A Probabilistic Analysis of Tanker Groundings

Abstract

The culture, design, and operation of the maritime industry all contribute to create an error inducing system. While risk acceptance and risky behavior are often attributed to the “traditions of the sea,” the risks associated with sea transportation are no longer restricted to the domain of the seafarer. Accidents such as the Exxon Valdez, Braer, and the more recent Sea Empress groundings have increased public awareness of these risks. As oil tankers have gotten larger, the tolerance for error has decreased, and the consequences have increased. However, society’s concerns are not as much about the proportionate increase in tanker size, as the disproportionate increase in the potential environmental impact. While the tanker industry has been identified by the USCG has a high -risk industry, the USCG has also stated that the industry has a high potential for improvement. A systematic approach must be undertaken to effectively identify tanker accident risks and consequences so that they can be minimized by appropriate safety measures. This paper outlines three levels of assessment that lead to the ultimate probability of oil pollution producing an impact. It concentrates on one aspect of a Level 1 Probabilistic Risk Analysis (PRA) for tanker groundings. The approach utilizes fault trees and event trees and incorporates The Human Error Rate Prediction (THERP) data to quantify individual errors.