Abstract
While the consideration of human factors in the railway feedback of experience (REX) process is becoming a new priority, the procedures are far from systematic, and the methodologies remain uncertain. Inspired in particular by the works of Reason and Rasmussen and supported by application examples from the field of railway safety, the human error analysis approach proposed to improve the level of safety of rail transport systems involves three complementary levels. Before the accident, the first level of “contextual analysis” makes it possible to study the various factors favouring the production of the human error at the origin of the accident. During the accident and in the face of a critical situation, the second level of “cognitive analysis” focuses on finding and examining the human errors involved in the human cognitive process. Finally, after the accident, the last level of “behavioural analysis” focuses on the evaluation of the consequences and damage caused to humans, to the system, and to their environment.
TopIntroduction
The European directives and in particular the two 2016 directives on safety and interoperability require the creation, in each Member State, of a national safety authority led by the European Union Agency for Railways (ERA) and a permanent, specialized and independent investigative body, the equivalent of the BEA air (Land transport accident investigation bureau - BEA-TT). The aim is to create an integrated European railway area to harmonize the regulatory structure of the Member States, to develop common safety objectives and indicators and to put in place a safety management system, including the experience feedback (REX). The adverse consequences and the considerable cost of accidents due to the human factor, the occurrence of new disasters despite the progress of technology, are at the basis of the establishment of a system of REX as being the an essential means of promoting the necessary improvement of safety. Indeed, with the increasing complexity of industrial systems and especially guided or automated rail transport systems, considerable evolutions have taken place in the way of thinking and understanding the role and place of man in the safety of human-machine systems. In this context, human factors play an important role in safety analyzes and especially after the occurrence of accidents (feedback of experience) that sometimes lead to human losses and the destruction of the environment and system equipment. It is therefore necessary to implement a process of REX to memorize and capitalize all accidents and incidents and therefore avoid at least the reproduction of new accidents similar. The main purpose of the REX is to analyze the circumstances leading to the realization of unintended adverse events. It is a dynamic process of collecting, storing, analyzing and using data related to unhealthy situations. Its purpose is to take advantage of the lessons learned to improve the level of safety by implementing the appropriate preventive and corrective measures to avoid the reproduction of such a risk-bearing situation. In the majority of sectors and in particular the rail transport sector, the REX faces several obstacles and in particular the formal and systematic failure to take into account human factors in the analysis and evaluation of surveys following an accident such as a collision or derailment of a rail transportation system. The REX and generally limited to a purely technical dimension and yet, in almost all high-risk sectors, statistics show that human error is the basis in 70 to 80% of cases of accidents or incidents. Indeed, several studies emphasize that the obstacles to REX are multiple, the most important of which are the cross-cutting problems of the organizations of the company and the problems related to the analysis of human factors. The REX is much less efficient and much more limited when it deals with the human factor aspect and operational events directly or indirectly involving human intervention.
Key Terms in this Chapter
Accident Scenario: An accident scenario describes a combination of circumstances which can lead to an undesirable or even dangerous situation. It is characterized by a context and a set of events and parameters. An accident scenario is an adequate and orderly succession of events that may be the source of a potential accident risk (collision, derailment, electrocution, etc.). Each risk of accident likely to endanger the safety of travellers or to impair the ability of the system to perform the required safety functions is translated by safety experts into an accident scenario. The development of an accident scenario is based in particular on the history of transport systems already certified.
Human Error: The notion of human error is a very broad concept because it has multiple dimensions. Currently, there is no “common standard” for defining human error. Indeed, the term human error covers several meanings depending on the angle from which it is viewed. The diversity of points of view is linked to the multiplicity of disciplines which analyze it (psychology, ergonomics, engineering, sociology, philosophy, legal). It is an inappropriate (or involuntary) act of a human operator that generates a result not in accordance with what is expected (or desired). Human error is contrary to the notion of “Violation” which is defined by a voluntary deviation from the standard or recommendation. Rather, it is the consequences of a set of parameters external to the task at hand. Human error is an unwanted event, a sign of a mismatch, a lack of compatibility between the characteristics of the work situation, and the physical and mental characteristics of the human operator. Error is therefore an indicator or symptom of human activity. It results in an inappropriate an action on the system, action which will not succeed in making the results conform to the desired goal. Human error is not reducible to human inability or incompetence to perform a task, but can result from the inability of an operator to perform a task correctly. Human error depends, in large part, on the characteristics of the task (physical, technical, organizational, etc.). Human error cannot be defined without referring to human intention, as it depends on human judgment in a specific situation.
