Designing for safety: the ‘free flight’ air traffic management concept

This paper describes the conceptual design and validation of an air traffic management (ATM) concept and the role the safety and human factors played in this design and validation process. The free flight (FF) concept is characterised by being a direct route concept where the pilots, instead of the air traffic controller, are responsible for the separation assurance. Moving this task to the cockpit has consequences for the man machine interface in the cockpit, which needs to be modified to accommodate this new task (micro level design). On top of that, a set of rules and procedures are required to ensure an efficient and safe traffic flow (macro level design). Both the micro and macro aspect of this design are intertwined and require an accurate tuning to arrive at an overall acceptable solution. Both micro-level (flight simulator) experiments and macro-level (traffic simulations) experiments have been conducted to investigate the feasibility of this concept after optimising the initial conceptual design.     

Managing product reliability in business processes ‘under pressure’

Product reliability is often seen as a product attribute. Models with different degree of sophistication analyze and predict the reliability of a product as a function of the internal structure (such as components and their relation). The practical relevance of these models, in relation with the (business) processes in which the related products are actually used, is not often addressed. Different types of reliability issues, however, can be relevant for products in different industrial contexts. This paper will present a classification model to describe different business processes, based on the degree of product innovation. It will also propose a taxonomy that can be used to classify different types of reliability problems. As this paper will demonstrate, only certain combinations of reliability problems are relevant for certain business processes. It will also show that, given certain technology trends, some combinations will become more relevant in the future. The final part of this paper will demonstrate that especially for these combinations many of the existing reliability analysis and prediction methods can be considered inadequate.     

A new perspective on Renn and Klinke's approach to risk evaluation and management

In this paper we discuss Renn and Klinke's approach for risk evaluation and selection of risk management strategies. The main focus in the discussion is the foundational basis and the understanding of what risk is, and how a different foundational basis may simplify and improve the characterization of risk. We will present and discuss an alternative set of characteristics, and give some recommendations with respect to selection of risk management strategies based on different values or magnitudes of these characteristics. We believe that the main focus when describing and managing risk should be the potential consequences, represented by observable quantities, and the uncertainty related to their future values.     

Complicating the ‘logic of design’

A ‘logic of design’ was outlined by March in 1976. Since then it has gained wide acceptance among designers and recently has been used in several knowledge-based systems of design. This paper makes a suggestion for extending the model by taking into consideration the logical nature of the laws in the argument form. This focus on the logical nature of laws brings out interesting and subtle differences in the inference process which are lost in the current analysis. It also results in some interesting complications. It means that it is no longer adequate to talk of the three phases of design — performance prediction, knowledge acquisition, and design generation — in the simple categories of deduction, induction and abduction, respectively. In particular, it means that performance prediction is not necessarily (or even usually) a deductive inference.     

Traffic accident statistics and risk perceptions in Japan and the United States

Several recent studies have concluded that Japan and the US have different risk cultures. This study examines the actual risk environments faced by citizens in the two countries, in the domain of traffic safety, as a possible source of differences in risk perceptions. The study contrasts traffic-accident risks from several points of view (e.g. car drivers, motorcyclists, bicyclists and pedestrians) and risk statistics (e.g. death rates, relative fatality risks, and accident lethality). Results clarify the traffic risks in the two countries and confirm their potential for explaining cross-national differences in risk perceptions.     

盐岩能源地下储备库群风险综合评价与管理体系

利用盐岩洞穴进行能源地下储备是我国能源储备的重点战略部署方向。我国盐岩地层埋深浅,呈层状分布,且夹层较多,地质条件相对复杂,增加储库灾变的可能性,因此建立一套盐岩能源地下储备库群风险综合评价和管理体系尤显重要。根据盐岩地下储库群灾变事故的统计结果,获取了盐岩地下储库的主要风险因子,对库群风险进行了辨识。建立了盐岩地下库群风险评价方法和风险分级标准,通过数值模拟方法对失效概率进行了核算,评价了金坛盐岩库群风险等级,并通过模型试验对结果进行了验证,开发了基于计算机网络技术的盐岩地下库群风险信息管理与评估系统,建立了盐岩能源地下储备库群风险综合评价和管理体系。     

Response to Yellman & Murray's comment on ‘The meaning of probability in probabilistic risk analysis’

In their comment on a recent contribution of mine, [Watson, S., The meaning of probability in probabilistic safety analysis. Reliab. Engng & System Safety, 45 (1994) 261–269.] Yellman & Murray assert that (1) I argue in favour of a realistic interpretation of probability for PSAs; (2) that the only satisfactory philosophical theory of probability is the relative frequency theory; (3) that I mean the same thing by the words ‘uncertainty’ and ‘probability’; (4) that my argument can easily lead to the belief that the output of PSAs are meaningless. I take issue with all these points, and in this response I set out my arguments.     

