The Impact of Regulation Amendments on Decision Support System Effectiveness on the Example of Vessel Traffic Planning on the Dredged Świnoujście–Szczecin Fairway

Abstract

Detailed planning of vessel traffic on the fairway, carried out by Vessel Traffic Service (VTS) operators, is a complicated task, especially when there are restrictions for two-way ship traffic. Such restrictions take place on the dredged Świnoujście–Szczecin fairway in Poland. After the dredging of the fairway to 12.5 m, vessel traffic regulations introduced in a Port Regulations document have changed, which impacted the course of the decision-making process related to planning vessel traffic on the fairway performed by VTS operators. The aim of the article is to assess the probability of making erroneous decisions related to the admission of non-compliant vessels to traffic on the dredged Świnoujście–Szczecin fairway after the introduction of new vessel traffic regulations. In the article, the tasks carried out by VTS operators during vessel traffic planning were described and analyzed using Failure Mode and Effects Analysis (FMEA) method. The probability of making an erroneous decision at each stage of the planning process was calculated using the Human Error Assessment and Reduction Technique (HEART) method. An event tree was developed in relation to VTS operators’ decision-making on vessel traffic planning performed before and after the introduction of a decision support system (DSS). An expert method was used to determine the probability values. Recommendations were proposed to reduce the risk of making erroneous decisions by VTS operators while vessel traffic planning. The research results contributed to the expansion of knowledge on the impact of new regulation implementation on vessel traffic safety and the risk of making erroneous decisions related to the admission of non-compliant vessels to traffic on the dredged Świnoujście–Szczecin fairway, considering the implementation of a DSS. The results of the study may be of interest to VTS operators, port authorities and maritime administrations.

1. Introduction

Vessel traffic safety plays a key role in maritime transport [1]. Different factors may affect vessels during the voyage, especially while moving through the fairways and the port areas [2,3]. Therefore, the International Maritime Organization (IMO) introduces rules and regulations aimed at improving the safety of shipping and protecting the marine environment [4]. An important role in implementing these tasks has been assigned to Vessel Traffic Service (VTS) systems. Such types of systems have also been established in Poland [5].

VTS operators plan and organize vessel traffic in designated areas, as well as cooperate with the ships’ masters when the vessels call at port. When entering or leaving ports, vessels should comply with specific regulations related to safe operation in dedicated waters (such as narrow passages, fairways and port basins, etc.) due to complex navigation conditions. Weather conditions, limitations of ships’ dimensions and rules for passing ships on waterways, etc., are usually described in these regulations [6,7,8].

Vessel traffic planning is a key element of the “Traffic Organization Service” offered by the VTS systems [9]. Vessel traffic planning is necessary, especially when there are restrictions on two-way traffic on a fairway, in areas where there are locks, determined passing areas for ships or there is tanker traffic [9]. The decision to allow a ship to enter traffic is made by the VTS operator. An error in the VTS operator’s decision may result in a non-compliant ship being allowed to enter the fairway, i.e., that may pose a potential threat to maritime traffic and introduce the risk of vessel collision or grounding.

The Świnoujście–Szczecin fairway was dredged to 12.5 m, which allows larger vessels to enter ports in Świnoujście, Szczecin and Police [10,11]. The fairway was opened for larger vessels in April 2023 and caused challenges for decision-making process performed by VTS operators. The commissioning of a fairway before the introduction of new traffic rules was to deal with the higher risk of making erroneous decisions by VTS operator.

Analysis conducted on the available literature revealed that a lot of attention is paid to the issues of safe and reliable operation of maritime transport [12]. Risk assessment has become an important activity for area-based marine management [13]. Decision support systems (DSSs) are introduced to reduce and manage risks. In the reviewed studies, the risk of vessel traffic on the Świnoujście–Szczecin fairway was considered [14,15,16]. However, the issues of decision-making processes related vessel traffic planning on the Świnoujście–Szczecin fairway in regard to introduction of amendments in regulations on vessel traffic contained in Port Regulations [17] were analyzed to a limited extent.

The aim of the study was to assess the probability of making erroneous decisions related to the admission of non-compliant vessels to traffic on the dredged Świnoujście–Szczecin fairway after the introduction of new vessel traffic regulations. The Failure Mode and Effects Analysis (FMEA) form was established and the Human Error Assessment and Reduction Technique (HEART) method was used. Event trees were developed in relation to VTS operators’ decision-making on vessel traffic planning before and after the implementation of a DSS that includes the implementation of decision support tool (“calculator”) and training was carried out for VTS operators.

The article includes Section 2, where the results of the literature analysis are shown. In Section 3 the research methodology is performed. Results of the considerations carried out are presented in Section 4. In order to sum up the conclusions drawn, a discussion was carried out and recommendations for VTS operators to reduce the risk level of failure in the decision-making process while vessel traffic planning were proposed.

2. Literature Review

2.1. Characteristics of the Świnoujście–Szczecin Fairway and Decision-Making Process for Vessel Traffic Planning

The need to plan and organize vessel traffic on the Świnoujście–Szczecin fairway using a VTS system results from technical limitations of the fairway (its width and technical depth) [18]. The main task of the VTS Świnoujście–Szczecin system, implemented on the fairway in 2000, was, among other things, to ensure two-way vessel traffic, achieve the assumed capacity and ensure the safety of vessels calling at the ports of Świnoujście, Szczecin and Police. Two centers (VTS Center Szczecin and VTS Center Świnoujście) are involved in this process. For about two decades, vessel safety and traffic planning were ensured in accordance with rules introduced in 2000. According to these rules, the combined length, width and draught of passing vessels was considered to plan the traffic. These rules resulted from the ship traffic organization system that was operated by the Maritime Office in Szczecin before 2000 and was modified over the years. Applied rules were based on guidelines introduced by the PIANC (Permanent International Association of Navigation Congresses–The World Association for Waterborne Transport Infrastructure) [19].

