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82 Hazardous Materials Transportation Incident Data for Root Cause Analysis ing their journeys, most failing components are indeed found before they cause a problem, but a few are missed and these sometimes result in an accident. Each of the railcars in the train is subject to dozens of different failure modes with the poten- tial to cause an accident. Although terminal personnel and the train crew are responsible for inspecting key attributes of the cars before departure and at certain intervals during a journey, many problems are difficult to detect or can become critical en route. The nature of trains is that crew members are separated from most vehicles by a considerable distance and will often be unaware of an incipient failure until it has already occurred. Consequently, railcars are necessarily robust and, wherever possible, designed in a fail-safe manner. As mentioned above, railcars undergo human inspection in terminals and, in addition, railroads rely heavily on a variety of automated technologies to detect certain types of vehicle failure. The industry is aggressively developing new technologies to expand this capability to other components and failure modes. Overall, FRA has more than 140 different cause codes for railroad-equipment-caused accidents. 4.6.4 Train Operation--Human Factors Accidents caused by human-factors rank third among the major accident categories in terms of frequency but second in terms of causing hazmat releases. The majority of these are accidents in yards and industry tracks, although mainline collisions are a particularly important cause for the reasons discussed below. Human-factors accidents vary widely in their severity and poten- tial to cause serious hazmat releases. Among the most common human-factors-caused accidents are various errors committed during switching, such as run through switches. These are gener- ally low-speed incidents with little potential to cause sufficient damage to a hazmat car to pro- duce a serious release. On the other hand, accidents caused by failure to obey signals on the main- line or other operating instructions can result in high-speed collisions with substantial potential to breach one or more hazmat cars. Several of the most serious hazmat release accidents in the past few years have been due to such failures. Both FRA and NTSB have placed a high priority on developing technology and implementing requirements for adoption that are intended to prevent certain types of human-factors accidents from happening. Notable among these is the recent rulemaking requiring implementation of Positive Train Control (PTC) on all rail lines handling toxic inhalation hazard (TIH) materials. 4.6.5 Summary of Causes and Impact The points discussed are pertinent to the root cause analysis objectives of this project because there are a wide variety of possible causes, any one of which occurs relatively infrequently. These incidents are distributed over 150,000 miles of railroad lines and 1.5 million freight cars. Con- sequently, the rate of failure for any particular component or system is relatively low and dis- persed across a large system. In order to understand the principal factors most likely to result in conditions that can lead to a hazmat release, a statistical approach is needed. In the context of understanding the contribution of the current FRA Guide for Preparing Accident/Incident Reports (FRA 2003) to root cause analysis, it is worth reviewing a few of the cat- egories that railroads are required to provide: Item 38--Primary Cause Code, Item 39--Contribut- ing Cause Code, and Item 52--Narrative Description. Item 38--Primary Cause Code Proper entry of the correct primary cause code is of critical importance, not only for the accident being reported, but also for FRA's analyses conducted for accident prevention

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Database Analysis 83 purposes. Because of the extensive use made of primary cause code entries, careful attention must be given to making correct entry for all accidents. (FRA 2003a, p 11) As stated by FRA, this code is critically important to "accident prevention analysis," which is implicit in root cause analysis. There are several additional paragraphs providing more detail about the factors railroads should consider when identifying and possibly updating the Primary Cause Code as more information becomes available. Item 39--Contributing Cause Code If there were one or more contributing causes, enter the code for the foremost contributing cause. Otherwise, enter "N/A." An accident is frequently the culmination of a sequence of related events, and a variety of conditions or circumstances may contribute to its occurrence. A complete record of all of these would be beneficial in accident prevention analysis. However, it is not practical, even if it were possible, to develop forms and codes that would capture every detail that may be associated with the causes and resulting consequences of each accident. Therefore, the most appropriate combination of available codes that best identifies the likely primary and any contributing cause, and other factors, is to be used. Railroads are encouraged to use the Contributing Cause Code. When the events cannot be adequately describe[d] using the Primary and Contributing Cause, the railroad must use the Narrative Block to complete the causes of the accident. (FRA 2003a, p 13) As discussed in this report, accidents are often the result of more than one factor. FRA explic- itly recognizes this elsewhere in their discussion of the accident reporting and analysis process and, by providing Item 39--Contributing Cause Factor, they allow for one contributing cause to be identified. In the context of root cause analysis, this may be one area for improvement. FRA states that more than one contributing cause may be a factor and asks the railroad to enter the "foremost contributing cause," implying that only one be identified. It seems feasible that the process could be modified to allow for multiple (perhaps up to three) contributing causes to be identified, with a requirement that they be rank-ordered in importance (i.e., Contributing Cause 1, 2, and 3). However, this would often require a certain amount of subjectivity in ranking the causes and different individuals or railroads might use different criteria, thereby introducing additional variability. Furthermore, the notion of primary and contributing causes may have a tendency to over-simplify the process. It may be worthwhile to consider proximate and ultimate causes with more sophistication. Another potential measure could be to evaluate whether this aspect of the reporting system can be modified to enhance the value of the information. In recognition of the potential complexity of factors contributing to an accident, FRA requires that railroads provide additional details in Item 52--Narrative Description. FRA's general instructions are as follows (FRA 2003a, p 15): A detailed narrative is basic to FRA's understanding of the factors leading to, and the consequences aris- ing from, an accident. While many minor accidents can be described in a few brief comments, others are more complicated and require further clarification. In addition, FRA specifically requests that information be provided on drug/alcohol involve- ment, cause, diesel fuel tank, hazardous materials, and other railroads. Of these, the following are of particular relevance to hazmat root cause analysis and the text for each is as follows (FRA 2003a, pp 1516): Drug/alcohol involvement--Include a discussion of any drug/alcohol use connected with this accident. If positive tests were made, but usage/impairment was not determined to be a causal factor, explain the basis of this determination. Cause--Discuss any event(s) or circumstance(s) occurring prior to the accident that has relevance to the accident. Provide additional information concerning the reasons(s) for the accident when the causes found in Appendix C do not sufficiently explain why the accident occurred. Hazardous Materials--Identify the initial and number of any car releasing hazardous material. List the name and indicate the quantity of hazardous material released. Report the number of fatalities and injuries resulting from a direct exposure to the released substance. If there was an evacuation, estimate the size of the affected area and the length of the evacuation.