Abstract: Bridge Team is organized by plural persons to perform safe navigation in difficult situation for one duty officer like restricted water or congested area. The construction of Bridge Team is changed corresponding with the degree of difficulty in navigational condition. This means Bridge Team is expected to show higher ability than single officer by sharing tasks and integrating each member's functions. However, Bridge Team sometimes exposed to the danger of marine casualty, when Bridge Team is organized idly and its function does not work sufficiently.

 The purpose of this study is to analyze the functional construction in Bridge Team, and to confirm its effectiveness to prevent marine casualty. Firstly, author analyzed the navigation into tasks, and classified essential function to attain each task into three kinds as the function of ship handling technique, the function of communication, and the function of cooperation. Secondly, results of maneuver that performed by Bridge Team were analyzed to prove the adequacy of the concept about three functions. Finally author confirmed the functional construction and the effectiveness of Bridge Team utilizing Fault Tree Analysis. The obtained results are summarized as follows:

 As vessels became larger and traffic condition became more serious in certain place, the human, material and environmental damage by a marine casualty comes more serious. In difficult maneuvering conditions, such as traffic route, restricted visibility area, advanced and adequate maneuver is always required to ship operator. Bridge Team is constructed on the purpose of preventing marine casualty in these difficult navigational conditions. It is expected for Bridge Team to show the higher ability than not only the ability of each operator, but also the sum of each member's ability by cooperating each other.

　

 To investigate the function of Bridge Team, author analyzed the maneuvers into tasks and proposed a concept about essential function for Bridge team. And the proposed concept was proved through analyzing actual result of maneuver in ship handling simulator. Further more, author analyzed the Fault Tree of marine accidents and confirmed the functional construction in Bridge Team.

　

 In normal condition, one navigator and one crew perform each ship handling; this state is called "Single Watch". Single Watch accomplishes most of navigational objectives. As vessel comes to the difficult navigational condition, number of bridge member is increased corresponding with the difficulty of navigational condition. The state of navigational watch that the number of watch member increased is called "Bridge Team".

　

 Bridge Team accomplishes the objectives of navigation by performing tasks such as avoiding other ships, docking, etc. Authors analyzed the navigation condition in each condition performed by Bridge Team into tasks. Table I shows divided tasks in each condition of navigation.

　

 For example, the navigation of passing narrow channel is divided into the task of general navigation, controlling ship's position, altering course, reducing ship speed and avoiding other vessels. And the navigation under the condition of congested area is divided into the task of general navigation, altering course and avoiding other vessels. Moreover, each task is developed into elemental techniques such as position fixing, watch keeping, instrument manipulate and etc. To develop the tasks into elemental techniques means to develop each member's function and the construction of function in Bridge Team.

　

　

 Figure 1 shows an example of each member's functional division in avoiding other vessel. In this condition, master analyzes and decides the way of avoiding other ship, based on the radar information from second officer (2/O), VHF information from third officer (3/O) and visual information by all members of Bridge Team.

　

　

 In this way, each member of bridge team shares the function of ship handling techniques. In order to combine each member 's function as a team, it is necessary to share information about the navigation. Function of communication is the function to share navigational information among members. Furthermore, function of cooperation to accomplish the common objective in Bridge Team is also necessary.

　

　By above-mentioned reason, authors classified the essential function of each member into three kinds of functions. The contents of these three functions are discussed in following sections.

　

3.1 Function of ship handling technique

　

 Functions on ship handling are understood to be composed of nine elemental techniques. The principal contents of nine elemental techniques are as follows;

　

1) Watch keeping

 The technique to identify and recognize the moving targets and the fixed targets and to gather information of direction, distance and speed and to estimate the future situation of the targets.

　

2) Positioning

 The technique to find the position of ship by selecting and recognizing proper obstacles using visual information, radar and etc.

　

3) Maneuvering

 The technique to control course, speed and ships position using steering, main engine control and etc.

　

4) Instrument Manipulation

 The technique to properly utilize instruments for watch keeping, positioning, ship handling and etc.

　

5) Communication

 The technique to exchange information among the bridge and inside and/or outside of the ship.

　

6) Rule of Road

 The technique to handle the ship based on the Regulations for Preventing Collision at Sea and etc.

