| A quantitative risk model is presented that estimates the probabilities and consequences of hazardous material transportation spills in the urbanized portion of Calcasieu Parish, Louisiana, a major oil refining and petrochemical manufacturing center with a heavy hazardous material transit. A BASIC language computer program incorporates spilling event probabilities, impact zone calculations, and local day/night population densities to estimate relative risks. The only consequences considered are acute harm to persons--injuries and fatalities as an immediate result of a spill. Long-term human or wildlife/ecological impacts are excluded.;Major transportation routes in the study area are segmented and detailed hazardous material flow estimates by type and quantity are used to calculate spills risk by mode, material, materials by mode, and segment. On each segment, each significant or representative material is modeled for several discrete spill sizes and various weather conditions. Each event scenario is assigned a separate probability and consequence. Consequences are numbers of persons harmed, the product of impact area and population density. Comparative risks are expressed as expected loss and as a risk spectrum.;Model and probability estimation inaccuracies make the study's risk results valid only in relative, not absolute, terms. In terms of expected loss, the highway mode has the greatest risk, followed by water and rail. The material posing the highest risk is ammonia. Hazardous waste spills have a near-zero acute risk. A modeled rerouting of highway hazardous material on an interstate bypass increased expected loss. Segment risk and risk by distance from the transportation route are also presented. |