Implementation of the project related to the dredging of the Świnoujście–Szczecin fairway to 12.5 m [10] in 2020–2022 impacted the need to change the current approach to plan vessel traffic and establish the new rules for the safe operation of ships on the dredged fairway. The principles for the new traffic organization on the particular sections of dredged fairway were elaborated [14]. These principles were related to establishment of two passing areas “Mijanka Zalew” and “Mijanka Police” within the fairway. Considering that after dredging, the fairway had different parameters than before, it was necessary to provide amendments to the rules for vessel traffic planning on the entire fairway, i.e., a DSS had to be developed (Figure 1).

As a new approach for vessel traffic management, a set of parameters (including ship length overall, width, draft and channel slope at a given location) was used to determine vessels’ compliance groups. The PIANC standards [19] also refer to the possibility of this solution’s implementation. Ships that enter the Świnoujście–Szczecin fairway were divided into compliance groups depending on their length, width and draught. Moreover, the rules for vessels passing each other in particular sections of fairway were determined. Dimensions of vessels that may enter the Świnoujście–Szczecin fairway introduced in Port Regulations adopted 6 April 2023 [17] are presented in

Table 1. Particular compliance groups of vessel dimensions that may enter the Świnoujście–Szczecin fairway introduced in the Port Regulations (as of 06 April 2023) [17].

Group	LOA * [m] ≤	B * [m] ≤	T * [m] ≤
0	Auxiliary port vessels, bunker vessels supplying ships with fuel, inland navigation passenger vessels, barges and push boats with single-section barges.
1	100	15	4
2	120	20	6
3	160	25	8
4	200	30	11
5	240	32.3	11

* LOA—length overall, B—width, T—draught.

. The rules for passing the ships assigned to particular compliance groups within specific sections of the fairway are shown in

Table 2. Passing rules of different compliance groups’ vessels in particular sections of the Świnoujście–Szczecin fairway introduced in the Port Regulations (as of 06 April 2023) [17].

No.	Section of Fairway	Fairway Mileage (km)	Type/Shape of Fairway	Rules of Mutual Passing of Compliance Groups Vessels
1.	Mielin N-Paprotno	5.40–11.4	Bend	0 **, 1/1, 1/2, 1/3, 2/2, 2/3
2.	Kanał Piastowski	11.4–17.0	Straight	0 **, 1/1, 1/2, 1/3, 2/2, 2/3, 3/3
3.	Zalew N	17.0–23.8	Straight	0 **, 1/1, 1/2, 1/3, 1/4, 1/5 2/2, 2/3, 3/3
4.	Mijanka Zalew II BT–III BT	23.8–28.8	Passing area	0 **,1/2/3/4/5 *
5.	Zalew S	28.8–41.0	Straight	0 **, 1/1, 1/2, 1/3, 1/4, 1/5, 2/2, 2/3, 3/3
6.	Mieszany N	41.0–49.5	Bend/straight	0 **, 1/1, 1/2, 1/3, 2/2, 2/3, 3/3
7.	Mijanka Police	49.5–51.5	Passing area	0, 1/2/3/4/ *
8.	Mijanka Police– Inoujście	51.5–54.0	Straight	0 **, 1/1, 1/2, 1/3, 2/2, 2/3, 3/3
9.	Inoujście– Orli Przesmyk	54.0–64.0	Bend/straight	0 **, 1/1, 1/2, 1/3, 2/2, 2/3
10.	Przekop Mieleński	64.0–67.0	Straight	0 **, 1/1, 1/2, 1/3 ***, 2/2

*—mutual passing of ships of all indicated size groups. **—mutual passing with ships of all size groups. ***—ships of size group 3 with maximum parameters up to length—160 m, width—25 m, draught—9.5 m.

.

Compliance groups 0–5 (Table 1) were included in the Port Regulations adopted 06 April 2023 [17] in order to address all possible vessel traffic within the fairway, including vessels such as auxiliary port vessels, bunker vessels supplying ships with fuel, inland navigation passenger vessels, barges and push boats with single-section barges. Each particular vessel has to be assigned to a specific compliance group. Consideration of these groups is necessary for VTS operators to make decisions on planning vessel traffic and allowing vessels to pass each other while crossing particular sections of the fairway. Moreover, the column “rules of mutual passing of compliance groups vessels” (Table 2) presents the permitted passing relationships between vessels assigned to specific compliance groups along the designated section of the fairway. Vessels assigned to groups 4 and 5 cannot pass other vessels while navigating a given section of fairway. In turn, vessels assigned to group 0 may meet the length-related criteria for vessels of group 1 or group 2; however, due to their specific maneuvering capabilities, design characteristics or other operational parameters, they have been exempted from the general one-way traffic restrictions. The inclusion vessels in group 0 was based on operational analyses and consultations with stakeholders, including pilots. These new regulations introduced changes in decision-making process carried out by VTS operators while planning vessel traffic within the fairway.

Considering that the previous vessel traffic planning rules were used by VTS operators for over twenty years, the risk of errors related to routine and other aspects associated with human factors was realistic. There were concerns that a human error may occur during designated processes, which could result in delays in planning, the need for replanning or, in the worst case, the introduction of a vessel into the fairway that does not comply with the established traffic rules.

When traffic planning rules are applied, the final approval for a vessel to join the traffic is based on a repetitive decision-making process [21], which is performed within several steps (considering the viewpoint of VTS operators working at the VTS Centre Szczecin) that are shown in Figure 2.

