Aiming at realization of safer and more effective marine transportation, a national project of a highway network on sea surface has been progressed in Japan. A high-speed transportation in congested sea area is one of the key items to be realized in the project. As each high-speed craft (HSC) has its peculiar configuration and mission, safety assessment of its navigation should be evaluated taking traffic condition, craft performance, navigation aids and human operators corresponding to each craft into account. A procedure of the safety assessment based on ship handling simulator experiments is proposed as follows: About a high-speed craft to be assessed, a traffic environment in service sea area, maneuvering performance of HSC, maneuvering interface, sight from the navigation bridge are appropriately modeled and installed in a simulator. According to appropriate scenarios, simulator experiments are executed with expert mariners as examinees. The results should be analyzed as follows. 1) To confirm adequacy of the experiments by examinees' subjective evaluation, to show the resulting maneuver to be safe and to confirm HSC to be clearly identified. (2) To show less duration and less counts of obstructed condition in HSC experiments than ordinary-speed ship by objective evaluation based on OZT. Objective evaluation based on OZT <Evaluation conditions> 1) To keep constant HSC speed. 2) Course change within +/- 30degrees allowed. 3) Evaluate from 0.5 NM to 2.0 NM around HSC. 4) Radius of virtual circle of target ship is set as 0.07 NM(130m) Ambiguity in speeds of HSC and target ships is +/- 1 Knot (Note) These conditions should be modified according to each assessment. <Procedure of Evaluation> 1) To divide courses within +/- 30degrees into 12 zones 5 degrees width each and to count number of zones with more than 2 degrees gap of OZT. 2) OZT gap should be checked from 0.5 NM to 2.0 NM around HSC and to get the Free Zone Number by counting zones with gap(s). 3) When the Free Zone Number=0, re-evaluation should be done at the point 0.5 NM behind the most distant point without obstruction by OZT. 4) To get durations and count of the Free Zone Number=0 (obstructed condition) and to evaluate safety margin in decision making to maneuver in comparison to those of ordinary speed ships. The procedure comprises suitable modeling and installation to the simulator, adoption of the typical and most difficult scenarios and combination of expert mariners' subjective evaluation and objective evaluation with appropriate indices. A safety margin based on OZT (Obstacle Zone by Targets) is also proposed as an appropriate index for objective evaluation of high-speed navigation in congested sea area (Figure 1.). [GRAPHICS] .
