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Title:Quantitative analyses of unit train safety and railroad tank car implementation policy
Author(s):Li, Weixi
Advisor(s):Barkan, Christopher P.L.
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Unit Train Safety
Manifest Train Safety
Tank Car
Tank Car Implementation Policy
Loading Condition
Safer Tank Cars
Train Configuration
Phase-in Schedule
Abstract:Railroads play a critical role in the transportation and economic prosperity of North America. Train safety has improved considerably over the past decade. However, with the large volume of traffic, accidents still occur. Derailments are the most common type of train accident recorded in the Federal Railroad Administration’s Rail Equipment Accident/Incident database. The research presented in this thesis focuses on derailments and releases of hazardous materials, specifically three topics related to this general theme: unit train loading condition, the effect of train configuration on risk, and policies for implementation schedule for safer tank cars. The effect of loading condition on unit-train derailment occurrence, causes and severity is described in Chapter 2. An algorithm was developed to identify derailments of loaded and empty unit trains on mainlines and sidings recorded in the Federal Railroad Administration database. A dataset of these accidents for the 15-year period from 2001 to 2015 was developed and analyzed. The frequency of derailments for both loaded and empty unit trains declined by more than 50%. The average number of cars derailed per accident fluctuated for both loading conditions but showed no particular trend. Approximately five times more loaded unit train derailments were recorded than empty unit trains but in the absence of specific unit train traffic data, inferences about rates are not possible. Loaded unit trains were more than four times heavier than empty unit trains, and loaded train derailments tended to involve more cars than empty train derailments. The distribution of derailment causes differed for loaded and empty unit trains. Loaded trains most frequently derailed due to broken rails and welds, while the leading cause of empty train derailments was obstructions, which included severe weather. Over 90% of the derailments of loaded and empty unit trains considered in this study occurred on mainline tracks, and the distribution of causes differed between mainline and siding tracks. Chapter 3 presents an analysis of the risk associated with transporting hazardous materials by unit trains versus manifest trains. While unit trains offer efficient transportation of hazardous materials, if these trains derail, the consequences can be particularly severe. Transporting hazardous materials in unit trains reduces exposure to accidents compared to transporting the same quantity of material in a larger number of manifest trains. However, in the event that a derailment of a unit train does occur, the consequences may be greater. Conversely, transportation in a larger number of manifest trains increases the exposure to derailments, but may reduce the severity if an accident occurs. An investigation of these trade-offs using the Multiple Tank Car Release model to conduct a series of simulations is presented. As part of this analysis the effect of using DOT 111 tank cars was compared to use of DOT 117 tank cars. Both the likelihood and consequence of transporting hazardous materials in these different train configurations were estimated and the metrics used to estimate risk were the distributions of number of tank cars derailed, number of tank cars releasing, and quantity released. Use of safer tank car specifications can substantially reduce the consequences and risk of derailments involving hazardous materials. Nevertheless, there are practical and financial considerations associated with replacing the existing fleet with new cars. Safer tank cars are generally more expensive to build and operate, and there may be practical constraints due to manufacturing capacity. In the late 2000s, the government and industry were faced with a choice of immediate adoption of a safer tank car for Toxic Inhalation Hazard materials, or awaiting the results of a research and development project to develop an even safer car. The discussion between the government and industry regarding phase-in policies for safer tank cars led to the research described in Chapter 4. Specifically, how would different policies regarding deferral of the decision to implement safer cars, and the schedule of replacement affect risk. In Chapter 4, a methodology is presented to quantify the risk associated with rail transport of the top two toxic inhalation hazard materials by shipment, ammonia and chlorine. A network risk analysis model was used in conjunction with routing information, population, and the Multiple Tank Car Release model to estimate several risk metrics under different implementation scenarios.
Issue Date:2018-04-26
Type:Thesis
URI:http://hdl.handle.net/2142/101380
Rights Information:Copyright 2018 Weixi Li
Date Available in IDEALS:2018-09-04
Date Deposited:2018-05


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