Using geographic information systems to assess the risks of hazardous materials transport in networks

Routing hazardous materials (hazmat) wisely, and designing safer networks for doing so, are powerful means to reduce the potential negative impacts of transporting them. A fundamental requirement of route design and assignment is to assess the potential risk imposed by shipments traversing each link in a network. We consider the risks imposed on human populations by airborne contaminants (such as ammonia and chlorine), modelling their dispersion using a Gaussian Plume model. We model the probability of an undesirable consequence (such as injury, illness, or death) as a function of contaminant concentration. We then apply an expected consequence approach, whereby risk is treated as the product of this probability and the population affected. Map algebra techniques, from Geographic Information Systems (GIS), allow us to combine concentration mathematically with the population distribution to estimate risk, for a release at any point on a network, for all parts of the study area. Map algebra further allows us to apply these risk estimates to every link in the network.