Reply: Establishing derailment profiles by position for corridor shipments of dangerous goods

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  • 194 CAN. J. CIV. ENG. VOL. 19, 1992

    the portion where dynamic excitation is fully developed, the safest location in a train for cars with dangerous lading must tend to be in the leading portion, immediately behind the 6th car behind the locomotive (to safeguard crew members). Such marshalling is not always operationally feasible and the 1982 regulation quoted by the authors recognizes this, while imposing various specific restrictions. Although the quantity of dangerous goods moved by rail has been increas- ing, most trains do not derail and those that do seldom result

    in a significant dangerous goods release. For example, during 1984 there were 230 derailments of through trains. Of these, 56 (24.3%) had dangerous goods cars involved, and in only one case was a significant release of cargo (sulphuric acid) involved.

    The conclusions drawn by the authors tend, therefore, to be somewhat irrelevant to the practical considerations involved.

    Establishing derailment profiles by position for corridor shipments of dangerous goods: ' Reply

    F. F. SACCOMANNO Department of Civil Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3Gl

    AND

    S. M. EL-HAGE Transportation, City of Brampton, Brampton, Ont., Canada

    Received July 22, 1991

    Manuscript accepted July 22, 1991

    I I Can. J. Civ. Eng. 19, 194-195 (1992)

    ~ Mr. Cruden raises a number of valid points concerning I the Canadian Transport Commission (CTC) rail accident I

    data base and the need to consider track structural failure and dynamics in assessing train derailments. Many of his comments, however, touch on issues that are well beyond the scope and intent of our study.

    In our paper, we attempted to show that the potential derailment of railcars carrying dangerous goods is affected by their position along the train consist. As a result, effective marshalling to positions with the lowest derailment potential can enhance the overall safety of transporting dangerous goods by rail. Observations taken from the 1983-1985 CTC rail accident data base suggested that involvement of railcars in derailments depends primarily on two factors: (1) the point at which derailment is initiated, and (2) the number of cars involved. The number of cars involved in a derail- ment block was found to depend on the train operating speed and on the cause of derailment. A similar relationship was suggested in the 1983 A.D. Little Inc. study of train derailments in the United States (referenced in the paper).

    I A statistical analysis of the CTC accident data indicated that the point of derailment along the train depends primarily on the cause of derailment (Table 3 in the paper). For "track-related failures" (i.e., roadbed defects, rail and joint bar failures, and switch defects), a significant share of derailments took place within the first 10% section from

    is cuss ion by J.M. Cruden. 1992. Canadian Journal of Civil Engineering, 19: this issue. Pnnlcd In Canada / Irnpr~rnc au Canada

    the front of the train. Track-related derailments represented over 45% of all derailments in the CTC data base (Table 6 in the paper). Even considering all causes together,'the first 10% section of train length reflected over 10% of all derail- ments in the data base. From these results, it is difficult to accept Mr. Cruden's assertion that the safest position for railcars carrying dangerous goods is at the 6th position from the front of the train for all track conditions and derailment causes. Such an assertion does not appear to be supported by the available data, especially when track-related causes are being considered.

    We cannot comment on Mr. Cruden's assertion that the U.S. Federal Railwav Association (FRA) cause codes do not adequately reflect track structural faiures causing train derailments. The U.S. FRA coding scheme includes an extensive list of failure possibilities. Our study was based on a highly aggregated representation of the U.S. FRA cause codes for the purpose of explaining derailment potential according to position and cause. The assumption is that a train derailment has already taken place. It was not our intention to use these cause codes to reconstruct at the micro level the accident failure process for the purpose of assigning fault.

    Mr. Cruden is correct in suggesting that practical con- siderations require that regulations governing the placement of dangerous goods railcars be applied on a system-wide basis. However, this does not deny the fact that certain corridor features have a significant effect of the point of derailment and should be considered in assessing the pre-

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  • DISCUSSIONS 195

    ferred placement of dangerous goods cars. The question is how best to achieve this objective without incurring unrealistic procedural problems or high operational costs. In our paper, the practicability of a system-wide marshalling strategy was not discussed. We did suggest, however, that such a regulatory strategy fails to reflect unique corridor features affecting derailment potential for different positions along the train.

    Current regulations governing the rail transport of dan- gerous goods reflect some fairly significant operating costs. The railways have argued that they are not justified with

    regard to risk reduction for the rail transport of dangerous goods. In the paper, we argue that some costly regulations could be relaxed if effective marshalling strategies were adopted that produce fewer dangerous goods derailments. Significant savings could be realized by the railways without incurring higher risks. Our paper demonstrates this with reference to train speed reductions, and their effect on reduc- ing derailments by position. Effective marshalling could be substituted for more costly speed reduction strategies resulting in the same derailment profiles for dangerous goods cars along a given railway corridor.

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