The Track and Structures Research Program element covers all aspects of the railroad guideway, including embankments, ballast, ties, fasteners, rail, turnouts, bridges, and tunnels.  It encompasses track geometry measurement, defect detection, and design and maintenance issues. A significant portion of FRA’s Track and Structures Research Program involves a joint effort with three of the AAR’s Strategic Research Initiatives: Track Integrity Monitoring, Bridges, and Track Components.

Why a Priority?

Today, one third of all railroad accidents are attributable to track defects.  Based on FRA’s accident/incident statistics for the five-year period of 1996-2000, an annual average of 943 incidents were attributed to track as a primary cause.

While the track-related accident rate was relatively steady during the 1990's, the reported damage grew significantly, doubling from $55 million in 1993 to $111 million in 2000.  As the reported damage figures only include direct property damage, the full cost of these accidents is estimated to be about 2 to 3 times higher.

The operation of longer trains with heavier axle loads and the increased and more concentrated traffic on fewer main routes, are contributing factors to the increased cost of track-related accidents.  The anticipated trend is toward even heavier cars with greater axle loads and higher train speeds, thus increasing potential accident severity.  In addition, future demand for more passenger and commuter service operating at higher speeds will further tax the capacity of existing routes while also reducing available track maintenance time.  Track in these shared passenger and freight corridors will be subjected to more demanding requirements—heavier load carrying capacity, greater durability for freight service, and greater geometric precision for faster passenger service.

Objectives       

The primary objective of the FRA’s Track and Structures Research Program is to reduce accidents, deaths, injuries, and property damage related to track and other infrastructure failures.

Another objective is to anticipate and address safety issues concerning emerging technologies before their widespread use and to facilitate their safe implementation in the future.  These objectives are achieved by providing the technical basis for the development of safety standards and best industry practices for maintenance, inspection, and train operations.  The Track and Structures Research Program has been evaluated through a five-step “fault-tree” process, described in Chapter 3 , with the objective of developing an explicit rationale for project selection and program development.

The Track and Structures Research Program is directed along three fronts, described in more detail in the remainder of this section.  First, is the development and implementation of techniques to more effectively and rapidly locate track defects and to better assess track conditions.  Second, is the assessment and shared development of improved track and structure materials and components to withstand higher loads and provide greater durability and safety.  And third, is the examination of techniques for improving the performance of the track structure as a whole, to provide a more viable and stable structure under heavier loads and higher speeds. 

Inspection Technology and Data Analysis   This research area has the two objectives.  One is to improve the efficiency and effectiveness of track, bridge, and roadway inspection.  Another is to develop methods for more effectively applying inspection data to improve diagnostic capabilities and track maintenance planning, and to optimize inspection scheduling.

To achieve these objectives, the research will emphasize the development and adaptation of improved sensor and computing technologies, as well as the integration of advancements in wireless communication and location identification technologies, such as the Global Positioning System (GPS).  Increased efforts will also be made in the development of sensors for measuring vertical track support and the potential use of Ground Penetrating Radar (GPR) as diagnostic tools in identifying track defects due to subsurface conditions.  These are part of the Intelligent Railroad Systems activities described in Chapter 2 .

FRA research has produced several generations of instrumented railcars, the latest of which are the T-6, which measures the gauge holding strength of track, and the T-16, which measures track geometry, wheel/rail forces, and ride quality at track speeds reaching up to 150 miles per hour. To quantify track conditions and to determine operational safety, software aboard these cars compares the measurements to the Federal Track Safety Standards, as well as other established or proposed performance guidelines, and provides accurate mapping and description of all identified defects. 

Data from these cars also supports the development of track degradation and vehicle/track interaction models, which are part of the Track and Structure Design and Performance, and the Track/Train Interaction research areas.  The future integration of inspection techniques with track degradation and vehicle-track interaction models will allow instant update to track maintenance plans, as well as real-time evaluation of operational safety, as inspections are being performed.

Future efforts will monitor the pace of developments in the emerging fields of micro-electro-mechanical systems (MEMS) and nanotechnology, which promise to allow molecular-sized condition sensors to be embedded into track components during manufacturing.  As part of a remote health and condition monitoring system, the wireless micro-sensors may transmit a condition alarm to a location or be read by inspection cars passing over the track.  Nano-sized sensors embedded in rail or other track components could also measure stress levels, a capability that may greatly improve the buckling safety of continuously welded rail.

