecturer in Risk and Reliability Engineering in Nottingham Transportation Engineering Centre at the University of Nottingham (which helps protect life and property by supporting engineering-related education, public engagement and the application of research). Rasa gained BSc and MSc degrees with distinction in mathematics from Kaunas University of Technology, Lithuania. Following this Rasa undertook her Doctorate research at Loughborough University on systems reliability modelling of non-coherent systems using the Binary Decision Diagram technique. Rasa’s research interests involve reliability modelling techniques for engineering systems and healthcare safety, infrastructure asset management methods for railways and highways and fault diagnostics techniques. She is the author of around 30 research papers on these topics.

Email: Email:r.remenyte-prescott@nottingham.ac.uk

John D. Andrews is the Royal Academy of Engineering and Network Rail Professor of Infrastructure Asset Management in the Nottingham Transportation Engineering Centre at the University of Nottingham, U.K. He is also Director of The Lloyd’s Register Foundation Centre for Risk and Reliability Engineering. Prior to this position he worked for 20 years in the Department of Aeronautical and Automotive Engineering at Loughborough University where his final post was Professor of Systems Risk and Reliability. The prime focus of his research has been on methods for predicting system reliability in terms of the component failure probabilities and a representation of the system structure. Much of this work has concentrated on the Fault Tree technique and the use of the Binary Decision Diagrams (BDDs) as an efficient and accurate solution method. Recently attention has turned more the degradation modelling and the effects of maintenance, inspection and renewal on asset performance. He is the author of over 200 research papers. He is also one of the Editors-in-Chief of IJPE. He is also Editor-in-Chief of Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability.

Email: John.Andrews@nottingham.ac.uk

Lisa Jackson (Ph.D.) is a Senior Lecturer in Risk and Reliability, in the Department of Aeronautical and Automotive Engineering, Loughborough University, England since 2010. She has taught at this university since 2001. She has published extensively in the area of Reliability and Risk in several international Journals. Her research interests include Applications of Reliability Methods for enhanced reliability performance, Fault Diagnostics and Prognosis, Crime Reduction through Demand Modelling and Positioning, Vehicle Safety and Hazard Analysis. She is on the Editorial Board of the International Journal of Performability Engineering and of the IMechE Part O: Risk and Reliability Journal.

Email: L.M.Jackson@lboro.ac.uk

In the railway industry asset management decisions are focused on the maintenance, enhancement and renewal of assets in order to ensure a required level of dependability and improvement in services at the lowest whole life costs. To achieve these objectives system lifecycle models, rather than individual asset models, offer a greater advantage. The paper presents a modelling approach developed for constructing multi-asset system models to support well-informed railway infrastructure asset management decisions. The models are built using the Petri Net formalism and are analysed by a means of Monte Carlo simulations. A specific example of the railway superstructure model is presented. Its simulation results demonstrate the superiority of the system-wide model against individual asset models in terms of its accuracy in predicting the superstructure (system) performance and information available to support asset management decisions. Furthermore, by using the multi-asset system model interdependencies among maintenance regimes of different assets and different parts of the infrastructure can be modelled.

In this paper, we propose to apply deep belief networks (DBN) to predict potential operational disruptions caused by rail vehicle door systems. DBN are a powerful algorithm that is able to detect and extract complex patterns and features in data and has demonstrated superior performance on several benchmark studies. A case study is shown whereby the DBN are trained and applied on real case study from a railway vehicle fleet. The DBN were shown to outperform a feedforward neural network trained by a genetic algorithm.

This paper presents a new pavement management system (PMS) to achieve the optimal pavement maintenance and rehabilitation (M&R) strategy for a highway network using genetic algorithms (GAs). Optimal M&R strategy is a set of pavement activities that both minimise the maintenance cost of a highway network and maximise the pavement condition of the road sections on the network during a certain planning period. NSGA-II, a multi-objective GA, is employed to perform pavement maintenance optimisation because of its robust search capabilities and constraint handling method that deal with the multi-objective and multi-constrained optimisation problems. In the proposed approach, both deterministic and probabilistic pavement age gain models are utilised for evaluating the evolution of pavement condition over time because of their simplicity of application. The proposed PMS is applied to a case study network that consists of different kinds of road sections. The results obtained indicate that the model is a valuable toolbox for pavement engineers.

In Europe, extreme natural hazard events are not frequent but due to the complex interdependency of the infrastructure systems these events can have a devastating impact in any part of Europe. Protection against the impacts of natural hazards must be guaranteed for people to work and live in a secure and resilient environment. People who manage infrastructure have to handle these risks. The proposed overarching risk assessment process is constructed in a way so that computational support can be constructed in modules. Therefore, each module interacts with other modules by receiving and delivering information. The content of the modules depends on the established context of the risk assessment process. The use of the overarching risk assessment process is demonstrated by using it to evaluate infrastructure related risk due to natural hazards for an example region in Switzerland.

The increased complexity of infrastructural and transportation systems makes those systems less tractable, requiring new notions for reliability, control over operational performance and safety assessment. To this purpose, the contribution elaborates on the principles offered by the Cynefin notion as a guide in landscaping system complexity and dynamics. Beyond the normal and predictable behavior of operators by mathematical assessment of their reliability and procedural control over safe performance of the operator, this contribution emphasizes two new approaches. The scope of this study is to reconsider the notion of human error as an adequate operator response to system failure under a variety of operating conditions. It introduces operator variance, resilience and transitions across system states and mental modes as an operationalization of the notion of Good Airmanship and Good Seamanship. On one hand a design oriented expansion of the safety envelope with respect to resilience is argued, while during operations at the performance level of the operator, the conventional Skill-Rule-Knowledge based model of Rasmussen is adapted, adding a intrapersonal reflex level and a interpersonal crew coordination level. Such an augmented ability to recover from the unanticipated is demonstrated for the aviation sector.

In the past, assets were designed in large construction teams but companies in recent decades focus more and more on their core activities. The management of capital goods is being organized in the (supply) chain of owners, users, manufacturers, research institutes, IT, service providers and so on.
The complexity of modern systems (e.g., mechatronics) and sustainability issues have placed more pressure on cooperation: openness, interaction and stability in the relationship foster joint innovation in product, process and technology. Focus on opportunities rather than risks makes this cooperation successful.
With the operational processes in good shape it is to show where the technical characteristics of the assets fail. Technical “on the spot” support is important to develop understanding between the maintenance and the production organizations, and establishing a sense of urgency in their cooperation: first to analyse the actual fault behaviour of the equipment and to solve short-term problems and secondly to take structural measures.
In the coming years, real time monitoring facilitates maintenance with more accurate information than before. Proactive dynamic maintenance scheduling reduces the number of unexpected failures.