Risk-based transportation planning practice: Overall methodology and a case example

We are faced with various types of risks in our everyday lives and continue to be exposed to new risk sources. Decision makers are continually faced with deciding whether a new risk source should be allowed in a particular community. Before making such decisions, it is desirable to know what the existing risks are, and what additional risks a new facility would bring. Then, if there are established guidelines for risk acceptability, planning decisions can be made so that some segments of the society are not exposed to unduly high risks, especially risks over which they may have very little control. Quantitative risk assessment (QRA) techniques are playing an increasing role in analyzing safety of industrial systems, such as transportation networks or fixed industrial facilities. The present paper discusses the commonly used QRA techniques and provides a review of measures of risk acceptability. Particular emphasis is given to the fundamentals of quantifying risks near transportation corridors, which are linear risk sources as opposed to the more familiar fixed point sources of risk. The methods are demonstrated through a real life example: assessment of risks due to rail transportation of dangerous goods in the Greater Toronto Area. Where appropriate, comparisons are made with recent transportation routing literature. Recommendations are provided for further research.