Materials and Components Reliability

Some accidents and infrastructure deficiencies relate directly to weaknesses or defects in individual components or materials.  This research area focuses on collaboration with industry efforts to improve the design, material composition, and repair of individual components to withstand the increased demands from heavier and more frequent axle loads, and in particular rails, ties, fasteners, and switch components.  Other efforts focus on improving the understanding and modeling of defect formation and propagation, and enhancing the ability to predict defect growth rates for timely action before accidents can occur.

The products from this project group will help produce stronger and more durable components and materials, more effective repair and maintenance techniques, and therefore fewer accidents and derailments due to such failures.  The knowledge gained will also serve as a rational basis for enhanced FRA safety standards and rules for inspections and mandated remedial actions, as in the safety critical areas of internal rail defects and rail welds, and for guiding improved industry practices for maintenance planning and structural repairs.

Track and Structure Design and Performance

Beyond the component level, other accidents and infrastructure deficiencies result from the deteriorated behavior of the track structure as a whole.  In these cases, the problems and needs must be addressed through consideration and understanding of the interaction between track components. 

The products from this project group will help produce a more stable track structure along with models to predict track deterioration under a variety of conditions.  These new techniques will serve as the basis for performance-based track safety standards.

Expected Outcomes

Expected outcomes are:

• Better understanding of fracture development and growth mechanisms in rail steel under passing loads.
• Improved nondestructive (field) test methods for detecting flaws in rail steel.
• Improved methods for determining when track is at risk of sudden lateral buckling or of pulling apart from rail longitudinal forces induced by seasonal temperature changes or by tractive or braking forces.
• Advanced inspection technologies to detect track hazards (e.g., track bed weakness, wide gage, and faulty geometry) well before accidents can occur, as well as safe load capacity and structural integrity of bridges.
• Incorporation of research results into FRA Track Safety Standards and railroad maintenance practices.

Project Descriptions

INSPECTION TECHNOLOGY AND DATA ANALYSIS

Rail Defect Detection

This effort is aimed at producing better and faster methods for detecting internal rail and joint bar defects and developing automated methods for better and more consistent interpretation of rail defect measurement data.  Plans include expansion of a Rail Defect Test Facility (RDTF) at the TTC.  The RDTF is a track containing a wide range (in both type and size) of well-documented internal defects.  Additional samples will be installed to include rails with both internal and surface defects as well as other examples of defects, or defect combinations, which have proven difficult to reliably detect.  The RDTF will be used to accurately measure the performance of existing detection methods, and then, to diagnose detection deficiencies.  From these evaluations, improvements in detection methods and in interpretation of detector measurement data can then be proposed and developed.  Improved defect management and repair practices can also be formulated.  This work will continue throughout the next five-year period. 

Alternative Techniques for the Detection of Broken Rail or Track Hazards

This project will assess the application of new technologies other than those normally used for the detection of broken rail.  Special emphasis will be placed upon the feasibility of a train-mounted device for detection of broken rail or other hazards ahead of a moving train.  Currently, track circuits for signaling also provide for the detection of broken rail.  However, about half of the railroad mileage does not have signal circuits and is otherwise not equipped with a broken rail detection system.  In addition, signal circuits are not fully reliable in detecting broken rails.  Even where signal circuits are present and a rail breaks without the presence of a train, signals will not always show “Stop” if a rail breaks over a tie plate.  Initial efforts will focus on broken rail detection, followed by track hazard detection in general. 

Longitudinal Rail Stress Measurement

The ability to measure internal rail stresses is essential for accurately predicting track buckling potential and for prescribing the most effective remedial action to prevent buckling.  It is also important for controlling rail pull-apart.  This capability has long been desired in the railroad engineering world and the FRA will continue pursuit of this objective.  To date, track-mounted methods have shown some success, but what is needed is a method to make these measurements continuously along the track at moderate-to-high speed.  A prototype for making localized measurements is planned for FY 2003, with field-testing planned for FY 2004.

