COMMENT ON HUMAN RELIABILITY IN SHIP-HANDLING IN RESTRICTED WATERS

Danilo Taverna Martins Pereira de Abreu Marcos Coelho Maturana

Marcelo Ramos Martins

Affiliates to the Laboratory of Risk Analysis, Assessment and Management (LabRisco) of University Sao Paulo (USP)

How much does a ship accident in restricted waters cost? The stranding of the ship Ever Given in the Suez Canal in 2021 showed the world that the consequences are significant and not limited to the vessel. The losses directly affect the users of an access canal and, indirectly, extend to society as a whole, that depends on sea transportation for the smooth running of international trade and supply chains. Nevertheless, depending on the characteristics of the accident, fatalities and environmental damages of major impact could occur.

In a scenario with accidents that could exceed millions of dollars, it is essential to understand the potential causes of hazardous events and act preventively. In the context of navigation in restricted waters, pilotage works to this end, to provide the waterway traffic with high security. The port environment, however, is a complex sociotechnical system; in other words, it involves interactions between humans and physical structures (e.g., the navigation canal and ships) that cannot be fully understood so easily. In this uncertain environment, despite the excellence of the navigators and other stakeholders, accidents might occur by combining factors otherwise regarded as of little importance.

Professionals, researchers and representatives of regulatory agencies – such as nuclear, aviation, maritime and processing industries – have spent years seeking to understand the dynamics of complex sociotechnical systems in order to mitigate their risks. Around twenty years ago, it was common to attribute the majority of accidents to “human error”. Although the concept is still used technically, there has been significant development in relation to its meaning. Currently, it is understood that accident-prone human actions cannot be separated from the context in which the professionals are, and that the influencing factors must be taken into account in more in-depth analyses.

The human reliability analysis (HRA) is the field dedicated to understanding how humans can contribute to the occurrence of accidents and to investigating the main influencing factors, in order to provide insight in risk-based decision making. In partnership with the National Pilotage Council, LabRisco has developed a research project to prepare HRA in typical navigation operations in restricted waters, to understand factors that may influence the pilots’ and navigators’ performance, and to assess the contribution of the pilot’s work in reducing risks.

The work method was based on the modelling of human actions and contributing factors based on the use of Bayesian networks. This type of model originated in the field of artificial intelligence and helps consider relations of dependence between random variables. In practice, this helps identify how different factors that influence an operation act together to contribute to deviations and errors that could result in accidents.

In the study, four types of factors were considered, in accordance with the generic model of dependence shown in Figure 1. This model resumes that human actions are influenced by the operator’s skills. In turn, the skills are influenced by internal factors of the operator and environmental factors. These internal factors, in turn, are influenced by management and organizational factors (referred to as Management & Organizational Factors - MOFs).

The work method is divided into four stages:

1) Familiarization: in which the researchers watch real maneuvers and simulations, and interview professionals in the field (pilots, ship captains, nautical officers and tug captains).

2) Qualitative analysis: based on findings from the familiarization stage, the researchers developed a Bayesian network in which nodes represent relevant human actions and factors that influence performance, and the arcs (arrows) indicate the dependency relations – see Figure 2 for didactic illustration. This stage also involved modelling sequences of actions for three accident scenarios: collision and stranding while navigating the canal and collision when approaching a terminal.

3) Quantitative analysis : from databases in literature, the probabilities of error in each human action was estimated and the Bayesian network calibrated, in order to qualify the weight of the charted influences.

4) Incorporation: in this last stage the Bayesian network results were generated, including the estimation of the probability of human error in typical accidents, considering the use of no pilot, one or two pilots onboard; a sensitivity analysis was also carried out to understand which factors have more influence on the error probability.

The technical details of applying the methodology were published in the scientific journal Reliability Engineering and System Safety 1 In short, for each accident scenario, the main actions taken by the professionals involved in navigation were modeled. Table 1 provides the activity categories considered in each scenario and the professional in charge. For analysis purposes, the ship’s qualified captain was considered to act in the event of pilotage exemption.

Before the quantitative analysis, it is already possible to note some differences between the various team configurations. In relation to the scenario with one pilot onboard, the presence of a second pilot onboard offers redundancy for the maneuver supervision stage. However, the scenario with exempt pilotage loses the redundancy in this regard. The effect of this impact on the probability of human error was estimated from quantifying the model. In terms of factors that modify the performance, Table 2 indicates the elements considered in each category. The MOFs were considered for the following organizations whenever applicable: local pilotage, shipowner and tug operator.

