Through industrialization, workers became organized in factories as the utilization of energy sources such as the steam engine became possible. As compared to traditional handicraft, mechanized production, with sources of higher energy at its disposal, presented new risks of accidents. As the amount of energy increased, workers were removed from the direct control of these energies. Decisions that affected safety were often made at the management level rather than by those directly exposed to these risks. At this stage of industrialization, the need for safety management became evident.
In the late 1920s, Heinrich formulated the first comprehensive theoretical framework for safety management, which was that safety should be sought through management decisions based on identification and analysis of accident causes. At this point in the development of safety management, accidents were attributed to failures at the worker-machine system level - that is, to unsafe acts and unsafe conditions.
Subsequently, various methodologies were developed for the identification and assessment of accident risks. With MORT (Management Oversight and Risk Tree), the focus shifted to the higher orders of control of accident risks - that is, to the control of conditions at the management level. The initiative to develop MORT was taken in the late 1960s by the US Energy Research and Development Administration, which wanted to improve their safety programmes in order to reduce their losses due to accidents.
The MORT Diagram and Underlying Principles
The intent of MORT was to formulate an ideal safety management system based on a synthesis of the best safety programme elements and safety management techniques then available. As the principles underlying the MORT initiative were applied to the contemporary state of the art in safety management, the largely unstructured safety literature and expertise took on the form of an analytical tree. The first version of the tree was published in 1971. Figure 1 shows the basic elements of the version of the tree that was published by Johnson in 1980. The tree also appears in a modified form in later publications on the subject of the MORT concept (see, for example, Knox and Eicher 1992).
The MORT Diagram
MORT is used as a practical tool in accident investigations and in evaluations of existing safety programmes. The top event of the tree in figure 1 (Johnson 1980) represents the losses (experienced or potential) due to an accident. Below this top event are three main branches: specific oversights and omissions (S), management oversights and omissions (M) and assumed risks (R). The R-branch consists of assumed risks, which are events and conditions that are known to management and that have been evaluated and accepted at the proper management level. Other events and conditions that are revealed through the evaluations following the S- and M-branches are denoted “less than adequate” (LTA).
The S-branch focuses on the events and conditions of the actual or potential occurrence. (In general, time is shown as one reads from left to right, and the sequence of causes is shown as one reads from bottom to top.) Haddon’s strategies (1980) for the prevention of accidents are key elements in this branch. An event is denoted an accident when a target (a person or object) is exposed to an uncontrolled transfer of energy and sustains damage. In the S-branch of MORT, accidents are prevented through barriers. There are three basic types of barriers: (1) barriers that surround and confine the energy source (the hazard), (2) barriers that protect the target and (3) barriers that separate the hazard and the target physically or in time or space. These different types of barriers are found in the development of the branches below the accidental event. Amelioration relates to the actions taken after the accident to limit the losses.
At the next level of the S-branch, factors are recognized which relate to the different phases of the life cycle of an industrial system. These are the project phase (design and plan), start up (operational readiness) and operation (supervision and maintenance).
The M-branch supports a process in which specific findings from an accident investigation or safety programme evaluation are made more general. Events and conditions of the S-branch thus often have their counterparts in the M-branch. When engaged with the system at the M-branch, the analyst’s thinking is expanded to the total management system. Thus, any recommendations will affect many other possible accident scenarios as well. The most important safety management functions can be found in the M-branch: the setting of policy, implementation and follow-up. These are the same basic elements that we find in the quality assurance principles of the ISO 9000 series published by the International Organization for Standardization (ISO).
When the branches of the MORT diagram are elaborated in detail, there are elements from such different fields as risk analysis, human factors analysis, safety information systems and organizational analysis. In total, about 1,500 basic events are covered by the MORT diagram.
Application of the MORT Diagram
As indicated, the MORT diagram has two immediate uses (Knox and Eicher 1992): (1) to analyse management and organizational factors relative to an accident that has happened and (2) to evaluate or audit a safety programme in relation to a significant accident that has the potential of occurring. The MORT diagram functions as a screening tool in planning the analyses and evaluations. It is also used as a checklist for comparison of actual conditions with the idealized system. In this application, MORT facilitates checking the completeness of the analysis and avoiding personal biases.
