Risk assessment and decision making strategies in dangerous good transport. From an Italian case study to a general framework

The relentless drive of consumerism has required increased quantities of dangerous goods to be manufactured, transported, stored and used year on year, despite the relative recent move towards “inherent safe” materials. The safety and efficiency of road transport is to be considered a strategic goal in particular in those countries, like Italy, in which about 80% of goods is transported by this means with a 30% increase with reference to the 2010 forecast. Moreover, recent severe accidents, like the Monte Bianco tunnel one, have emphasised the problem, making it clear that the present system does not function optimally and that the risk connected to dangerous goods transport is comparable with the fixed plants one. Generally speaking, the concept of risk is the relation between frequency and the number of people suffering from a specified level of harm in a given population from the realization of specified hazards. The recent EEC Directive 96/82/EC implies the evaluation of risk in highly industrialized areas by means of Quantitative Area Risk Analysis techniques. It can be noted that certain dangerous substances are transported along particular Italian road sections in quantities that would exceed the threshold for safety notification or declaration, set down in Italy by Seveso II Directive, if stored in a fixed installation. As reported by different researchers, a specifically tailored QRA methodology can represent an effective tool to assess the risk to people associated with the transport of dangerous substance. The risk from dangerous goods transport by road and strategies for selecting road load/routes are faced in this paper, by developing a site-oriented framework of general applicability. Poor appreciation of factors related to road conditions such as road class, designated speed limits, traffic density, as well as of the population characteristics, is likely to result in a risk assessment insensitive to route specifics and over- or under-estimating the overall level of risk. It was therefore chosen to develop a high level of detail in the frequency model, by considering in-depth the traffic accident environment; a “cautious best estimate” approach was employed adopting either realistic and directly detected assumptions, or conservative overestimating hypotheses. Contrary to other models, this approach considers the risk from normal traffic accidents in addition to the risk from the major hazard aspects of the transport of dangerous substances.