In the article, attention will be focused on Step 1 “Vessel traffic planning” at VTS Center Szczecin. This task includes the following sub-tasks:

1.1.

Commencement of the process for notified ships.

2.1.

Agreement of the vessels schedule with the port’s authority.

3.1.

Agreement of the vessel’s schedule with the VTS Center Świnoujście.

4.1.

Communication of the decision to the master of the vessel and pilot.

The described decision-making process is initiated by the VTS operator; particular decisions are agreed with subsequent decision-making participants. The process is based on an analysis of vessels scheduled to enter or leave the ports of Świnoujście, Szczecin or Police. Vessel traffic planning is carried out dynamically, as new requests and ship notifications are received. Due to the conditions of ship notifications, it can be assumed that in a 6 h cycle, the operator analyses the requests of four arriving ships and four departing ships. Then, the operator agrees the entry priority for individual vessels with the port’s authority (dispatcher). Based on the agreed vessel schedule, the operator consults the expected vessel traffic with the operator from VTS Centre Świnoujście. The agreed decisions on time periods when the vessels can enter the fairway are forwarded directly to the masters and pilots of the waiting ships. In the case of vessel schedule modifications (resulting from changes in vessel traffic within the Świnoujście port) the decision-making process is repeated.

2.2. Analysis of the Literature Related to Risk Assessment

The literature related to decision-making processes and associated risks is quite extensive. Risk is defined as the combination of the probability of an event and its consequences [22]. It was noted that risk seeking, inconsistent management and erroneous analytical tools can all contribute towards sub-optimal decision-making [23]. Kim and Lee [24] paid attention to the de-subjectivization of top decision makers, situational awareness, as well as the need to understand context of decision-making process and gather information relevant to take a decision. That also refers to rational decision-making process of vessel traffic planning performed by VTS operators.

In the available studies, attention is drawn to the need to take into account the specific conditions for vessel traffic on the route. For example, risks may appear while ships are crossing near specific infrastructure (e.g., Offshore Wind Farms) or moving within the port’s areas [25,26]. Dudchenko et al. [27] developed the approach that allows for the synthesization of an optimal route for the vessel, considering minimum fuel consumption and minimal accidents risk for the vessel and cargo, as well as variable operating conditions along the route.

During maritime transport operations, different risks may appear. It is essential to measure and analyze these risks [28]. Olba et al. [29] paid attention to the fact that the increase in port calls and cargo can impact port operations; therefore, it is essential to anticipate any future capacity drop or increase in nautical risks. A multi-criteria decision-making methodology allowing us to evaluate the trade-off between safety and capacity of vessel traffic in ports, considering other assessment indicators, was developed.

In the literature, the problem of human error in maritime safety management has been highlighted in several areas. One of them deals with human relations perceived as a source of potential conflicts which, consequently, affects the risk of decision-making errors [30]. It was noted that in studies on maritime accidents, human error is identified as the primary contributing cause for up to 70% of the accidents [31]. Fan et al. [32] also analyzed human factor impact on maritime accidents and proposed the methodology for a maritime accident prevention strategy formulation from a human factor perspective. This methodology incorporated a Bayesian network and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) in a multi-criteria decision-making system. The clear order, information and safety culture were considered to be essential for maritime accident prevention.

The distortion of information during its processing also may impact erroneous decision occurrences [33,34]. It was stated that depending on the distortion degree of the information possessed by managers, their decisions may be erroneous to a varying degree, the degree of managerial decisions’ incorrectness can be evaluated by the number of decision-making cycles (e.g., within the DSS) required to make and apply an effective decision.

The nature and role of potential conflicts leading to the emergence of threats were analyzed both in scientific studies and in documents issued by international organizations dealing with maritime safety [35,36]. Jiang at al. [37] examined the key risks of the influential factors of embarkation and disembarkation accidents of marine pilots. “Insufficient pilot ladder strength” was considered as the most critical among the analyzed factors.

Different measures, tools and methods to assess the risk have been proposed [36]. A risk assessment system for navigational obstacles considering collision and pollution risks was developed by Lee et al. [38]. Advancements of well-established approaches and new, promising tools in the risk assessment of ship collision, considering methods allowing for the consideration of quantitative and qualitative variables in the assessment were discussed by Marino et al. [39]. Goerlandt [13] presented a brief overview of risk analysis techniques promoted at the international level, and outlined selected approaches proposed in the academic literature.

Yıldız et al. [40] stated that human factor remains a leading cause of marine accidents, and there is no single approach universally chosen for use as the most effective. Therefore, they proposed a dynamic hybrid model based on the Human Factors Analysis and Classification System (HFACS) and Bayesian networks to foresee and assess accident risks in narrow waterways. Park et al. [41] used a random forest model based on historical collision data to establish external risk factors, while developing a comprehensive ship collision risk model. To improve the level of risk management in inland waterways for sustainable development, Ye et al. [42] proposed two-stage risk evaluation model that integrates a fuzzy rule base and Bayesian networks. They identified 19 risk sources and analyzed them from the perspectives of humans, ships, the environment and management. An enhanced Bayesian decision support model integrating the Leaky Noisy-MAX mechanism to consider uncertainties and complexities in ship accident risk analysis was elaborated by Xue et al. [43]. Causal chains that show the most likely pathways leading to accidents were revealed.

Shin and Yang [26] developed and evaluated machine learning models to predict maritime accidents, considering environmental and VTS features. Data applied from Busan Port, XGBoost, random forest, Neural Network and Support Vector Machine models were compared. Sui et al. [44] applied complex network theory and modeled the vessel traffic as a virtual network. They used real traffic data from Yangtze River to demonstrate the performance of the proposed method. This method may help VTS operators better understand the vessel traffic situation and to take control measures. Dhyani et al. [45] proposed a method based on a partially observable Markov decision process model allowing online risk mitigation of autonomous inland vessel.