At bottom, MORT is made up of a collection of questions. Criteria that guide judgements as to whether specific events and conditions are satisfactory or less than adequate are derived from these questions. In spite of the directive design of the questions, the judgements made by the analyst are partly subjective. It has thus become important to ensure an adequate quality and degree of intersubjectivity among MORT analyses made by different analysts. For example, in the United States, a training programme is available for certification of MORT analysts.
Experiences with MORT
The literature on evaluations of MORT is sparse. Johnson reports significant improvements in the comprehensiveness of accident investigations after the introduction of MORT (Johnson 1980). Deficiencies at the supervisory and management levels were revealed more systematically. Experience has also been gained from evaluations of MORT applications within Finnish industry (Ruuhilehto 1993). Some limitations have been identified in the Finnish studies. MORT does not support the identification of immediate risks due to failures and disturbances. Furthermore, no capability for setting priorities is built into the MORT concept. Consequently, the results of MORT analyses need further evaluation to translate them into remedial actions. Finally, experience shows that MORT is time-consuming and requires expert participation.
Aside from its ability to focus on organizational and management factors, MORT has the further advantage of connecting safety with normal production activities and general management. The application of MORT will thus support general planning and control, and help reduce the frequency of production disturbances as well.
Associated Safety Management Methods and Techniques
With the introduction of the MORT concept in the early 1970s, a development programme started in the United States. The focal point for this programme has been the System Safety Development Center in Idaho Falls. Different MORT-associated methods and techniques in such areas as human factors analysis, safety information systems and safety analysis have resulted from this programme. An early example of a method arising from the MORT development programme is the Operational Readiness Program (Nertney 1975). This programme is introduced during the development of new industrial systems and modifications of existing ones. The aim is to ensure that, from the safety management point of view, the new or modified system is ready at the time of start-up. A condition of operational readiness presupposes that the necessary barriers and controls have been installed in the new system’s hardware, personnel and procedures. Another example of a MORT programme element is the MORT-based root cause analysis (Cornelison 1989). It is used to identify the basic safety management problems of an organization. This is done by relating the specific findings of the MORT analyses to 27 different generic safety management problems.
Although MORT is not intended for use directly in the collection of information during accident investigations and safety audits, in Scandinavia, the MORT questions have served as a basis for the development of a diagnostic tool used for this purpose. It is called the Safety Management and Organization Review Technique, or SMORT (Kjellén and Tinmannsvik 1989). A SMORT analysis advances backwards in steps, starting from the specific situation and ending at the general management level. The starting point (level 1) is an accident sequence or a risk situation. At level 2, the organization, system planning and technical factors related to daily operation are scrutinized. The subsequent levels include design of new systems (level 3) and higher management functions (level 4). Findings on one level are extended to the levels above. For example, results related to the accident sequence and to daily operations are used in the analysis of the company’s organization and routines for project work (level 3). Results at level 3 will not affect safety in existing operations but may be applied to the planning of new systems and modifications. SMORT also differs from MORT in the way findings are identified. At level 1, these are observable events and conditions that deviate from generally accepted norms. When organizational and management factors are brought into the analysis at levels 2 to 4, the findings are identified through value judgements made by an analysis group and verified through a quality control procedure. The aim is to ensure a mutually shared understanding of the organizational problems.
MORT has been instrumental in developments within safety management since the 1970s. It is possible to track the influence of MORT to such areas as safety research literature, literature on safety management and audit tools, and legislation on self-regulation and internal control. In spite of this impact, its limitations must be carefully considered. MORT and associated methods are normative in the sense that they prescribe how safety management programmes should be organized and executed. The ideal is a well-structured organization with clear and realistic goals and well-defined lines of responsibility and authority. MORT is thus best suited for large and bureaucratic organizations.