Hazardous Materials Transportation By Road: Risk-analysis-based Optimal Routing Methodology

Along with the development of industrialized societies, the production capacity and transport volumes of hazardous materials (hazmat), or dangerous goods (DG) rapidly boost annual year, which results in an increasing potential danger to human health and natural environment. In China, about 95% hazmat must be transported from producers to end-users, more than 80% amount of which are through road, and annual traffic volume is up to near two hundred million tons. In resent years, due to the increasing of hazmat shipment volumes, high road accident rates and poor safety management level, some catastrophic accidents involving hazmat transport frequently occurred, which usually resulted in high casualties and great environment damage. Clearly, hazmat road transport is not only a hot issue of societal public safety, but also an important strategies and tactics decision-making problem. In this paper, in order to reduce hazmat transport risk for neighboring population and environment, a risk- analysis-based optimal routing methodology for hazmat transport by road is proposed, which supports the decision associated with safety management, optimal routing and emergency response for hazmat between local government and carriers, and perfects risk assessment theory and methodology on the moving hazard sources.Firstly, the literature pertaining to risk assessment and optimal routing of hazmat transport by road is reviewed, and the current state and some questions of the art and theory and methodology used in previous hazmat transport management, risk analysis and optimal routing are identified. Based on the statistic analysis of typical hazmat transport accidents cases, the characteristics and rules of accidents are investigated as well as control countermeasure, and the route dependent risk factors and route independent risk factors are identified. Risk characteristics of transport hazmat are depicted by the hazmat average weighted risk rank and the modifying factors of accident-proneness. On this basis, by identifying transport network, vehicles or traveling risk sources and accident impact areas, a new comprehensive systematic procedure to assessment hazmat transport risk is faced, introducing the modifying factors of accident-proneness and three kinds of risk enhancing or mitigating factors including intrinsic road characteristics, meteorological conditions, and traffic conditions. Furthermore, a route-oriented population risk and environment risk models and a rapid risk rating index approach are presented. The individual risk and societal risk models integrated with death probability coefficient of neighboring population along the hazmat route are analyzed, and the acceptability risk criterion on hazmat transport is discussed.Secondly, according to the above-described risk assessment technique and methods for hazmat during road transport, the essential meanings, figures, principles and methods of a risk-analysis-based optimal routing methodology are illuminated, and a new and general framework for optimal routing of hazmat transport and bi-level management mode between local government and carriers are brought forward. The benchmark of optimal routing problem is dependent on the exposure population risk along the road, and the assessment framework to determine the best path of hazmat transport by road is built, which includes hazmat attributes and classifies, road characteristics, impact population distribution, traffic environmental condition, emergency response capability, transport cost and so on. It is emphasized on the scale weighted technique of single objective routing and the Pareto optimal method of multi-objective routing. Moreover, the minimum hazmat accident probability path and the least population exposure path are searched by adopting impedance-adjusting node labeling shortest path algorithm and link labeling shortest path algorithm, respective. Additionally, the influence of weather condition on hazmat routing and the characteristics of hazmat accidents probability and impact population density varying with time are discussed, and a population risk model with time attribute is presented to search the minimum population risk at the best time. And the optimal routing of hazmat in time-varying, stochastic road transportation is also investigated deeply. Thirdly, the case study for liquefied chlorine road transport in Tientsin region was systematically investigated, and quantified the release probability, catastrophic consequences, population risk, environment risk and other routing criterions, some of which were shown by the ArcGIS system. According to the above-proposed risk assessment and routing methods, the optimal routing for liquefied chlorine transport by road was determined, and it reduced neighboring population and environment risk for the used route. The case study suggests the route-oriented risk assessment model determine the risk level of hazmat during road transport well and truly, and the optimal routing methods based on the population risk along the used route decrease hazmat transport accidents frequency and catastrophic consequences and help the associated routing decision-making for hazmat.