Risk Assessment: Theory, Methods, and Applications

CHAPTER 6

ACCIDENT MODELS

Accident models form the basis for all hazard analysis and risk assessment techniques.

—Leveson (2004)

6.1 INTRODUCTION

To understand the mechanisms of accidents and to develop accident prevention and control strategies, it is essential to know about and learn from past accidents (Khan and Abbasi, 1999). Accident data are therefore collected and stored in various databases (see Chapter 7), and accident models have been developed to support accident investigations.

Although accident investigation is outside the scope of this book, it forms the basis for much of the material presented. This is because accident models influence our perception of potential accidents and our approach to risk assessment.

The first accident models were very simple and attributed accidents primarily to single technical failures. A bit later, human factors and human errors were included in the models. Current accident researchers realize that systems also consist of societal, organizational, and environmental elements in addition to technology and individuals, which should all be integrated into the accident model (e.g., see Leveson, 2004; Qureshi, 2008).

Many accident models are focused primarily on occupational accidents and are, as such, outside the scope of this book. Brief descriptions of some of these models are included for historical reasons, mainly because we can learn from them and because they have formed the basis for more complex models of major accidents.

6.1.1 Accident ...