Railway Track & Structures - October 2007 - (Page 41)

under the more general track-causedderailment category of Roadbed, is that of track buckling. Track buckling, the sudden lateral movement of the track due to thermally-generated longitudinal rail forces, remains a major track failure mode both in North America and worldwide with, on average, 34 derailments a year in the U.S. alone, with a FRA-reported cost of more than $11 million annually. Since techniques to monitor the neutral temperature of the rail, and thus predict the onset of buckling by measurement, are very limited and difficult to employ, railroads generally rely on preventive measures to control buckling risk. Recently, a risk-based methodology for the assessment of track buckling potential was developed and implemented into a production analysis model (BuckleRisk model), which identifies high-risk track buckling sites by using site-specific risk factors to develop a siterisk value. Based on the magnitude of this value, the potential for a track buckle occurring at the site is defined and the need for any follow-up action identified. In a recent full-system application on a U.S. Class 1 railroad, 24,200 track miles were analyzed, divided into 133,012 segments, with an average segment length of 0.18 mile. The resulting risk analysis identified 30 segments (0.02 percent of system) considered very high risk and an additional 961 segments (0.72 percent of system) considered high buckling risk. The 30 very-high-risk segments were inspected by local forces with immediate follow-up action (destressing) taken at nine of the 30 segments (30 percent), Figure 4. division or railway system. The results have been clear and impressive. Use of risk-based test scheduling techniques reduces the risk of derailments. For example, in the case of broken-rail derailments, use of riskbased assessment and rail test scheduling to determine optimum rail test intervals, has resulted in a reduction in the rate of broken rails and broken-rail derailments by 30 percent or more. Likewise, full-scale applications of the buckling-risk assessment model resulted in a high percentage of highrisk sites identified for immediate action by local forces. 1. Based on paper, “Use of Risk Management in Improving Track Safety,” by Zarembski and Palese, presented at the 2007 AREMA Annual Conference. 2. Federal Railroad Administration, Office of Safety Analysis, Accident/Incident Data. Summary A new generation of track safety management tools has been developed to quantify and analyze the risk associated with key track failure modes. These risk-based assessment tools have been shown to contribute directly to a reduction in track failures through their ability to selectively identify high-risk locations and bring remedial action to bear on these identified locations. The five model classes presented here all rely on research that has been developed over the past several decades, and are designed to be used in largescale applications to identify potential failure sites across an entire route, www.rtands.com Railway Track & Structures October 2007 41 http://www.rtands.com

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Railway Track & Structures - October 2007 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Crossties by the Billions Provide Essentials for Full Support Modern Tools Manage Risk M/W Challenges: Better Management of Thermal Forces in CWR TTCI Celebrates 25 Years as Facility, 10 as Part of AAR Products and Literature People Calendar Sales Representatives Website Directory Advertisers Index Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - October 2007

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