Vigilance, Attention, and Performance: Etymologically, the term vigilance means awakening. However, depending on the scientific disciplines (Neurophysiology, Neurology, Psychology, Philosophy, Medicine, Ergonomics, etc.), it evokes careful monitoring, the attention of an individual and his ability to perform a particular task, the waking state, etc. The concept of vigilance includes two aspects, a physiological one which corresponds to the level of arousal of the nervous system and a psychological one defined by attention. Attention is a concept associated with alertness that reflects a concentration of the level of perceptual, mental and motor activity. Vigilance then appears as a necessary but not sufficient condition for the mechanism of attention. Attention, which is generally interpreted in terms of efficiency or performance, represents an important psychological skill requiring well-defined levels of vigilance. Researchers have established a relationship between alertness and performance represented by an inverted U-curve model. The level of performance increases with that of vigilance to an optimum beyond which performance decreases with increasing level of vigilance.
Safety: The European standard CENELEC 50129 defines safety as “the absence of any unacceptable level of risk”. The probability of occurrence of a potential accident as well as the severity of the damage caused by this potential accident are the two components that identify the notion of risk. Therefore, to define the level of probability of a potential accident, the CENELEC 50126 standard proposes a set of categories, each of which is associated with a frequency range. Given the difficulty of estimating these frequencies, this quantitative / qualitative association is favorable. Likewise, the CENELEC 50126 standard defines the level of severity by associating the quantifications with the consequences generated by the potential accident. Indeed, the level of risk acceptability is identified and assessed using the “Occurrence / Severity” Matrix.
Investigation After Accident or Incident: After an accident or incident on the rail system, each Member State shall ensure that the investigations are carried out by a permanent body independent of any infrastructure manager, railway undertaking or national safety authority. Each accident or incident investigation must be documented in a report indicating the objective of the investigation and recommendations for safety. Each year, the investigative body must publish an annual report on the investigations carried out in the previous year, the recommendations made and the measures taken as a result of these recommendations.
Human Reliability Analysis: Human reliability can be defined from several angles. As a scientific discipline, it means the study of human failures which views man as a fallible agent. It can then be used to assess the influences of human error on safety and productivity. In terms of human quality, it is defined, by analogy with technical reliability, to designate the ability of an individual to perform, successfully or without error, a set of functions required under given conditions and for a given time.
Safety Principles: In Europe and in the rail transport sector, there are three main principles of safety. In Germany, we apply the MEM principle (Minimum Endogenous Mortality) which claims that we continue to improve the level of safety if only if the mortality rate due to technological events (exogenous to the organism) is lower than the endogenous mortality rate (in a specific place and space of time). In the United Kingdom, the principle is more economic. Indeed, the ALARP principle (As Low As Reasonably Practicable) applied there requires that a level of risk is acceptable if the cost due to the risk reduction is disproportionate compared to the improvement gain. In France, the GAME principle (Globally At Least Equivalent) is used. This principle stipulates that the level of security of a new system must be at least equivalent to that of a comparable system already in existence and deemed to be safe.
Feedback of Experience (Rex): The Rex corresponds to a thorough examination of the circumstances leading to the occurrence of events contrary to security. This is an approach that aims to highlight the shortcomings, dysfunctions and incompatibilities of the safety system and to formulate proposals likely to avoid such situations or reduce their consequences. This is not only to learn lessons to define effective short-term corrective security measures, but also to capitalize and develop knowledge of human and material behaviour in the medium term. Feedback corresponds to a dynamic process of collecting, storing, analyzing and exploiting data relating to situations contrary to safety (accident or incident). This is a causal analytical study of the various factors involved in the genesis of incidents or accidents. Feedback allows for a better understanding of the mechanisms leading to insecurity events. Its aim is to take advantage of the lessons of past experience to improve the level of safety by implementing the appropriate preventive and corrective measures in order to avoid the reproduction of such risky scenarios.
Risk Level: Since safety is generally defined as “the absence of any unacceptable level of risk”, it is therefore important to determine the “Level of Risk”. The latter requires two dimensions: 1) the Level of Probability of Occurrence of the potential accident and 2) the Level of Severity of the Damage caused by this accident. In practice, to assess safety and therefore the level of risk, the “Occurrence / Severity” Matrix is generally used, which jointly takes into account the two previous levels (Probability and Severity). Standard EN 50126 identifies 4 levels of risk: 1) Intolerable risks (must be eliminated), 2) Undesirable risks (cannot be accepted), 3) Tolerable risks (acceptable and with appropriate precautions) and 4) Negligible risks (acceptable, with the agreement of the safety manager).