The objective of speed limit is not simply to reduce the speed but to introduce smooth traffic flow and to prevent marine accident by allowing ships to pass at a constant speed. In addition to this, speed limit is also used as a means of increasing calmness by reducing ship wave.
In Korea, speed limit is designated in 21 ports among 31 ports in total. However, necessary standards and instructions are not ready yet so the presentation of problems whether the speed limit is appropriate and reasonable.
The objective of this study is to develop a model of setting speed limit of ships on the sea. Speed limit shall not be decided only by considering the safety of ships but also efficiency, economic feasibility, surrounding facilities of port and waterway and influence on neighboring structures and users of facilities.
Setting a model of speed limit of ships at sea or introducing guidelines has not been found anywhere not only in Korea but also in other countries. Since this thesis is the first study to suggest on setting a model of speed limit and guidelines, this thesis is valuable.
This thesis was conducted by going through the following procedures. The obtained results are as follows In Chapter 2, the relation between speed, safety and effect of speed limit were considered based on the existing studies. The accidents are not increased just because speed is high. It is the general opinion in marine traffic engineering that the rate of accidents is high when there is a big variance in speed. and ports where speed limits were designated and operation conditions are investigated. In Korea, only 21 ports among 31 ports set speed limits, even under the similar circumstances, speed limits were varied from 5kts to 15kts. In most of local ports, actually STW (Speed Through the Water) is applied therefore it has been difficult to manage speed limit. For the top 3 busy ports(Busan, Yeosu․Gwangyang and Incheon port), the present condition of these port was investigated. In Incheon and Busan port, more than 57% of ships violated the speed limit, where Busan port has the highest violation rate.
In Chapter 3, the Delphi method was used to obtain the factors to be considered in deciding speed limit. Five primary elements (natural conditions, ship condition, traffic condition, waterway condition, outside support and other conditions etc.) and 23 sub-factors were finally obtained by Delphi method. Based on these 23 factors, the degree of the importance of use was obtained through AHP method (Analytic Hierarchy Program) and the weight was assigned for the items which importance of use is very high. This weight is utilized in the comprehensive results of traffic safety evaluation.
In Chapter 4, the speed limit model is suggested in order to obtain the rational value of speed limit. There are 6 stages starting from differentiating sea area division and to the stage 6 of implementation & assesment. Two(2) kinds of decision formulas are suggested both in case of reflecting the navigation speed and of not reflecting the speed.
In Chapter 5, the speed limit model suggested in Chapter 4 was applied to the port of Busan to evaluate the effectiveness of the model. Consequently, the speed limit in the approaching channel was 12.9 knots and 11.6 knots on the maneuvering area. The speed limit of approaching channel was 9.3 knots and 6.9 knots for the maneuvering area, not reflecting the navigation speed.
This study focuses on what kind of factors and process to be considered. and what kind of process to accept in order to decide the rational speed limit. However, there are some limitations in suggesting a perfect speed limit model and to generalize the model. Therefore, it is necessary to apply the model to another port and to make up for the factors to be considered and evaluation criteria in detail.