In the literature there are also studies that include comparative analysis of risk assessment methods and techniques. An analysis of the Bow tie, Brainstorm, Check list, FMEA and HAZOP (Hazard and Operability Studies) methods and techniques was presented in [46], but the authors did not decide which of the techniques used was the best. A similar analysis of various techniques was carried out by Stojliljkoovic et al. [47], where the APJ (Absolute Probability Judgment) method was used to determine the probability of human error in the case study described. The calculations were performed in several areas classified as human errors. Purba et al. [48] used a Formal Safety Assessment (FSA) for ship collision risk analysis in the Surabaya West Access Channel. It is worth mentioning here that the HEART method [49] is commonly used to estimate the risk of human error in processes related to the operation of critical infrastructure [50,51] and NASA’s space industry [52].

The available literature also refers to the operation of modern waterways [53] including the Świnoujście–Szczecin fairway. Selected decision-making issues in vessel traffic planning after the dredging the Świnoujście–Szczecin fairway to 12.5 m were addressed [18]. Analysis of the safety of ship operation on the rebuilt waterway [14] was carried out and navigational risk based on AIS (Automatic Identification System) data in a context of specific investments (planned container terminal project in Świnoujście) was also analyzed [15]. The accessibility of the Świnoujście–Szczecin fairway for deep-draught ships was also analyzed [6]. The statistical model of ship delays on the Świnoujście–Szczecin fairway in terms of restrictions resulting from the Port Regulations was shown [16].

Moreover, it is essential to analyze data concerning the aspects of human element, the technical and administrative work related to specific conditions of VTS centers’ operation to ensure navigation safety [54]. The sources of threats resulting from human activity as a part of the VTS system were assessed [55]. Operators’ experience stands out as very influential factor impacting maritime safety [56]. Baldauf et al. [54] paid attention to the fact that training may significantly increase the skills and knowledge of VTS personnel. Therefore, VTS operators are usually trained to use measures dependent on the risk level of a certain situation’s occurrence [57].

Based on the conducted literature review it was stated that:

• The available studies reviewed mainly refer to risks occurring during vessel traffic within the route and do not take into account the decision-making process taken by VTS operators while planning the vessel’s entrance on fairways;
• The risks related to decisions carried out by VTS operators while planning vessel traffic on the Świnoujście–Szczecin fairway were analyzed to a limited extent;
• The probability of erroneous decisions during the planning of vessel traffic on the dredged Świnoujście–Szczecin fairway, considering the changes in vessels traffic regulations and the introduction of a DSS, should be analyzed in more detail.

In regard to the research problems described in the article, the authors decided to use the HEART [49,51] and FMEA [58,59] methods, as recommended in [50]. This choice was based on the nature of the operating environment under analysis, in which both technical processes and the human factor play a significant role. These methods were applied to analyze different aspects of maritime transport operation.

The HEART method makes it possible to assess the probability of decision-making errors performed by VTS operators, taking into account the impact of time pressure, stress, changing external decision-making conditions and incomplete data [60]. Maritime accident assessment and reduction techniques were considered to facilitate technical understanding of the risk and safety linked to human factors [61]. In the available literature, the HEART method was used to analyze grounding accidents [62] and determine the level of operator reliability [63], as well as to identify the major errors with mitigating actions taken after fire detection onboard passenger vessels [64]. Moreover, error-producing conditions in relation to a ship’s operational management were analyzed by applying the HEART method [65].

In turn, the FMEA method allows us to identify potential types of failures in the decision-making process and their consequences, which makes it possible to set a risk priority and identify the most critical areas of the process under analysis that require improvements. FMEA methodology is widely used to evaluate potential risks that may occur [66]. FMEA was used to analyze different problems and risks related to maritime transport operations, including handling operations in marine bulk terminals [67], ship berthing/unberthing operations [68], the casualty of the merchant vessels [69], the operation of icebreakers in ice-covered waters [70], maritime autonomous surface ships operation [71], ship collisions [72] and others. Failure modes and effects of intelligent ship positioning systems were analyzed by Luo et al. [73]. According to Alan and Bal Beşikçi, the integration of the FMEA method into VTS reporting processes resulted in a 45% methodological improvement [74].

Application of these two methods makes it possible to provide a hybrid framework addressing both the technical and the human reliability aspects impacting decision-making conducted by operators. Their combined application was tailored to meet the multifactorial nature of the problem assessed in our study.

Compared to other methods (e.g., Technique for Human Error Rate Prediction (THERP) or Hazard and Operability Study (HAZOP) [50]), both the HEART and FMEA are characterized by simplicity of implementation and high practical usefulness in port environments, where data availability may be limited and decision-making processes are dynamic and multi-dimensional.

3. Materials and Methods

The aim of the study deals with assessing the probability of making an erroneous decision related to the admission of an non-compliant vessel to traffic (e.g., incorrectly categorized according to the compliance group (Table 1) or in inappropriate weather conditions, etc.) on the dredged Świnoujście–Szczecin fairway, resulting from the adoption of new vessel traffic regulations (established in Port Regulation document [17]). A non-compliant vessel admitted to traffic on a waterway means the following:

• A vessel that poses a collision risk in two-way traffic;
• A vessel for which operating conditions within the fairway pose a significant threat.

An assessment of the probability of error was carried out in accordance with the procedure recommended in [50]. However, techniques used in the study were adapted to the working conditions of VTS operators; FMEA [58,59] and HEART [49,51,75] methods were used [50].

The following stages were applied to conduct the research:

• A FMEA form was prepared containing a description of the tasks and subtasks carried out in the vessel traffic planning process, the objectives pursued within each subtask, the identification of hazards and the category and type of possible errors.

