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Research Results # RR99-01:
Residual Stresses In Railroad Commuter Car Wheels
In the early 1990s, several railroads in the northeast experienced widespread cracking in the wheels of their commuter car fleets. Severe heating of the wheel rim during tread braking was believed to be a contributing factor. FRA initiated a research program to identify the cause(s) and establish remedial actions. This Research Results highlights some of the analysis performed in support of that effort.
A series of calculations were designed to estimate the state of residual stress in railroad commuter car wheels. Predictions of residual stresses in the wheel following manufacture were made by calculating the stress state in the wheel following forming, re-austentitizing, rim quenching and annealing. Model predictions of the effect of the imposition of contact and thermal loads when the wheel is placed in service were completed. After simulated service, the region in the center of the tread would reverse to tension. This condition could lead to the formation and growth of fatigue cracks - or "thermal cracks" - in the rim that could ultimately lead to premature failure of wheels in service.
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Research Results # RR00-01:
Evaluation Of A Top-of-Rail Lubrication System
In pursuit of a common goal of reducing transportation energy consumption, the Federal Railroad Administration (FRA) and the United States Department of Energy (DOE) have participated with the railroad industry in evaluating top-of-rail lubrication systems. These systems apply a consumable lubricant to the top of both rails behind the last locomotive axle to lower the wheel to rail friction of the following cars, thus reducing the energy needed to pull the train. To prevent adverse effects on the locomotive traction of following trains, the lubricant is applied in controlled quantities and it is designed to be consumed as the train passes.
In late February and early March of 1998, the SENTRAEN 2000 top-of-rail (TOR) lubrication system was tested on a 243-mile segment of CSX Transportation (CSX). The testing was jointly sponsored by the FRA's Office of Research and Development, DOE, CSX, and Tranergy Corporation (the TOR developer). CSXT, Tranergy, and ENSCO, under contract from the FRA, designed the tests and analyzed the data.
An average fuel savings of 7.7% was achieved in tests of a top-of-rail lubricant and application system on CSX between Corbin, KY and Cartersville, GA. The test measurements were made during six round trips of a typical 90-car coal unit train. No adverse effects on braking or train handling were observed during the tests.
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Research Results # RR00-02:
Developed Wheel And Axle Assembly Monitoring System To Improve Passenger Train Safety
To encourage the expansion of safe high-speed passenger rail service nationwide, the FRA sponsored the development and testing of two autonomous systems to monitor passenger trains to help ensure safety and ride quality. This monitoring is essential for high-speed trains where the consequences of derailment are potentially greater than for trains traveling at lower speeds. The first system is a rugged unit that can function reliably in extreme environments. This system was tested on a Talgo train with tilting technology traveling between Portland and Vancouver during the summer and fall of 1998. The unit was installed to monitor Talgo's compliance with an FRA waiver allowing the train to travel through certain curves at speeds higher than those of a non-tilting train.
The second system is a lighter less rugged system designed for passenger cars where the operating environment is typically less harsh than that of locomotives. The system was installed on Amtrak passenger cars traveling from Bakersfield to Sacramento California and from Washington, DC to New York City. This unit was designed to measure and monitor the vibration of wheel and axle assemblies using standard accelerometers. The measurements were then processed using a neural net computer that "learns" in a manner similar to a human. The data can be used to identify track and vehicle maintenance and repair needs and potentially unsafe conditions.
The tests successfully demonstrated that the remote monitoring systems could provide a reliable means for detecting potentially unsafe track and vehicle conditions in near-real time. In addition it can be easily modified to meet various users' monitoring requirements.
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Research Results # RR00-03:
Analysis of Antennas to Improve Differential Global Positioning System (DGPS) Reception on Locomotives
The Federal Railroad Administration (FRA) Office of Research and Development sponsored a research investigation to improve DGPS signal reception in the locomotive electromagnetic interference (EMI) environment. The main objective of this investigation was to test whether a new Starlink prototype E-field antenna designed to significantly reduce EMI effects surrounding operating AC and DC locomotives performed as intended.
During the testing, the performance of the Starlink prototype balanced E-field cone antenna was compared to that of a standard off-the-shelf Starlink H-field loop antenna (MBA2). The antennas were placed in various locations on the roof of the test locomotives. Overall, the Starlink E-field cone antenna performed significantly better than the off-the-shelf Starlink H-field loop antenna, increasing the signal-to-noise ratio (SNR) by 10 dB. It was determined by prior tests that a 10 dB increase in the SNR is sufficient for the Nationwide Differential Global Positioning System (NDGPS) Service to work effectively on railroads. The NDGPS Service will broadcast differential correctors for GPS throughout the nation on the radio beacon band 285 kHz - 325 kHz.
