Özgecan S. Uluscu, Birnur Ozbas, Ilhan Or and Tayfur Altıok. SIMULATION-BASED RISK ANALYSIS OF MARITIME TRANSIT TRAFFIC IN THE STRAIT OF ISTANBUL

Abstract. The Strait of Istanbul, the narrow waterway separating Europe from Asia, holds a strategic importance in maritime transportation as it links the Black Sea to the Mediterranean.  It is considered as one of the world’s most dangerous waterways to navigate.  Over 50,000 transit vessels pass through the Strait annually, 20% of which carry dangerous cargo.

The goal of this research is to analyze the risks involved in the transit vessel traffic in the Strait of Istanbul. We have developed a mathematical risk model to be used in a risk mitigation process to improve safety in the Strait. In the first step of the risk analysis, the transit vessel traffic system in the Strait of Istanbul has been thoroughly analyzed and a simulation model was developed.  The model considers traffic rules and regulations, transit vessel profiles, pilotage and tugboat services, local traffic, meteorological conditions such as current, fog and storm and geographical conditions.  In addition to transit vessel traffic through the Strait, the current vessel scheduling practices were modeled using a scheduling algorithm. This algorithm was developed through discussions with the Turkish Straits Vessel Traffic Services (VTS) to mimic their decisions on sequencing vessel entrances and direction of the traffic when single lane practice is used.

Regarding risk assessment, two sets of factors are used to evaluate the risk of accident in the Strait: the probability of an accident and its potential consequences, as evaluated at various points along the Strait. Experience has shown that maritime accident occurrences can be very dissimilar from one another and therefore, probabilistic analysis of accidents should not be done independent of the factors affecting them. Thus, in this study, we have focused on the conditional probability of an accident, under a given setting of various accident causing factors. Unfortunately, historical accident data is by far insufficient for a proper statistical consideration of all possible settings of these factors. Therefore, subject-expert opinion is relied upon in estimating these conditional accident probabilities. We have used a particular expert-opinion elicitation  procedure from which accident probabilities are extracted through questionnaires focusing on pairwise, uni-dimensional comparisons of factor settings (while keeping the remaining factors at pre-determined fixed levels). Assessment of the consequences of a given accident (in terms of its effects on human life, traffic efficiency, property and environment) was also accomplished using a similar approach. In other words, a mathematical model is developed based on probabilistic arguments, historical data and subject matter expert opinions.  

Finally, by integrating these assessments into the developed simulation model, the risks observed by each vessel at each risk slice are calculated in regard to the natural and man-made conditions surrounding. A scenario analysis is performed to evaluate the characteristics of the accident risk as the vessel moves along the Strait. This analysis allows us to investigate how various factors impact risk. These factors include vessel arrivals, scheduling policies, pilotage, overtaking, and local traffic density. Policy indications are made based on the results of these scenarios.