The following assumptions were made when developing the form:

• Each planned decision tends toward the consent for the vessel to join the traffic within the fairway (e.g., variable weather conditions and time of day, which may interrupt the process and the prohibition of the vessel joining traffic were not taken into account), the main focus is on information flow impacted by human factors.
• Ships can pass each other on the dredged fairway; nothing prevents the decision from being made.
• Vessel traffic planning takes place at the VTS Centre Szczecin.

2.

The probability of failure was determined using the HEART method. This is a quantitative method for assessing human error. The nominal values of error probabilities were set based on the available literature [76]. It was assumed that the cause of individual human errors would be routine, due to a lack of attention and inappropriate work organization resulting from the exchange of information between decision-makers. Based on the process described, an event tree was developed, referring to the decision-making of VTS operators directly after the implementation of new vessel traffic regulations, which altered the course of the previous decision-making process (carried out before improvements). The probability of making erroneous decisions for each of the analyzed scenarios was calculated. Five scenarios of possible events (SoPEs) and their development were considered. An expert method was used to determine the values used in the analysis. The experts were experienced VTS operators and decision-makers from the Maritime Office in Szczecin.

3.

Improvements were proposed to reduce the probability of making erroneous decisions by VTS operators. These improvements were related to the implementation of a DSS and VTS operator training. As a part of the DSS, a developed decision support tool (hereinafter referred as “calculator”) was applied.

4.

The calculations of error occurrence probability using the HEART method were carried out, considering implementation of improvements. An event tree was developed for determined scenarios.

In the article presented, the analysis of the decision-making process did not directly take into account factors related to conflicts that may arise during interactions between decision-making centers. However, when calculating the risk of error using the HEART method, the appropriate values of the considered parameters addressing the relations between different decision-makers were taken into account.

The achieved research results were analyzed and compared to values indicating risk acceptability. According to the ALARP (As Low As Reasonably Practicable) principle, the boundary of unacceptable risk is 10⁻⁵ [77] (i.e., one incident in 100,000 operations). In case the risk is higher, it is mandatory to undertake reduction measures. This risk level was used to compare the calculated probability of making erroneous decisions by VTS operators.

4. Results

The research was performed according to the stages described in Section 3.

4.1. Stage 1

Risk identification was performed based on the FMEA form. The main task and subtasks in the process and the resulting objectives have been identified. A part of the decision-making process “planning of vessels for movement” carried out at VTS Center Szczecin (Step 1 at Figure 2) was considered. This task ends with the issuance of a permit for the vessel to enter the Świnoujście–Szczecin fairway. It should be noted that during each of the identified subtasks, the information related to the ship’s compliance group is processed. The FMEA form was used and the risks associated with the performance of specific tasks were identified (

Table 3. FMEA form (own elaboration).

No.	Task and Subtasks	Objectives	Potential Risks	Human Error Categories	Type of Errors	Risk Control Measures
1	Vessel traffic planning	Planning the traffic with the adoption of new vessel traffic rules	Delays in the planning process; replanning; allowing a non-compliant vessel to enter fairway	Error of input/output information flows processing by employee within organization	Lack of attention; calculation error. Communication error; lack of knowledge	Training and implementation of support programs. Elimination of possible threats; ensuring compliance with regulations
1.1	Commencement of the process for notified vessels	General traffic plan and passing; assignment of ships to compliance groups	Delays in the planning process	Error of information evaluation by employee. Lack of a clear plan	Lack of attention; calculation error	Training and implementation of support programs. Ensuring compliance with regulations
1.2	Agreement of the vessels schedule with the port’s authority	Traffic priority setting with the port’s authority	Delays in the planning process	Error of work organization. Lack of clear feedback	Communication error; lack of knowledge	Identification of critical steps for information flow management
1.3	Agreement of the vessel’s schedule with the VTS Center Świnoujście	Confirmation of the preliminary schedule of vessel traffic in Świnoujście	Delays in the planning process and replanning	Error of information evaluation by employee	Lack of attention; calculation error	Training and implementation of support programs. Elimination of possible threats
1.4	Communication of the decision to the master of the vessel/pilot	Communicate the prepared decision to the master/pilot	Allowing a non-compliant vessel to operate	Error of communication within organization	Communication error; lack of knowledge	Effective control of access to information, elimination of the risk of breaches or abuse.

). The form has been developed based on the authors’ knowledge and observations made at the VTS operators’ workplace.

4.2. Stage 2

In order to calculate the probability of the decision-making processes failure, the recommended HEART method [49] was applied. The main steps of conducted calculations are presented in Figure 3.

The Nominal Unreliability Probability ($NUP$) values, which are most relevant to the particular subtasks performed in the decision-making process, were selected using the expert method. Authors of the present article were the experts (three people). The $NUP$ values defined within the HEART method can be applied depending on task characteristics such as novelty, time pressure or unfamiliarity (

Table 4. Nominal Unreliability Probability values used in the analysis (own elaboration).

Nominal Unreliability Probability	Task Description
0.0004	Highly standardized tasks with low error probability. A simple, repetitive, well-practiced task performed under normal conditions.
0.09	Troubleshooting or decision-making task in familiar conditions, where causes and solutions are generally known. Routine, highly practiced, rapid task.
0.16	Task execution requires higher cognitive processing, judgment, and problem-solving ability under uncertain or unfamiliar conditions.
0.34	Task execution involves time pressure, stress and the need for quick decisions, possibly with incomplete information. Task execution requires a high level of comprehension and skill.
0.55	A totally new or first-time task, with no prior experience, guidance or support available. Completely unfamiliar task performed with no supervision or procedure.