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Research Results # RR00-04:
Computer Model Developed To Predict Rail Passenger Car Response To Track Geometry
The Federal Railroad Administration sponsored research to develop a computer model to predict the interaction between vehicle and track as a railroad passenger car travels over track with known geometry. This computer model is capable of identifying potentially hazardous sections of track when given the track geometry and the vehicle speed. These predictions will improve safety of railroad operations by helping to determine the maintenance needs for tracks.
This computer model, known as a neural network system, estimates the vertical and lateral forces on the wheel/rail interface as a function of the geometry of the track and the operating characteristics of the vehicle. Unlike conventional computer models, a neural network simulates the analytical workings of the human brain. A series of computer models of a railroad passenger car were developed to evaluate the effectiveness of the neural network. This series of computer models accurately represents the dynamic response of an actual railroad passenger car. The neural network output closely predicts the series of computer models. In the future, the fully developed system will be used to identify track locations where the estimated lateral and vertical forces exceed the limits recommended for safe operations. Only the track geometry and train speed, which are routinely and easily measured parameters, need to be known in order to identify the potentially hazardous locations.
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Research Results # RR00-05:
Instrumented Wheelset System Results Verified The High Speed Safety Standards
To improve the safety of high-speed passenger coaches, the Federal Railroad Administration sponsored research to develop an instrumented wheelset system that collects wheel/rail forces and acceleration data on a high-speed passenger coach and then compares vehicle performance with newly adapted vehicle track interaction (VTI) safety limits. Data was collected over a 450-mile round-trip route on the Northeast Corridor (NEC) between Washington, DC, and New York City. This data was then compared to the VTI limits in the High-Speed Safety Standards to verify that the passenger coach ran under safe conditions.
The completed tests demonstrated that the instrumented wheelset system accurately measures wheel forces and accelerations. A VTI exception report showed that there were no exceptions to the VTI safety limits specified in the standards for high-speed track safety on NEC throughout these tasks.
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Research Results # RR00-06:
Fractal Analysis Of Geometry Data For Railroad Track Condition Assessment
The Federal Railroad Administration sponsored a research project to investigate the application of Fractal Analysis to railway track geometry data and to develop numerical indices based on this analysis for use in track condition assessment, improved safety and efficiency of operations, and diagnosis of the cause of poor track condition.
Fractal Analysis is an analytical technique that can be applied to characterize and to quantify irregular patterns that are chaotic and random; as track geometry data are classified. Fractal analysis of geometry data revealed that the mid-chord offsets (MCOs) of the vertical profile data have typically two orders of roughness. This bi-fractal condition results in three fractal parameters to describe the geometry pattern: two independent fractal dimensions (DR1 and DR2) based on the slope of the log-log plots and the location of the breakpoint.
Two fractal analysis software programs were developed during this research: (1) Fractal Track Evaluation (FTEval) used to evaluate the applicability of fractal analysis to track geometry, and (2) Fractal Track Automatic (FTAuto), evolved from the FTEval, which performs fractal analysis on the geometry data for any length of track. The study concluded that the geometric patterns of the track conditions could be studied through fractal analysis.
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Research Results # RR01-01:
FRA's High Speed Research Car, T-16
In November, 2000, the Federal Railroad Administration (FRA) began operating high speed research car T-16 (Figure 1) to investigate methods for providing a safer and smoother ride for passenger and freight trains traveling at higher speeds. FRA's Office of Research and Development uses T-16 to study the dynamics of wheel-rail behavior, to investigate methods for improving track inspection, and to assess potential high speed rail corridors. T-16 also assists Amtrak, local and regional commuter authorities, and individual railroads in assessing their routes.
T-16 is a former Amtrak Metroliner passenger car that was refurbished and instrumented with advanced technology, with capabilities for measurement and data collection at speeds up to 160 mph. Measurement capabilities include track geometry, rail head profile, ride quality, and wheel-rail forces.
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Research Results # RR02-01:
An Examination of Railroad Yard Worker Safety
To assist the U.S. railroad industry in its efforts to improve safety, the Federal Railroad Administration (FRA) Office of Research and Development's Human Factors Program sponsored an exploratory study into causes and contributors to railroad yard injuries and human factor-attributed train accidents. Part of this research involved analyses of large FRA-maintained databases of injury and accident data, while another part involved structured interviews with rail management and focus groups with rail labor. Based on the findings from the large database analyses and structured interviews and focus groups with rail management and labor, a number of recommendations were made to increase safety in railroad yards. Recommendations focused on activities that both the railroad industry and the FRA can do to achieve a safer workplace.