The coincidence site lattice and the ‘sigma enigma’

This paper focuses on the most appropriate use of electron back-scatter diffraction (EBSD) post-acquisition analysis for categorisation of grain boundaries in polycrystals. A brief survey of the early literature shows that the most meaningful reference structure for grain boundaries in polycrystals is periodicity in the grain boundary surface, rather than the misorientation-based coincidence site lattice (CSL) and Σ notation. However, use of the CSL is convenient to the experimentalist. It is therefore suggested that wherever possible, misorientation data, obtained by EBSD mapping and classified according to CSL types, should be supplemented with other, more detailed information to aid analysis.     

A simple approximate expression for finite life fatigue behaviour in the presence of ‘crack‐like’ or ‘blunt’ notches

In this note, we explore the possibility of simple extensions of the heuristic El Haddad formula for finite life, as an approximate expression valid for crack‐like notches, and of the ‘Luká? and Klesnil’ equation for blunt notches. The key starting point is to assume, in analogy to the Basquin power‐law SN curve for the fatigue life of the uncracked (plain) specimen, a power law for the ‘finite life’intrinsic El Haddad crack size. The approach has similarities with what recently proposed by Susmel and Taylor as a Critical Distance Method for Medium‐Cycle Fatigue regime. Reasonable agreement is found with the fatigue data of Susmel and Taylor for notches, and in particular the error seems smaller in finite life than for infinite life, where these equations are already used. In these respects, the present proposal can be considered as a simple empirical unified approach for rapid assessment of the notch effect under finite life.     

How accurately does the public perceive differences in transport risks?: An exploratory analysis of scales representing perceived risk

This paper probes the extent to which the public accurately perceives differences in transport risks. The paper is based on a survey of a random sample of the Norwegian population, conducted in September 2003. In the survey, respondents were asked: “How safe do you think it is to travel by means of (bus, train, etc.)?” Answers were given as: very safe, safe, a little unsafe, and very unsafe. A cursory examination of the answers suggested that the Norwegian public was quite well informed about differences in the risk of accident between different modes of transport, as well as between groups formed according to age and gender for each mode of transport. This paper probes the relationship between statistical estimates of risk and summary representations of perceived risk more systematically. It is found that the differences in fatality rate between different modes of transport are quite well perceived by the Norwegian public, irrespective of the way in which perceived risk is represented numerically. The relationship between statistical estimates of risk and numerical representations of perceived risk for each mode of transport is more sensitive to the choice of a numerical representation of perceived risk. A scale in which the answer “very safe” is assigned the value of 0.01 and the answer “very unsafe” is assigned the value of 10 is found to perform quite well. When the perception of risk is represented numerically according to this scale, a positive correlation between statistically estimated risk and perceived risk is found in seven of the eight comparisons that were made to determine how well variation in accident rates according to age and gender for car occupants, car drivers, cyclists and pedestrians are perceived.     

Prioritizing and quantifying the risk of outstanding corrective actions

This paper presents methods for assessing the risk of outstanding corrective actions, and describes how the methods were applied at a nuclear power station. The methods are motivated by a current industry focus on risk-informed operation and a current NRC focus on risk-informed regulation. Application of the methods provides: (1) a risk-informed basis for establishing schedules and allocating resources to implement corrective actions; (2) a risk-informed basis for justifying continued operation until corrective actions are implemented.     

Cost effectiveness and the choice of ‘best environmental options’

‘Best’ environmental options can be identified by standard techniques of economic analysis. However, the concept of ‘best’ will depend on the nature of the damage avoided by the use of different control types, the secondary cross-media effects of using environmental control, and the costs of control.

Control cost estimation does present problems but these can be largely overcome. However, damage estimates have been notoriously difficult to generate. To overcome some of the intractible problems, an alternative approach is suggested which is less powerful but more operational.     