). For the subtasks involving the following:

• The exchange of information between VTS operators and the port’s authority (dispatcher), as well as VTS operators and the pilot or ship master, a $NUP$ value “0.16” was adopted, referring to a set of tasks requiring high skills and knowledge (typically applied to interactions with external participants under uncertain communication conditions or incomplete information flow).
• For relations between operators from VTS Centre Szczecin with operators from VTS Center Świnoujście, a $NUP$ value “0.09” was assumed, indicating relatively simple tasks performed quickly (typically applied in standardized internal communication between trained VTS operators using predefined procedures).

In the HEART methodology, the Multiplier represents the impact of Error-Producing Conditions (EPCs) on task performance. Each EPC has a predefined maximum Multiplier value (

Table 5. Multiplier values used in the analysis (own elaboration).

Multiplier	Impact of Error	Description
1	Very low	EPC occurs occasionally and is easily mitigated by procedures.
2	Low	EPC occurs regularly and requires operator awareness to mitigate.
4	Moderate	EPC is present but partially controlled (e.g., through experience or supervision).
6	High	EPC has significant influence; communication difficulties, stress or time pressure.
8	Very high	EPC is critical; lack of control, no training and organizational chaos.

). The Multiplier values between one and eight were considered.

While selecting Multiplier values, the following justification was used:

• For subtasks 1.1 and 1.3 performed by VTS operators, Multiplier value “6” was used for tasks dealing with poor information quality, when procedures are known but occasional interpretation issues may arise.
• For subtasks 1.2 and 1.4 performed in cooperation with other participants of decision-making process (e.g., ports authority) Multiplier value “8” was applied, considering involvement of external personnel with unknown training level or unclear expectations, reflecting the increased uncertainty in communication with port authorities or vessel masters.

An Effect Proportion value of “0.1” was adopted. The mentioned values were assigned based on the classification of task types according to the original HEART methodology [49,51] and were validated through direct operational observations and documentation analysis conducted at the VTS Centers in Szczecin and Świnoujście.

The following formula to calculate Assessed Impact ($AsIm$) during the performance of single subtasks was applied:

$${AsIm}_i=\left(M_i-1\right)\times {EP}_i+1,$$

(1)

where

${AsIm}_{i }$—Assessed Impact for single subtask;

$M_i$—Multiplier for single subtask;

${EP}_i$—Effect Proportion for single subtask;

$i$—subtask during the task’s implementation, $i=1.1,\dots ,1.n.$

Based on these assumptions the probability of failure during the performance of a single subtask (${PF}_i$) was calculated as follows:

$${PF}_i={NUP}_i\times {AsIm}_i.$$

(2)

The probability of failure of the entire process ($PF$) was calculated as the multiplication of the probabilities of failure of individual subtasks (${PF}_i$).

The calculated probabilities for individual task implementation before the DSS’s implementation are shown in

Table 6. The probability of failure determined using the HEART method before DSS implementation (own elaboration).

No.	Task and Subtasks	Nominal Unreliability Probability (Step 1)	Multiplier (Step 2)	Effect Proportion (Step 3)	Assessed Impact (Step 4)	Overall Failure Probability (Step 5)
1	Vessel traffic planning
1.1	Commencement of the process for notified vessels	0.09	6	0.1	1.5	0.135
1.2	Agreement of the vessel schedule with the port’s authority	0.16	8	0.1	1.7	0.272
1.3	Confirmation of the ship schedule with the VTS Center Świnoujście	0.09	6	0.1	1.5	0.135
1.4	Communication of the decision to the master of the vessel and pilot	0.16	8	0.1	1.7	0.272
Probability of failure of the entire process						0.00135

. The steps presented in Table 6 correspond to the steps performed in Figure 3.

The analysis refers to an error in information flow used in decision-making processes related to the admission of non-compliant vessels to traffic. During the agreement of process implementation between VTS operators and other decision-making participants, an error in information flow may occur and could be identified. The probability of success ($PS$) when dealing with identifying and correcting an error in the decision is indicated as “YES” in Figure 4; the probability of failure ($PF$), referring to a situation when an incorrect decision has not been identified and corrected, is designated as “No” in Figure 4.

The probability of success ($PS$) may be calculated as follows:

$$PS=1-PF,$$

(3)

where

• $PF$—probability of failure.

Based on the calculated results presented in Table 6 by applying Equation (3), it is possible to estimate the probability of success ($PS$) for the individual subtasks under consideration:

• ${PF}_{1.1}=0.135$, ${PS}_{1.1}=0.865$;
• ${PF}_{1.2}=0.272$, ${PS}_{1.2}=0.728$;
• ${PF}_{1.3}=0.135$, ${PS}_{1.3}=0.865$;
• ${PF}_{1.4}=0.272$, ${PS}_{1.4}=0.728.$

The way to conduct calculations (Figure 4) is presented below:

• SoPE–SI: $PS={PS}_{1.1}$, $PS=0.865$;
• SoPE–SII: $PS={PF}_{1.1}\times {PS}_{1.2}$, $PS=0.135\times 0.728=0.09828$;
• SoPE–SIII: $PS={PF}_{1.1}\times {PF}_{1.2}\times {PS}_{1.3}$, $PS=0.135\times 0.272\times 0.865=0.03176$;
• SoPE–SIV: $PS={PF}_{1.1}\times {PF}_{1.2}\times {PF}_{1.3}\times {PS}_{1.4}$, $PS=0.135\times 0.272\times 0.135\times 0.865=0.00361$;
• SoPE–SV: $PS={PF}_{1.1}\times {PF}_{1.2}\times {PF}_{1.3}\times {PF}_{1.4}$, $PF=0.135\times 0.272\times 0.135\times 0.272=0.00135$.