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Research Results # RR02-02:
A Preliminary Examination of Railroad Dispatcher Workload, Stress, and Fatigue
Railroad dispatchers play a critical role in the safe operation of the nation’s railroads. In response to concerns raised by two Federal Railroad Administration (FRA) safety audits of dispatching operations in the U.S., FRA’s Office of Research and Development undertook a study to examine levels of workload, stress and fatigue in the railroad dispatching environment. A field study at two dispatching operations, one freight and one passenger, provided data for this analysis. Data collected in the field included physiological measures as well as self-report data, third party observation and paper records. The results of this study include findings with respect to dispatcher characteristics and their work environment as well as levels of workload, stress, and fatigue.
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Research Results # RR02-03:
Ground Penetrating Radar for Railway Track Substructure Investigation
The Federal Railroad Administration (FRA) Office of Research and Development's Track and Structures Program sponsored a study for evaluating railway track conditions. Ground Penetrating Radar (GPR) can provide a rapid, non-destructive measurement technique for evaluating railway track substructure integrity. This is being proven in an ongoing study to develop GPR for defining the condition of the railway substructure. Examples of the results of the GPR project to date are shown in Figures 1 & 2. The scan in Figure 1 shows the varying thicknesses of ballast and subballast which, in this example, is an indication of a problem associated with lateral subballast spreading on top of a clay subgrade. The scan in Figure 2 shows ballast pockets that have developed under the track. GPR provides continuous top-of-rail measurements of substructure layer conditions, with the potential to measure the layer thickness, water content, and density of the substructure components (ballast, subballast, subgrade). GPR is also capable of observing trapped water from poor drainage, soft subgrade from high water content, and is potentially capable of distinguishing fouled ballast from clean ballast. The study concluded that GPR images can give a good indication of the subsurface layer configuration and patterns within the data can give a good indication of subsurface condition.
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Research Results # RR03-01:
The Influence of Track Maintenance on the Lateral Resistance of Concrete Tie Track
Amtrak and the Federal Railroad Administration (FRA) jointly sponsored tests to measure and document the influence of track surfacing, DTS, and to a limited extent - traffic, on the lateral resistance of concrete tie track. During the tests, the DTS stabilized three different test sections at operating speeds of 0.7, 1.5, and 2.0 mph, respectively - all within the manufacturer's recommended range. Results indicated that surfacing (tamping) reduced the lateral track resistance to a range of about 52% to 63% of its initial level. DTS operation restored from 24% to 37% of the lateral resistance lost from surfacing, while the traffic passage of 3,360 gross tons (0.00336 MGT) restored about 13% of the lost resistance. Within the tested operating speed range, no clear variation in DTS effectiveness was evident.
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Research Results # RR03-02:
Passenger Train Fire Safety
Heat release rate (HRR) has been recently identified as a key indicator of real-scale fire performance of a material or construction, as well as ignition, flammability, and smoke emission. In 1994, the Federal Railroad Administration (FRA) began a multi-phase research study to investigate the use of fire hazard assessment using HRR data to provide a more credible and cost-effective means to predict the actual fire behavior of passenger train materials. HRR-based fire performance data for 30 materials used in typical Amtrak intercity rail cars were obtained from the conduct of Cone Calorimeter tests. The Cone Calorimeter test data and data from current FRA-cited test methods were compared. For the majority of materials, the relative ranking from “best” to “worst” was similar in both test methods.
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Research Results # RR03-03:
The Impact of Safety Rules Revisions on Safety Culture, Incident Rates, and Liability Claims in the U.S. Railroad Industry: A Summary of Lessons-Learned
The Federal Railroad Administration (FRA) Human Factors Research and Development (R&D) Program sponsored a lessons-learned study to examine the impact of safety rules revision on safety culture, incident rates, and liability claims in the railroad industry. Safety rules revision (or rules consolidation) identifies key rules that are universally enforceable and eliminates unnecessary and conflicting rules. The process also seeks to promote improvements in safety culture through labor-management collaboration in the rule revision. Thus, it involves a shift in primary responsibility for rules creation from management to front-line workers with management in a support role.