　

7) Planning

 The technique to gather information concerning the navigational environment conditions and to make an operational plan and a navigational plan.

　

8) Emergency

 The technique to cope with malfunction of a main engine, a steering system, etc. and a rescue activity properly.

　

9) Management

 The technique to make good use of member 's ability and raise the bridge team's performance.

　

 In the case of Single Watch, objectives of navigation are accomplished by duty officer's function of ship handling technique. But in the case of Bridge Team, each member assigns the function of ship handling technique. So the objectives of navigation cannot be accomplished though each member attains just assigned function.

　

 By this reason, it is necessary to combine assigned functions of ship handling technique and show the ability as a team. The following two functions are to combine each member's function and show the ability as a team.

　

3.2 Function of communication between members

　

 Function of communication is to exchange information each other and hold the information in Bridge Team in common. On the other side, communication with outside of the team, as other ship or vessel traffic service and etc, are also included to communication in function of ship handling technique.

　

3.3 Function of cooperation

　

 Function of cooperation is to accomplish higher technique by combing each member's function under common objective. The specific contents of this function can be shown as follows;

　

1) Function of collaboration

 Function to combine each member's ship handling technique and accomplish higher technique under the common objective in Bridge Team.

　

2) Function of management

 Function to assign the jobs and to check the accomplishment of assigned job.

　

3) Function of compensation

 Function to compensate a lack of other member's attainment.

　

 Function of communication is to be considered one part of function of communication in elemental technique, and function of cooperation is included into management in elemental technique, In the viewpoint of Bridge Team function, these two functions should be paid special attention.

　

 To prove the adequacy of the concept for Bridge Team function, authors analyzed the results of ship handling in ship handling simulator. Generally, function of ship handling technique is needed for both Single Watch and Bridge Team for operation of the ship. So it is necessary to clarify the effect that caused by function of communication and cooperation.

　

4.1 Effect of the function of communication

　

　

　

 Figure 2 and 3 show the example of altering course maneuver that affected by the function of communication. In the case of figure 2, 3/O fixed ship's position at 1.2 miles before altering course point and reported it to master immediately. Due to the report, master ordered "port 10" at proper timing at 600 meter before the point. The maximum deviation of ship's position after altering course was 190 meters right side from planned course line.

　

 In the case of figure 3, 3/O fixed ship's position at 1.9 miles before altering course point, but did not report it to master. Next, 3/O fixed ship's position at 1.0 mile before altering point but reported it at 300 meter before the point. As a result of delaying of report, the maximum deviation of ship's position after altering course was 560 meters right side from planed course line, even though master ordered "port 15".

　

 In these cases, both of 3/O attained the assigned function of ship handling technique such as positioning, Instrument manipulate. The deference occurred between two maneuvers due to 3/O's function of communication. From these analyses, the function of communication should be treated as important function for Bridge Team.

　

4.2 Effect of the function of cooperation

　

 Figure 4 show an example of reducing ship's speed maneuver that effected by the function of cooperation. In case A in Fig.4, 2/O paid extra attention to the following ship during reducing her speed and report the distance to the following ship at 6 and 5 cables. Due to 2/O's lookout, master noticed and contacted with the following ship and understood the intention of maneuver each other. The distance between own and following ship was kept in proper value.

　

　

 In case B, no one paid extra attention to the following ship during reducing ship speed. As a result, the following ship contacted using VHF at distance 2 cables from own ship.

　

 In these cases, 2/O's cooperation toward common objective of reducing ship speed influenced to the result of maneuver. Therefore, the function of cooperation should be also treated as important function for Bridge Team.

　

 In same way, more than 80 deferent result of ship handling that influenced by the functions of Bridge Team, are analyzed. As a result of these analyses, it is obtained that the function of Bridge Team should be focused on the function of communication and function of cooperation. The elemental techniques above mentioned are needed for ship handling, the technique of communication and management in developed 9 techniques are specially important for the competence of Bridge Team from the viewpoint of BRM. Based on above-mentioned concept, author investigates the appropriate process to accomplish tasks and effectiveness of Bridge Team, from the viewpoint of improvement in safety navigation.