The event tree related to planning the vessels’ movement directly after the implementation of new vessel traffic regulations is presented in Figure 4. This event tree illustrates the step-by-step process of information verification related to vessel traffic planning during the implementation of particular tasks. Each step reflects the sequential flow of information between decision-making participants: VTS Centre in Szczecin, the port’s authority and the VTS Centre in Świnoujście, as well as the vessel’s master or pilot.

The identified scenarios of possible event developments are shown in

Table 7. Scenarios of event developments within the decision-making process (own elaboration).

SoPE	Description	Outcome
SI: Process is correct	The decision-making process proceeds correctly, without disruption or information asymmetry	No action needed
SII: Process is disrupted	The decision-making process was disrupted; the next decision-making body corrected the error; the process ended correctly	The disruption causes a minor delay in the decision-making process
SIII: Process is disrupted	The decision-making process was disrupted; the next decision-making body corrected the error; the process ended correctly	The disruption causes a significant delay in the decision-making process
SIV: Process is disrupted	The decision-making process was disrupted; the next decision-making body corrected the error; the process ended correctly	The disruption causes the replanning of vessel traffic
SV: Process is incorrect	The decision-making process was disrupted; subsequent decision-making bodies did not correct the error; the process ended incorrectly and the disruption resulted in the admission of a non-compliant vessel to traffic.	Non-compliant vessel enters the fairway. The actions needed: Precise monitoring of vessel traffic; An effective post-disruption review (drawing conclusions).

. Depending on the degree of disruption in the decision-making process, specific outcomes may take place.

Considering that the decision-making process evolves dynamically, the consequence of its failure depends on the stage at which the error is or is not corrected. For example:

• If an error is detected and corrected during subtask 1.1, the process is implemented correctly (SoPE–SI);
• If an error is detected early (subtask 1.2), only a minor delay may occur (SoPE–SII);
• If an error is detected during implementation of subtask 1.3, significant delay may take place (SoPE–SIII);
• if an error is detected later (subtask 1.4), replanning of vessel traffic may be required (SoPE–SIV);
• if an error is undetected at all, it results in an erroneous decision, such as admitting a non-compliant vessel to enter the fairway; in this case a serious accident may happen (SoPE–SV).

The probability of failure of the entire decision-making process (${PF}_{SV}={1.35\times 10}^{-3}$) was calculated as the multiplication of the probabilities of failure of individual subtasks. This probability value is unacceptable according to the ALARP principle, which refers to the value of the acceptable risk level. The acceptable value is assumed to be lower than 10⁻⁵ [77]. Therefore, measures to reduce the probability of failure should be undertaken.

4.3. Stage 3

While estimating the probability of making erroneous decisions, it was assumed that the main cause of possible failure in the decision-making process is a change in vessel traffic regulations. The simplest way to eliminate errors in decision-making is by implementing a DSS and carrying out staff training. As a part of a DSS, the authors of the article additionally propose the use of a decision support tool (“calculator”) allowing the assignment of a ship based on its parameters (length, width and draught) to the appropriate compliance group (Figure 5). In addition, this tool provides information on the possibility of two ships passing each other on specific sections of the Świnoujście–Szczecin fairway. This tool was developed as an Excel file by the author of this article.

The VTS operator may provide the parameters of passing vessels A and B to the first two tables (shown in Figure 5); the tool shows the number of the appropriate compliance groups for these ships (according to Table 1). Based on the introduced data, the tool reveals the possibility or impossibility for these vessels passing each other on five different sections of the Świnoujście–Szczecin fairway. As a part of risk reduction measures and DSS implementation, the tool was put into use and training of VTS operators was carried out in the Maritime Office in Szczecin.

4.4. Stage 4

After the implementation of the DSS, the value of Nominal Unreliability Probability was reduced to the value of “0.0004” for subtasks 1.1 and 1.3. The probability values for subtasks 1.2 and 1.4 were left unchanged, because the improvements concerned only the tasks performed by VTS operators. It was assumed that the implementation of the DSS significantly helped VTS operators to gain confidence and knowledge in their decision-making. Other participants in the decision-making process were not covered by the proposed training. The implementation of the DSS (including “calculator” and training) for port authority employees and pilots/ship masters was not carried out. The calculated probabilities of failure during performing single subtasks after DSS implementation are shown in

Table 8. The probability of failure determined using the HEART method after DSS implementation (own elaboration).

No.	Task a1.	Nominal Unreliability Probability (Step 1)	Multiplier (Step 2)	Effect Proportion (Step 3)	Assessed Impact (Step 4)	Overall Failure Probability (Step 5)
1	Vessel traffic planning
1.1	Commencement of the process for notified vessels	0.0004	6	0.1	1.5	0.0006
1.2	Agreement of the vessel schedule with the port’s authority	0.16	8	0.1	1.7	0.272
1.3	Confirmation of the ship schedule with the VTS Center Świnoujście	0.0004	6	0.1	1.5	0.0006
1.4	Communication of the decision to the master of the vessel and pilot	0.16	8	0.1	1.7	0.272
Probability of failure of the entire process						2.66 × 10−8

.

An event tree for the analyzed decision-making process is presented in Figure 6.

The event tree (Figure 6) shows the structure of the decision-making process after implementing corrective measures (DSS), such as VTS operator training and applying a dedicated decision support tool (“calculator”). A significant reduction in the probability of failure is observed at every stage of the processes’ performance (compared to the previous version of event tree (Figure 4)).

