Railway Track & Structures - October 2007 - (Page 40)

Risk management Table 3, above: Sample turnout prioritization. Figure 4, right: High-risk segment report and follow-up action, U.S. Class 1 railroad. to include presence of passenger trains or hazardous materials, importance of the route, speed and density of traffic, etc. Application of this class of model (such as ZETA-TECH’s GeoTest model) to track geometry car data over different U.S. Class 1 railroads showed numerous segments where increased inspection was required, with frequency increasing between six percent and 50 percent, and other segments where decreased inspection frequency was required, with reductions of between 20 percent and 100 percent. The real-time track-geometry interaction approach addresses track-geometry risk issue from a different perspective. It assesses track geometry conditions by going beyond traditional geometry standards and looking at the interaction between the track and vehicle and identifying high-risk locations. This is done using real-time dynamic simulation models such as ZETA-TECH’s TrackSafe model, TTCI’s Performance Based Track Geometry model and AEA’s Real-Time Vampire model. The objective is to identify locations producing unsafe vehicle performance right on the geometry car and provide the railroads with an immediate defect report that will allow them to take fast corrective action. Furthermore, this must be done for a range of simulated speeds and vehicle types. This is illustrated in Figure 3, which shows a rail line that had experi40 Railway Track & Structures October 2007 enced two recent geometry-related derailments. In both cases, a vehicletrack interaction model flagged these locations with “red” roll violations over a range of speeds. In addition, 14 additional locations were also identified on this same line as being likely to produce unsafe response. Prioritization of risk is thus required to determine which of the locations are the most critical. Table 2 presents one such prioritization index from ZETA-TECH’s TrackSafe real-time vehicle-track-interaction model as applied to the high-risk locations. Using this prioritization or risk approach, a railroad has better information about which locations are the most in need of maintenance attention. Turnout condition assessment A third major focus area for track caused derailments is the FRA category of Frogs, Switches and Track Appliances. This category, with approximately 200 to 250 reported derailments per year, addresses turnouts and turnoutcondition-related issues. To this end, switch inspection risk prioritization models have been developed that quantify the inspection-based condition of a switch (turnout), calculate a level of risk and prioritize the need for maintenance or replacement. Using new generation PDA-based inspection tools, such as ZETATECH’s SwitchInspect or ENSCO’s Digital Track Notebook, it is possible to quantify the condition of the turnout using condition measurements made in the field and recorded electronically onto the inspection PDA. This ability of the inspector to record the results of each individual inspection item in numeric form has led to the development of numeric indices for turnouts on a component and system level that can serve as the basis for follow-up maintenance, repair or replacement action. This is illustrated in Table 3, which shows prioritization of switch tamping based on the turnout geometry index values, which would allow for the scheduling of switch tamper activities on a track segment. These indices are in fact risk indices that take into account the criticality of the turnout component and subcomponents, the severity of the condition, and other key information, as provided by the inspection. A key benefit of this index approach is that it provides a consistent and objective method of prioritizing turnout maintenance on a major line segment, region, territory or even systemwide. This is particularly important on a busy rail system where track time is extremely limited and the ability to take a turnout out of service for maintenance or repair is likewise limited. Track-buckling risk management Another high-risk area, which falls www.rtands.com 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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