One of the more frequent uses of risk analysis in hazardous materials transportation is in the analysis of alternative routes. The analysis techniques can usually be characterized either as a simplified risk indicator or as a complete probabilistic risk analysis. In the simplified risk indicator approach, factors that are constant (or nearly constant) for all alternatives are neglected to make computations easier. Complete probabilistic risk analysis provides quantitative evaluations of consequences such as fatalities or injuries, as well as the associated frequencies. Gaining the increased level of information provided by complete probabilistic risk analysis requires more effort at greater cost than does a simplified risk indicator analysis. Both analysis techniques were used to study one railroad and two highway routes for transporting chlorine. None of the simplified risk indicators used produced a ranking of alternatives consistent with the ranking of the complete probabilistic risk analysis for both transport modes. For the truck transport mode, one risk indicator produced results consistent with the complete probabilistic risk analysis results. The validity of the simplified risk indicator approach depends on understanding the assumptions associated with the indicator selected.

Hazardous materials are transported safely every day. Spectacular accidents, although relatively infrequent, are reminders of the harm that can be done and underscore the need to become more aware of these risks and attempt to reduce them. Routing of hazardous material shipments to avoid highdensity population areas and highways with high accident rates is one way to reduce risks. One of the more frequent uses of risk analysis in hazardous materials transportation is to assess alternative routes.