风险管理在瓶装气体安全生产中的应用

由于气瓶充装过程具有易燃、易爆的危险特性,因此在瓶装气体生产企业需要一种行之有效的系统安全管理方法,来对安全风险实施预测和控制,避免事故发生。武钢氧气公司将危险辩识、风险评价和风险控制的风险管理方法应用于瓶装气体的生产管理中,取得了较好的效果。简析武钢氧气公司瓶装气体生产的工艺特点和基本危害,以及安全生产方面存在的主要问题;介绍瓶装气体生产过程中的风险分析和评价,以及相应的风险防范策略。     

A framework for the establishment of organizational risk indicators

Organizational risk indicators are proposed as a tool for risk control during operation of offshore installations, as a complement to QRA-based indicators. An organizational factor framework is developed based on a review of existing organizational factor frameworks, research on safety performance indicators, and previous work on QRA-based indicators. The results comprise a qualitative organizational model, proposed organizational risk indicators, and a quantification methodology for assessing the impact of the organization on risk. The risk indicators, when validated, will aid in a frequent control of the risk in the periods between the updating of the quantitative risk assessments.     

A Comparison of the Migration of ‘Spiked’ and ‘Intrinsic’ Substances from Paper and Board into Raisins and into Tenax as a Food Simulant

Four samples of paper and board (P/B) of a type used for packaging dry foods were subjected to migration experiments using raisins and the polymeric powder Tenax as a food simulant. The P/B samples contained only low levels of diisopropylnaphthalene (DiPN) and diisobutyl phthalate (DiBP), and so, experiments were also conducted after spiking the P/B with added model substances. These were o‐xylene, acetophenone, dodecane, benzophenone, DiPN and DiBP. Migration experiments into raisins and Tenax were conducted for 10 days at 40°C. Migration levels depended strongly on the nature of the substance. Migration from spiked P/B samples was more extensive (as a percentage of that available) than migration of intrinsic migratable substances, and so, studying spiked samples tends to be conservative. It is considered likely that this is because of binding of substances, especially aromatics with pi‐electrons such as DiPN and DiBP, to active sites on the surface of P/B fibres, resulting in non‐linear absorption isotherms. However, further work would be needed to prove this conclusively. Considering the results overall and also that raisins packed in P/B can have a shelf life of up to 1 year at ambient temperatures, the test results using Tenax as a food simulant are considered to be appropriate without application of a correction factor. Copyright © 2014 John Wiley & Sons, Ltd.     

‘Expert information’ versus ‘expert opinions’. Another approach to the problem of eliciting/ combining/using expert knowledge in PRA

In the traditional approach to eliciting expert knowledge for use in risk assessment and decision analysis, the expert is asked for his opinion about, say, the numerical value of some unknown parameter λ. This opinion is then expressed as a point estimate, λ_i, or a probabilistic estimate, P_i(λ). Much attention and debate is then given, in the traditional approach, to methods of weighing and combining the opinions from the individual experts.The present paper advocates another approach in which we ask each expert, instead, for his body of evidence, E_i, relevant to the value of λ. In this way, the approach first arrives at a consensual body of evidence, E − {E_i}, and second, at a consensual curve p(λ|E) that expresses our knowledge about λ based on that body of evidence.The essential difference between this ‘expert information’ approach and the traditional ‘expert opinion’ approaches may be captured in the slogan: lsWeigh evidence, not experts!’     

Load combination analysis by ‘Directional simulation in the load space’

The reliability of structures subjected to multiple time-varying random loads is considered herein. It is well-known that the reliability of such systems may be evaluated by considering outcrossings of the load process vector out of a safe domain, and the contribution of individual loads to structural failure may be evaluated by considering outcrossings caused by combinations of one or more loads. In this paper the ‘Directional Simulation in the Load Space’ approach to reliability analysis is developed to consider explicitly outcrossings caused by all possible combinations of loads, during analysis of systems comprising stationary continuous Gaussian loads. To do this, the direction of the load process vector is ‘fixed’ at each point of outcrossing (to physically represent the particular combination of loads causing the outcrossing), and, by considering each possible load combination, all loads not causing an outcrossing are then held constant during radial integration (to model correctly that they do not contribute to each outcrossing). A numerical example demonstrating the validity of the proposed formulation is presented.     

The use of a basic safety investment model in a practical risk management context

We consider a basic model in economic safety analysis: a firm is willing to invest an amount x in safety measures to avoid an accident A, which in the case of occurrence, leads to a loss of size L. The probability of an accident is a function of x. The optimal value of x is determined by minimizing the expected costs. In the paper, we re-examine this model by adopting a practical risk/safety management perspective. We question how this model can be used for guiding the firm and regulators in determining the proper level of investment in safety. Attention is given to issues like how to determine the probability of an accident and how to take into account uncertainties that extend beyond the expected value. It is concluded that the model, with suitable extensions and if properly implemented, provides a valuable decision support tool. By focusing on investment levels and stimulating thereby the generation of alternative risk-reducing measures, the model is considered particularly useful in risk reduction (ALARP) processes.