It is worth noting that:

• The probability of success at the first stage (corrected information flow) has increased to $PS=0.9994$, indicating reduced errors in information flow (SoPE–SI).
• The probability of a critical failure—i.e., an incompatible vessel entering the fairway without error detection (SoPE–SV)—was decreased drastically to ${PF}_{SV}=2.66\times {10}^{-8}$. This probability value is acceptable according to the ALARP principle [77].
• The implementation of particular subtasks (SoPE–SII/SIV) deals with substantially lower probability values (compared to processes before DSS implementation).

The achieved results analysis revealed that combining training with a well-designed decision support tool enhances both the accuracy and speed of the operator’s responses to changes in Port Regulations that contain new vessel traffic rules. Moreover, the calculated probability of failure of the entire process analyzed decreased to the acceptable level (according to the ALARP principle), confirming that the introduced corrective actions are both effective and justified.

5. Discussion and Conclusions

The aim of the research was to assess the probability of making erroneous decisions related to the admission of non-compliant vessels to traffic on the dredged Świnoujście–Szczecin fairway after the introduction of new vessel traffic regulations. The probability of making erroneous decisions was calculated for cases before and after the implementation of the DSS. The research results contributed to the expansion of knowledge in the field of new vessel traffic regulations’ impact on the probability of making erroneous decisions related to the admission of non-compliant vessels to traffic on the dredged Świnoujście–Szczecin fairway, considering the implementation of a DSS. Moreover, it was shown that implementation of specific improvements (in particular the DSS) may lead to a reduction in probability of making erroneous decisions by VTS operators that prove the effectiveness of the DSS considered. The achieved outcomes were taken into account during the mentioned DSS’s development and will impact its future improvement.

Research was conducted using the FMEA and HEART methods recommended by [50]. It was revealed that directly after the introduction of new vessel traffic regulations, the probability of making erroneous decisions was unacceptable; for the worth scenario it was ${PS}_{SV}={1.35\times 10}^{-3}$. Therefore, to improve vessel traffic planning, specific measures were implemented and the DSS was applied. The measures introduced included training of VTS operators on the following:

• Changes in the traffic regulations and ship grouping;
• The use of a developed decision support tool.

The results of the analysis indicate a significant reduction in the probability of making erroneous decisions after the implementation of the improvements. This finding indicates that the implementation of the DSS is effective. However, verification of the DSS’s effectiveness requires further investigation. In order to confirm the effectiveness of the solutions applied, an empirical analysis of the impact of the developed tool and training on the actual level of decision-making errors performed by VTS operators is planned. It will also be crucial to collect operators’ feedback and monitor the effectiveness of the tool’s usage in real operating conditions.

Recommendations related to reducing the risk of making erroneous decisions are presented in

Table 9. Recommendations related to reducing the risk of making erroneous decisions during vessel traffic planning (own elaboration).

Task/Subtasks	Recommendations
Vessel traffic planning	Implementation of self-learning real-time risk assessment systems that operate in “long-term planning” modes, which would limit the need to use old communication methods. Regular training of VTS operators in vessel traffic management in dynamic operating conditions.
Commencement of the process for notified vessels	Standardization of operational start-up protocols for notified vessels to reduce the risk of misinterpretation of commands.
Agreement of the vessel schedule with the port’s authority	Use of a DSS that will automatically verify the compliance of the ship list with the port schedule. Improvement of a common data sharing platform between VTS operators and the ports authority based on advanced algorithms.
Confirmation of the ship schedule with the VTS Center Świnoujście	Use of real-time data confirmation protocols; implementation of automatic ship schedule synchronization systems between VTS centers.
Communication of the decision to the master of the vessel and pilot	Carrying out regular audits and analyses of cases of the misinterpretation of messages to adjust procedures and improve the effectiveness of communication during decision-making.

.

It should be noted that the research results are limited to the exact case study’s analysis, mainly vessel traffic planning on the Świnoujście–Szczecin fairway considering VTS operators’ perspectives. Nevertheless, the approach to conduct the assessment of the probability of making erroneous decisions related to the admission of non-compliant vessels to traffic on the fairway after introduction of new vessel traffic regulations was developed. This approach may be applied to assess the probability of making erroneous decisions related to the admission of vessels to traffic within other specific areas. The possibility of conducting similar assessments for other waterways will be considered in our future research.

Moreover, theoretical judgments and a qualitative approach were applied in the present research study. As a result of the performed research, the base of knowledge that could be used during further investigations was created. The nominal values of the probability of making an erroneous decision were set based on data available in the literature [76], which may also impact the research results. However, due to the specific operating conditions on the Świnoujście–Szczecin fairway, it is planned to additionally validate these values based on an analysis of actual incidents in this area. For this purpose, specific databases should be created.

Two methods were applied to solve the set research problem (the HEART and FMEA methods), which could also impact the research results. The application of other risk control techniques for both threat identification and prevention, as well as the correction of managerial decisions, will be considered in our future research.

Furthermore, potential risks related to the decision-making processes carried out by VTS operators were identified based on the authors’ knowledge and observations. It should be noted that new risks and challenges during VTS operators’ work may appear. Therefore, it will be reasonable to repeat the research and conduct investigations a few years after the implementation of the new regulations. This will allow us to assess the probability of making erroneous decisions related to the admission of non-compliant vessels to traffic under other conditions of the fairway’s operation and compare the results.

The directions of the authors’ future research will deal with the application of a quantitative approach to assess the risk of decision-making processes related to vessel traffic planning on the Świnoujście–Szczecin fairway; empirical validation of the developed approach with operational data will be considered. Moreover, the analysis of information uncertainty occurring during decision-making processes on vessel traffic planning within the Świnoujście–Szczecin fairway, as well as detailed modeling of the decision-making process and improving the DSS used by VTS operators will be carried out.

Research results may be interesting to VTS operators, maritime offices and port authorities involved in planning and monitoring vessel traffic on fairways.