Program Descriptions
DERAILMENT MECHANISMS & PREVENTION
Influence of Track Geometry
Heavy freight trains can cause degradation of track geometry in several dimensional parameters. This degradation can be a function not only of axle loading and speed, but also of subgrade characteristics together with the tracking behavior of the trucks that support the railroad car. Research efforts are now underway to address this problem and to assess the influence of the various elements—track, load, vehicle—to separate their individual contributions, and to assess where improvement in component—track or vehicle—performance will decrease the rate of track degradation under service loads. This study will objectively determine the reduction of track quality over time under service, to aid in the development of recommended inspection and maintenance intervals, and to predict the onset of unsafe track conditions if adequate maintenance is not applied.
Future activities will broaden the base of knowledge regarding the limiting conditions of track geometry parameters that will allow safe passage of trains or may contribute to the risk of derailment. Issues such as vehicle response to multiple repeated or combined track defects will be rationally examined through analysis and testing. The objective is to develop guidelines for track geometry limits based on vehicle performance. Progress in this research program provides support for the continual effort to improve FRA’s track geometry standards and to guide FRA’s inspection policy and frequency.
Other activities will focus on developing rational methods for identifying differing track qualities within the same track class. Current FRA standards identify various classes of track, and subsequently allowable speeds, based on established and fixed limits on track geometry anomalies. For example, tracks may be grouped in the same class regardless of the number of near defects per mile associated with each. Future activities will attempt to further qualify such differences in track quality based on the frequency of anomalies or near anomalies, the prevalence of certain combination of anomalies, the rate of degradation, and the severity of carbody/truck vibrations and wheel/rail forces that may result from the interaction of designated railroad cars with such tracks.
Wheel/Rail Interaction and Lubrication
This is a comprehensive effort that addresses critical behavior of the wheel-rail interface as it controls the safe behavior of the wheel flange on both curved and tangent track. Wheel/rail contact safety is addressed from a systems viewpoint; and specific areas of investigation will include the effects of rail lubrication and railhead grinding upon safe performance of this interface, and in particular their effects on hunting and curving behaviors. This work is planned to continue until FY 2005. Other activities include a cooperative research program between the FRA and APTA to develop wheel and rail profile standards for commuter and passenger rail operations, and a cooperative research program between the FRA and AAR to assess the impact on hollow tread worn wheels on derailment safety. The latter, in coordination with one of AAR’s Strategic Research Initiatives, will provide for an increased awareness of the causes of wheel profile related derailments and ultimately the identification of ways to reduce their risk and occurrence. Another cooperative agreement between the FRA and the National Research Council of Canada will focus on wheel/rail friction management and profile optimization for commuter and passenger rail services.
This work is planned to continue until FY 2005.
Forces in Special Trackwork
Research in this area is intended to examine methods and techniques for reducing wheel/rail forces that are generated when traversing special trackwork. Emphasis is planned on field retrofits and maintenance practices which can reduce the generally high interaction forces that typically result in poor ride quality and high maintenance costs, and in some cases, accidents and derailments. This research is ongoing.
VEHICLE-TRACK PERFORMANCE
Vehicle/Track Interaction Safety Criteria
The FRA has recently issued new vehicle/track interaction safety criteria for the high-speed track classes 6 to 9, which allow operational speeds ranging from 80 to 200 miles per hour. The criteria have been already successfully applied in the qualification of a number of new types of passenger equipment, such as Amtrak’s Acela
Express
trainsets and Kawasaki by-level commuter coaches, for higher speed operations in the Northeast Corridor. This success, however, still pointed to a number of areas that require further research. Examples include the determination of whether additional safety limits are needed to control short wavelength track warp, and the possibility of tighter limits on the allowable net lateral axle load ratio under heavier axle loads to better control track panel shift. FRA R&D will continue its support to the Office of Safety in these safety critical areas to develop an objective assessment of the new standards and to provide rational basis for future refinements and/or revisions. This research effort in safety support is expected to continue throughout the next five years as the new safety criteria are implemented in light of near-term upgrades to higher speed services on the Northeast Corridor and elsewhere in the country.
In a new project that will start in FY 2002, FRA will begin to analyze and establish the requirements for passenger ride safety and quality under high-speed train operations. High-speed rail travel induces vertical as well as horizontal vibrations into the passenger carrying vehicles. These vibrations, which can excite a wide frequency range, are transmitted at the floor level to the traveling passengers. The impact of short duration transient vibrations on occupant safety is little understood. Analysis, and possibly limited laboratory testing, may be required to determine the limits of vertical and horizontal vibrations that may impact passenger’s safety. FRA’s track safety standards for high-speed rail operations intend to limit the dynamic motion of passenger carrying vehicles and additional research is needed to better define the safe and acceptable limits for such motion.
In a complimentary activity, the FRA R&D in collaboration with the Office of Safety, Amtrak, the freight railroads, and various State DOT’s and commuter authorities, will continue the deployment of its latest track inspection research car, the T-16, on designated high-speed rail corridors and other rail passenger routes around the country. These tests will provide FRA with simultaneous measurements of track geometry, wheel/rail forces, and ride quality for safety assessment of current and proposed rail operations. Data from these tests will also provide input for a variety of modeling and analytical activities as described in the above sections.
Vehicle/Track Interaction under Heavy Axle Loads
This research area focuses on the influence of axle load increases on derailment tendencies and other aspects of vehicle/track interaction that are not addressed by consideration of structural strength alone. Recent research by the industry provided the preliminary conclusion that heavier axle loads do not necessarily produce higher lateral to vertical load ratios, parameters which are central to many derailment scenarios including wheel climb. However, recent FRA-funded studies indicated that heavier axle loads could increase the risk of gage widening derailments. Other findings point to the increase in wheel/rail contact stresses and dynamic forces due to the accelerated surface degradation. Continued research in this area will provide FRA with an enhanced understanding of the significance of heavier axle loads to these critical system performance issues and their full impact on derailment and safety. This ongoing research is planned to continue until FY 2003.
Modeling and Simulation of Vehicle/Track Interaction
In support of many of the activities in this area, the development of a comprehensive vehicle-track model and a wheel/rail interaction model
will be necessary for the success of several research and regulatory efforts undertaken by the FRA as a whole. Such an integrated system model can provide, for example, much needed support to:
