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1 Transit systems have significant infrastructure, including rail. As rail track ages and more and more traffic passes over the railâthat is, as the rail accumulates trafficârisk of failure increases, which in turn increases the risk of derailments and other catastrophic events. To detect internal defects, most transit agencies use ultrasonic testing (UT) as the primary method of inspecting rail. UT is further supplemented with track circuit detection of broken rails and visual inspection, although those methods are mostly used for detecting rail breaks, external surface flaws, and surface defects. Once an internal defect is found, the section of rail that contains the defect is usually replaced. The frequency of UT inspection is driven by a number of factors, including age of the rail, the amount of traffic (and axle load), environmental conditions, track support condi- tions, and location and characteristics of the rail. Most transit agencies use experience and traditional regulatory guidelines for scheduling inspections and UT. However, risk-based UT scheduling, which has been recently introduced and is now incorporated into the FRA track safety standards, is not commonly used or even widely understood. Furthermore, the transit industry does not currently have a uniform methodology for scheduling rail inspec- tions to detect rail flaws. The objective of this synthesis is to document the current state of transit system practices for rail inspection and maintenance as they relate to preventing rail breaks and derailments. This study consisted of a comprehensive survey, in the form of a questionnaire, sent to 28 heavy- and light-rail transit agencies. Of those agencies, 16 responded, including seven of the 10 largest heavy-rail transit systems, accounting for approximately 80% of the heavy-rail transit miles in the United States. Seven of the top 10 light-rail transit systems also responded. In addition, three transit systems were identified, on the basis of the survey results, to serve as in-depth case examples. This report presents the results of the survey and analysis of the response data in an effort to synthesize current practices. The results indicate that the occurrence of rail defects, broken rails, and broken rail derailments is consistent with the rate of development found in other studies that look at larger populations of rail defects. Likewise, the larger and more heavily used transit systems develop increased levels of defects, which is again consistent with what is seen in the railroad industry at large. There is no consistency, however, in the use of UT and other rail testing techniques. Larger transit systems conduct UT testing at higher frequencies. Smaller transit agencies rely more heavily on visual inspection and track circuits, with a minimum level of UT testing. Although track inspectors are often skilled at finding surface defects, they cannot spot internal defects, which represent the highest-risk defect type; such defects often grow to failure with no visible indication until they fracture (break), with the potential to cause a derailment. Thus, as these systems S U M M A R Y Maintenance Planning for Rail Asset Managementâ Current Practices
2 Maintenance Planning for Rail Asset ManagementâCurrent Practices age, and as the rail accumulates more traffic, they are expected to develop greater numbers of internal rail defects that will require a more aggressive UT program to help minimize the occurrence of broken rails. Likewise, reliance on track circuits to identify broken rails is an effective stopgap, but this method offers no insight into the rate of defect initiation, which increases exponentially with the age of the rail. Because simply scheduling more tests is neither cheap nor sound engineering practice, risk-based scheduling is a potential means of determining how much additional testing should be performedâspecifically, that which could benefit transit systems through both increased safety and minimized costs. On the basis of the survey results, this synthesis developed suggestions for follow-up studies.