Track Gage Widening and Strength Measurements

One of the major causes of derailments is widening of the track gage due to weakened ties and/or fasteners.  The resulting inability of track to hold gage under load often causes the wheels of a passing train to drop between the rails.  In response to this frequent mode of derailment, the FRA developed the T-6 inspection car, which is equipped with the Gage Restraint Measurement System (GRMS), to measure track gage and its holding strength continuously along the track. The T-6 GRMS car has demonstrated consistent ability to detect weak track locations due to unsatisfactory tie and/or fastener conditions.  The successful development and deployment of this inspection technology over the past few years culminated in its full use and acceptance by the industry as well as its recent incorporation into FRA’s Track Safety Standards as an alternate performance-based standard.

FRA will continue its GRMS testing program for the mutual benefit of FRA’s R&D and safety programs and the cooperating railroads.  Current plans are in effect for upgrading the aging T-6 to provide for a self-propelled platform and for the modernization of data collection, location identification, and communication systems.  The GRMS program will also continue to support FRA Office of Safety in the evaluation of waiver requests from the railroads, and in the implementation of the recently enacted safety standards.  Data collected from these activities will also provide critical input to the parallel development of the Track Degradation Model and for determining optimum inspection frequencies.

Current gage restraint measuring capabilities, developed through FRA research, include the GRMS vehicle which is suitable for measuring up to 200 miles per day on a production basis, and a simple manual device, the Track Loading Fixture, which is suitable for measuring gage strength at selected spots.  While this type of production testing is well suited for major railroad tracks, it is not as cost effective or practical when testing on short line railroads, through yards and sidings, and on branch lines of major systems.  The feasibility of a more easily deployable and lighter system for gage strength testing that can meet the need for smaller scale testing in a cost-effective manner will be investigated.

Vertical Track Support Measurement

Vertical deflection measurement can enhance the maintenance of safe track structures by locating areas of inadequate or non-uniform vertical support.  Such conditions, which are generally not detectable through visual inspection of track, may be due to improper maintenance of transition points, such as bridge approaches, poor drainage, or poor soil load-bearing capacity under the track structure. 

Currently, few systems are able to measure vertical track deflection under load using wayside, static techniques.  These systems are typically installed at a specific location along the track right-of-way, and some may require that instrumentation be imbedded in the base layer beneath the track.  While generally accurate, the existing systems are costly to install and maintain, and can only provide “spot” measurements of vertical track stiffness, and thus are of limited usefulness in wide-area inspections.  Therefore, the FRA has determined that a more cost-effective vehicle-bound measurement system that can make continuous stiffness measurements under load will provide a much needed enhancement to track safety inspections.

A feasibility study commissioned by FRA has identified two potential approaches for obtaining this vertical track stiffness measurement from a moving vehicle.  One approach will exploit the relative motion between unloaded and loaded wheels using accelerometers, while the other will attempt a direct measurement of rail deformation using laser transducers.  Research currently underway in collaboration with Amtrak will test and evaluate the suitability of both techniques. If further feasibility is concluded, a prototype system will be developed and further tested on the FRA T-16 research car.

Automated Inspection of Roadbed 

Track subsurface layers (ballast, sub-ballast, and subgrade) provide the required support to the track structure.  Poor subsurface conditions result in poor track performance as well as excessive and uneven track degradation.  Uneven degradation results in costly maintenance and adversely affects track safety. 

Since ballast, sub-ballast, and subgrade layers are beneath the track structure, they are difficult to properly inspect with purely visual methods.  Currently, there is no practical method for rapid subsurface evaluation.  However, emerging technologies, such as ground penetrating radar and sonic or vibratory signals, offer promise for developing both improved and automated roadbed inspection capabilities.  In collaboration with experts from industry and academia, these technologies will continue to be investigated with further development of the most promising technologies.

Non-Destructive Evaluation (NDE) of Bridges

As freight car weights increase and bridges age, the need for effective, rapid bridge inspection and strength evaluation methods increases as well.  The FRA will work jointly with the FHWA and the AAR to investigate NDE technologies that may be applicable in automated bridge safety monitoring.  The intent is to pursue techniques that show a high potential for successful adaptation and deployment.  This will be a continuing activity.