The first set of results of the study consists of comparing the accident probabilities in the different scenarios considered. Table 3 presents the values obtained. These probabilities refer to the possibility of an accident happening given the existence of a scenery of an accident (e.g., a ship sailing dangerously by another vessel while navigating the canal). The figures must not, therefore, be interpreted absolutely or separately. Allowing for a pilot onboard as reference, the job of the second pilot can reduce to around 3.5 times the probability of an accident happening. However, in the case of pilotage exemption, when compared to one pilot onboard, it increases to around seven times the probability of an accident.

Another interesting result of the study involved the evaluation of the factors that most influence performance during ship handling. This is a complex sensitivity analysis that can be consulted in detail in the scientific publication, since all factors in all combinations of scenarios have been taken into consideration. Along general lines, however, it is worth mentioning the following factors: a) Familiarity skill with the situation: many tasks involved in shipping in restricted waters have their performance influenced by local experience. Familiarity skills with the situation reflect this expertise, and its state has significant influence on the probability of error in more important actions. b) Teamwork skills: irrespective of the bridge team configuration, shipping activities in restricted waters require ongoing interaction between the stakeholders. Communication problems (e.g., pilot vs. helmsman, pilot vs. tug captains) or supervision (e.g., ship captain vs. pilot, first vs. second pilot) have a strong impact on the maneuvering performance. c) Internal training and experience factor: as a result of the importance of familiarity with the situation, training and experience ship handling is a factor that is important in the analysis, since it incorporates the knowledge acquired by repetition of daily tasks, as well as the effect of training activities that prepare the seafarer for routine or unprecedented situations. d) Safety culture MOF: the concept of safety culture refers to the way in which organizations prioritize and implement actions in favor of preventing events that may be harmful to people, the environment and heritage. Regardless of the organization in question, the performance in accident-prevention actions is influenced by how the organization regards this factor.

In short, the developed research project advanced toward helping understand how the human factor might influence the risk of ship handling in restricted waters. This is a first approach to understanding the impact of the configurations of a navigation team (with one or two pilots onboard or pilotage exemption). However, there are still a number of issues to clarify through future work, such as how the ship leaves a safe status and finds itself in a hazardous situation or the application of the model developed in specific case studies of a port or inland waterways.

Internal factors

Management & organizational factors

Skills

Environmental factors

Human actions

Internal factors nodes

Skills nodes

Human actions nodes

MOFs nodes

Environmental factors nodes

Accident scenario

One pilot onboard

• Pilot: monitoring, interpreting situation, request for situation, request to execute commands

• Ship’s captain: monitoring, interpreting situation, supervision

• Helmsman: obeying orders

• Pilot: monitoring, interpreting situation, request to execute commands

• Ship’s captain: monitoring, interpreting situation, supervision

• Helmsman: obeying orders

• Pilot: monitoring, interpreting situation, request to execute commands

• Ship’s captain: monitoring, interpreting situation, supervision

• Helmsman: obeying orders

• Tug captains: obeying orders

Team Configuration

Two pilots onboard

• Pilot: monitoring, interpreting situation, request to execute commands

• Second pilot: monitoring, interpreting situation, supervision

• Ship’s captain: monitoring, interpreting situation, supervision

• Helmsman: obeying orders

• Pilot: monitoring, interpreting situation, request to execute commands

• Second pilot: monitoring, interpreting situation, supervision

• Ship’s captain: monitoring, interpreting situation, supervision

• Helmsman: obeying orders

• Pilot: monitoring, interpreting situation, request to execute commands

• Second pilot: monitoring, interpreting situation, supervision

• Ship’s captain: monitoring, interpreting situation, supervision

• Helmsman: obeying orders

• Tug captains: obeying orders

Pilotage exemption

• Ship’s captain: monitoring, interpreting situation, request to execute commands

• Helmsman: obeying orders

• Ship’s captain: monitoring, interpreting situation, request to execute commands

• Helmsman: obeying orders

• Ship’s captain: monitoring, interpreting situation, request to execute commands

• Helmsman: obeying orders

• Tug captains: obeying orders

MOFs

• Activity management

• Personnel management

• Safety culture

• Job satisfaction

• Availability of information

• Suitability of jobsite

• Business pressure

• Training

• Job standardization

Environmental factors

• Visual conditions

• Climate conditions

• Work environment quality

• Factors hazardous to shipping

Internal factors

• Physical status

• Mental state

• Perceived situation

• Attitude

• Training & experience

• Identifying with team

• Time pressure

Skills

• Assessment of situation

• Awareness of situation

• Familiarity

• Physical skills

• Teamwork

• Response

• Vision