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Research Results # RR03-04:
Locomotive Crew Egress
Locomotive operating crews and rescue workers need improved means of cab egress and access in the event of an accident. Although present regulations and practices address this need in a limited way, further measures could provide substantial improvements in the survivability of crews. The purpose of the first phase of this program was to conduct a multi-faceted assessment of egress options in current locomotives, assess some accident conditions that crews could face, and suggest the most productive improvements. The assessment involved review of existing regulations, site visits to commuter and freight railroads, and interviews with train crews. A review of National Transportation Safety Board (NTSB) accident investigation reports and the FRA accident/incident database identified accident scenarios where lack of adequate egress was an issue. Computer simulation of locomotive crash scenarios identified structural areas of the cab structure that could be improved for better egress, and also established the severity of the effects on crews. Based on the findings of the first phase of the program, subsequent work focused on development of an innovative crew egress system for rollover derailment accidents. Options for crew egress are most limited in this situation. Three design concepts were evaluated with train and engine crewmembers and emergency rescue personnel. A mockup of the most promising concept, a roof-mounted escape hatch, provided the means for a preliminary evaluation of the usability of the hatch system. Test subjects were able to actuate the hatch and escape the cab in 30 seconds or less. Future work will involve refining the hatch design so that it is easily manufactured and exploring secondary egress options.
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Research Results # RR03-05:
Locomotive Fuel Tank Safety
In a continuing effort to improve rail safety, reduce the number of injuries and fatalities to rail workers and reduce the impact of train accidents on the environment, the Federal Railroad Administration, the Association of American Railroads and the locomotive builders have worked cooperatively to review the performance and design of locomotive fuel tanks. The FRA undertook this project to further advance understanding of the performance of locomotive fuel tanks and to identify opportunities for further improvement to enhance their crashworthiness. A finite element model of a “generic” fuel tank was the basis for the analysis of three static crash scenarios and one dynamic loading case. Results of these analyses illustrate the power of this approach in determining the contribution of alternative design changes to fuel tank crashworthiness. The results also suggest several practical and cost-effective design improvements.
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Research Results # RR03-06:
Human Reliability Analysis in Support of Risk Assessment for Positive Train Control
This report describes an approach to evaluating the reliability of human actions modeled in a probabilistic risk assessment of train control operations. Human reliability analysis was applied to a safety evaluation of the Communications-Based Train Management System (CBTM) being tested by CSX Transportation, Inc.
The study analyzed the probabilities of specific human errors representing potential contributors to the risks being modeled in a risk analysis study of the CBTM system for four train related events: entering a block without authorization, exceeding the track speed limit, entering a preplanned work zone without authorization, and crossing a misaligned switch. Figure 1 shows the two error distributions based upon experience on CBTM territory only and all CSXT territory for trains entering a block without authorization.
The distributions were created using a combination of objective and subjective sources. The report also includes a set of guidelines and recommendations for performing a human reliability analysis to insure that the results will be acceptable to the broad set of stakeholders, meet accepted standards for human reliability analysis, and able to be integrated into probabilistic risk assessments.
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Research Results # RR03-07:
Human Aerodynamic Effects of High-Speed Trains
With the onset of high-speed train operations in the United States, a study was undertaken to determine the possible aerodynamic effects of these trains have on their surroundings. The aerodynamic interaction between a high-speed train passing other trains, and its effects on the structural integrity of window mounts and glazing as well as the stability of large lightweight empty container cars operating on adjacent tracks (Figure 1) were analyzed. Although car-body roll of container car was not significant, the analysis indicates that the potential for derailment was greatest for cars with empty containers, while wheel lift was eliminated and the lateral to vertical wheel/rail forces (L/V) were much lower when all containers were fully loaded. Another area of investigation focused on the effects of aerodynamic pressure and airflow generated from high-speed trains to people standing on the passing station platform. Computational fluid dynamics analysis, rail dynamics simulation models, and field measurements using pitot tubes and aerodynamic dummies developed by the French National Railways (SNCF) were used to study these effects. Preliminary results show the aerodynamic effect of an Acela Express at 150 mph is less than that of a conventional train at 125 mph.
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Research Results # RR05-01:
Development of Objective Track Quality Indices
The Federal Railroad Administration (FRA) Office of Research and Development initiated a research project to develop a set of objective track quality indices (TQI) from track geometry data to assess track conditions in supplementary to the existing Federal Track Safety Standards. Through its Research and Development programs on the high-speed research car (T-16) and the Automated Track Inspection Program (ATIP), a large amount of track geometry data was collected between 2000 and 2002. The data portrayed a comprehensive picture of condition of the nation's rail network.
The basic concept is the use space curve length to represent track quality. Space curves are generated by track geometry measurement systems on a foot-by-foot basis. As illustrated in Figure 1, for a specified track segment length, the rougher the track surface, the longer the space curve will be when stretched into a straight line. A large number of track geometry surveys were processed and analyzed. The results show that the new FRA TQIs can quantitatively describe the relative condition of track surface geometries. Furthermore, the new TQIs are found to correlate well with the FTSS (Federal Track Safety Standards) for each track class. TQI results for different track classes were fitted to popular distributions. Satisfactory results are achieved.