Automated Analysis and Interpretation of Inspection Data

A key element in raising inspection speeds and in improving inspection effectiveness is taking better advantage of the large amount of data produced by modern inspection techniques.  Efforts in this important but often neglected area of research will focus on innovative and improved ways for real-time viewing and display of inspection results and the production of relevant and meaningful inspection reports and summaries.  Automated analysis and interpretation will permit diagnosis of many conditions at the time inspections are being made, taking into consideration more variables than can be practically incorporated into the process by slower, manual methods.  A variety of track and structure inspections will be benefit from this research.

Probability-Based Inspection Criteria

Many standards for quality control and safety assurance throughout the industrial world are now based on probability theory, data, and estimates.  In this group of projects, the sciences of probability and engineering reliability will be applied to develop criteria for inspection scheduling and for characterizing track condition during an inspection.  A probability-based inspection schedule would emphasize sections of track with a higher likelihood of having defects.  It would also consider the likelihood of missing defects in areas and under conditions where inspection is more difficult.  With a probability-based approach, the severity of a defect is related to a combination of its likelihood of leading to a failure before the next scheduled and the likely consequences if a failure would occur.  This approach will be developed to cover a wide range of track and track/train interaction inspection.

MATERIALS AND COMPONENTS RELIABILITY

Rail Integrity

Rail integrity research is aimed at extending the life of rail until it must be removed due to either fatigue failure or wear beyond allowable limits.  This research includes the study of rail steel properties; defect formation and growth rates; the effects of residual, thermal, and train-applied stresses; surface wearing characteristics; and maintenance grinding and lubrication practices.

FRA will continue to support the development of rail steels that are more resistant to defect formation.  Studies in this area will focus on factors that control rail service life and performance, including growth of fatigue cracks, influence of metallurgy, and the influence of rolling loads on residual stress formation and its relationship to fatigue defect initiation and growth.  Future work in this area will concentrate on appropriate actions to be taken to: (1) remedy detected defects, (2) improve the metallurgy through processing and post processing of rail steels, (3) assess the safety implications of various rail grinding and lubrication procedures, (4) investigate optimum rail section design to extend rail life while reducing the risk of accidents.  Defect growth studies will continue in FY 2001-2003, with validation of growth prediction models planned for FY 2003-2005.  

While not viewed as a major cause of accidents, worn rail is suspected of being a contributing factor in some cases.  The exact nature of its contribution, though, is not well understood.  The wear pattern on the rail may be as important as the amount of wear on both the top and gage side of the rail head.  Investigation of the effects of worn rail is planned beginning in FY 2002 to provide a better understanding of what problems worn rail may create.

Rail Welding

Despite recent improvements in the process, welds made in the field to join sections of rail or to make repairs still experience high rates of failure.  Studies to date of the effects of heavier cars on track indicate that weld failure rates may increase further without better methods to achieve a higher and more consistent field weld quality.  This project will support the development of improved materials and processes to produce welds that are less susceptible to defect formation.  This will be a continuing activity.

Turnouts and Track Crossings  

Turnouts and track crossings are often categorized as special trackwork, as they include a variety of hardware, fastenings, and general construction that is different from typical track structure.  Turnouts and track crossings are subjected to especially high lateral forces and large vertical impacts, and therefore, higher wear and failure rates.  The beating they receive has been increasing as heavier freight cars enter service in greater numbers.  As axle loads increased, special trackwork components have been deteriorating at an accelerated rate and have become more subject to rapid failure.  For the 5-year period from 1996 through 2000, turnouts and track crossings were responsible for an average of about 200 accidents and 2 injuries each year.  The average annual reported damage was $8.7 million.  This represents about 20 percent of all track-related accidents and 9 percent of all track-caused accident damage.

This project, in collaboration with the railroad industry, focuses on improving the geometric and material design of these components to better withstand the higher forces and impacts of heavy axle loads as well as reduce wear and deterioration rates.  Promising alternatives to conventional designs will be tested on the FAST track at TTC to determine their performance and durability.  Results from these tests will help to develop improved designs that will withstand expected future load levels.  This will be a continuing activity.

