HAZARDOUS MATYERIALS CAR PLACEMENT IN A TRAIN CONSIST. VOLUME I: REVIEW AND ANALYSIS

In response to major derailments involving hazardous materials cars, the Federal Railroad Administration (FRA) initiated this review of the consequences of hazardous materials car placement in a train consist. The review and analysis consisted of six task items: (1) review of accident trends and regulations, (2) an analysis of hazardous materials compatibility, (3) railroad operational constraints, (4) a cost/benefit analysis, (5) recommendations, and (6) preparation of a final report. A review of the 1982-1985 Railroad Accident/ Incident Reporting System (RAIRS) data showed the rear quarter to be statistically the "safest" location in a mainline freight train. Analysis confirmed that the longer the train, or the higher the speed, the more cars derailed on the average. Also, the top 101 hazardous commodities (by volume movement) plus fuming nitric acid were analyzed for chemical incompatibility, a total of 5,151 binary combinations. Of these, 1,210 combinations were judged incompatible. Combinations involving nonoxidizing mineral acids (ASTM Chemical Reactivity Group I ), oxidizing mineral acids (Group 2) and caustics (Group 10) dominate the list of incompatible chemicals. Consequence-based and risk-based rankings were established. Calculations established a post-derailment separation distance of 40 meters minimum to prevent mixing of incompatible chemicals. This can be accomplished by a conservative (worst-case) in-train separation by 30 cars for incompatible hazmat cargos, although a 15-car separation may accomplish this for most accident scenarios. It was noted that mixing of hazmat materials was not cited in any NTSB accident report as a specific problem.