The vehicle routing and scheduling problem has been studied with much interest within the last four decades. In this paper, some of the existing literature dealing with routing and scheduling problems with environmental issues is reviewed, and a description is provided of the problems that have been investigated and how they are treated using combinatorial optimization tools.
Although the fact that the major target of RHM is the minimization of the risk, there is no universally accepted definition of risk (for a survey on risk assessment, see @cite_89 ). The risk caused by hazmat transportation depends on many factors, the most important of which are: the risk categories (explosion, toxicity, radioactivity, etc), the transportation mode, the affected agents (population, territorial infrastructures and natural elements), the meteorological conditions and the temporal factor. It is pointed out in @cite_48 that the evaluation of risk in hazmat transportation generally consists of the evaluation of the probability of an undesirable event, the exposure level of the population and the environment, and the degree of the consequences (e.g., deaths, injured people, damages). In practice, these probabilities are difficult to obtain due to the lack of data and generally, the analysis is reduced to consider the risk as the expected damage or the population exposure.
@cite_48 @cite_89
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We survey research on hazardous materials transportation in the areas of risk analysis, routing scheduling and facility location. Our focus is primarily on work done since 1980, and on research which is methodological rather than empirical. We also limit our focus to transport by land-based vehicles (truck and rail), excluding pipeline, air and maritime movements. The review traces the evolution of models from single-criterion optimizations to multiobjective analyses, and highlights the emerging direction of dealing explicitly with distributions of outcomes, rather than simply optimizing expected values. We also indicate examples of work which integrate risk analysis with routing, and routing with facility location. We conclude with a discussion of several aspects of hazardous materials transportation which offer important challenges for further research. The transport of hazardous materials is an important strategic and tactical decision problem. Risks associated with this activity make transport planning difficult. Although most existing analytical approaches for hazardous materials transport account for risk, there is no agreement among researchers on how to model the associated risks. This paper provides an overview of the prevailing models, and addresses the question "Does it matter how we quantify transport risk?" Our empirical analysis on the U.S. road network suggests that different risk models usually select different "optimal" paths for a hazmat shipment between a given origin-destination pair. Furthermore, the optimal path for one model could perform very poorly under another model. This suggests that researchers and practitioners must pay considerable attention to the modeling of risks in hazardous materials transport.