Ties and Fastenings

Railroad ties are typically made of wood.  In recent years, a substantial number of concrete ties and a small number of steel ties have been installed on U.S. railroads.  Now, ties made of recycled plastic of a variety of designs, glass fiber reinforced wood, and reconstituted wood dust are being produced, together with a variety of rail fasteners, from spikes to special design clip type fasteners.  In particular, plastic ties have already penetrated the market, with thousands being installed at various transit properties.  FRA will continue to cooperate with the railroad industry in this area to test and monitor the performance of these new components and materials and will participate in industry-sponsored workshops and seminars to facilitate the exchange of information between potential users, manufacturers, and the engineering community, to build a consensus for minimum performance requirements for their implementation and safety evaluation.

Ballast and Subgrade

In addition to the innovative inspection techniques for subsurface evaluations, which were outlined in the previous section, FRA will continue to research the causes for ballast and subgrade degradation and failure, and in particular with respect to fouling and drainage.  Studies regarding ballast particle size and shape (i.e., number of faces, edges, and corners) also appear to offer promising results.

Composite Materials for Railroad Infrastructure

Composite materials have been increasingly recognized as viable construction materials for a wide range of structures with distinct advantages in some special applications.  These advantages include: light weight, high strength, wear resistance, corrosion resistance, dimensional stability, and design flexibility particularly in forming complex shapes.  Ultimately, the potential for their increased use in railroad infrastructure applications is their competitive advantage on a life-cycle-cost basis.  Ongoing studies at West Virginia University and the University of Missouri at Rolla under the FRA university research grants program will focus on investigating load transfer characteristics between the old and new materials as well as the reliability of connections and durability of the new materials.  This effort is planned to run through FY 2002.  Future efforts will include the investigation of the potential use of Smart Tagged Composites in structural elements. In these applications, it is envisioned that the tags can be interrogated or monitored using conventional non-destructive techniques with respect to predefined condition or response to service loading. 

TRACK AND STRUCTURE DESIGN AND PERFORMANCE

Track Performance under Heavy Axle Loads

This project has three focus areas.  The first provides support for operation of the joint FRA/AAR-funded Facility for Accelerated Service Testing (FAST) at TTC.  It includes the operation of the heavy axle load train around the FAST track that enables the performance of subgrade, ballast, ties, fastenings, rail, and track stability to be evaluated in a controlled laboratory-type environment.  The second focus area is the evaluation of heavy axle load effects in actual railroad revenue service.  This will allow a wider range of variables to be evaluated than can be achieved at FAST.  The third focus is on branch lines and short lines, where track and bridge construction is often different from that found on main line railroads.  This effort is being carried out cooperatively with the American Short Line and Regional Railroad Association.  The heavy axle load experiments have significant safety implications and will provide the technical support on which to base improvements in safety regulations.  This will be a continuing activity.

Track Degradation Model

A computer model for predicting the character and rate of track degradation has been long desired in the railroad industry and research community.  Such a model would provide many important benefits, including showing the effect of track defects which occur in combination.  Presently, the track safety standards are, to a great extent, based on individual defects because the ability to clearly define combined effects has not existed.  This effort would focus on combining elements of the complete track degradation model, which have been developed over the years but have not yet been integrated into a comprehensive model that accounts for the proper interaction among them.  Factors leading to track surface deterioration will be properly quantified, both at the component and system levels, as they act in combination. The result of this project will be a complete track degradation model that will be used as a basis for a more rational maintenance planning and a more optimum safety inspection scheduling.  The model will also support the development of performance-based track safety standards.  An initial model is planned for 2003, with further refinements to follow.

Upgrading Track for High-Speed Operation            

FRA’s report of September 1997, High-Speed Ground Transportation for America, indicated that the most practical and economically feasible way of providing high-speed rail service to U.S. corridors is to upgrade existing routes and provide for their joint use with freight trains.  Although generally less expensive than all-new construction, upgrading tracks for joint high-speed passenger train and freight use presents its own complications and challenges.  The main complication is providing a track structure that will practically accommodate two uses with such differing requirements—lightweight passenger trains at high speeds and heavily loaded freight trains at slower speeds. 

This project focuses on two tasks: roadbed rehabilitation, and track structure design.  One issue in a successful upgrading of track is the extent of roadbed rehabilitation required and the cost-effective methods for accomplishing it.  Another is building a track structure on the roadbed that will provide the precision surface and alignment required for high speed service, while at the same time, withstand the heavier loads of freight service without experiencing rapid deterioration or requiring constant maintenance.  Results from this project will lead to the development of: