Communication and Interpretation of Results of Route Risk Analyses of Hazardous Materials Transportation by Railroad

material shipments (10–14). Rerouting hazardous materials shipments with the objective of reducing risk is complex because of the many variables that interact to affect risk. Quantitative risk analysis (QRA) of hazardous material transportation dates to the 1970s. Although advances in methodology continue, QRA has matured to the point that it is an effective tool and has been used to inform decisions in a variety of contexts. However, risk analysis, especially route-specific analyses, often requires sophisticated analytical techniques and large quantities of data and can produce a bewildering number of numerical results. The challenge for risk analysts is to interpret these large quantities of results and convert them into useful information and effectively communicate with risk managers and other interested parties (15–17). In 2008 the U.S. Department of Transportation issued the interim rule HM-232E, requiring U.S. rail carriers to gather information on the products, routes, and risk factors related to shipments of toxic inhalation hazard (TIH) materials and to determine the security risks to high-consequence locations. Consequently, railroads and government are now engaged in the process of conducting large-scale route risk analyses and will soon be in the position of having to interpret the results and consider their effect on policy. The purpose of risk analyses is to provide decision makers and others with objective information about how to effectively manage risk. In some instances, it may also be used to help gain an understanding of how to most efficiently choose among options to reduce risk. If the results are too complex to understand or are presented in a manner that is prone to misinterpretation, these objectives will not be achieved and could lead to inappropriate conclusions and decisions. The objective of this paper is to illustrate some of the approaches to the presentation of route risk analysis results that will aid in their proper interpretation and communication. The results used in this paper are based on a case study of shipments of one hazardous material on the North American railroad network. A review is presented of the basic risk analysis method used, but more complete descriptions of risk analysis methodologies can be found elsewhere (18, 19). The primary purpose here is to use the results to illustrate the techniques that have been developed to organize and present results to enhance communication and interpretation. Different metrics and approaches to normalization of the results are introduced to allow insight into risk management and planning. A number of new graphical methods have been developed to enhance communication of the risk results and to facilitate more effective consideration of risk mitigation options. A graphical approach to evaluate the Communication and Interpretation of Results of Route Risk Analyses of Hazardous Materials Transportation by Railroad