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 sub-grade characteristics together with the tracking behavior of the trucks that support the railroad car.  Research efforts are now being planned 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.  The main purpose of this study will be to objectively determine the reduction of track quality over time under service, to develop recommended inspection and maintenance intervals, and to predict the onset of unsafe track conditions if adequate maintenance is not applied.

Future activities will aim to 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 the FRA’s track geometry standards and guides the FRA’s inspection policy and frequency.

Wheel/Rail Interaction & 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 will continue until FY 2002.  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. Another cooperative agreement between the FRA and the National Research Council of Canada will be focusing on the wheel/rail friction management and profile optimization for commuter and passenger rail services.   This work will continue with FY 2004.  A second cooperative effort between the FRA and the AAR (this is one of the AAR’s Strategic Research Initiatives) aims to improve the understanding of various derailment mechanisms, such as wheel climb, wheel drop, or rail roll-over derailments, that can be caused by defects in wheel and/or the rail surface will continue till FY 2002.  An increased awareness of the causes of such derailments will lead to better track inspection and maintenance practices and ultimately reduce the risk of such derailments. 

Forces in Special Trackwork

Research in this area aims to examine methods and techniques for reducing wheel/rail forces that are generated when traversing special trackwork. Emphasis will be given to 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.

2.  VEHICLE-TRACK PERFORMANCE

Vehicle/Track Interaction Safety Standards

Under this research program, the FRA has provided two instrumented wheel sets to Amtrak to measure wheel-rail forces under the Track Quality Measuring System -- Car 10002 -- for assessment of maintenance requirements for high-speed operations on the Northeast Corridor.  The planned activities within this project will provide system checkout and data analysis to characterize the wheel-rail interface. This effort involves staff from the wheel set supplier, Amtrak, and the Volpe Center. The successful completion of this task is important to the proper assessment of the safety of the proposed high-speed operation and its impact on the track structure.  Both ride quality safety limits and wheel/rail force safety limits will be assessed.  This research is ongoing.

In addition to the ongoing wheel/rail force measurements, The FRA has recently issued a comprehensive set of new vehicle/track interaction safety standards that are performance-based and that can apply to all classes of track including the three additional classes designated to apply to high-speed track for service at speeds of 125 miles per hour, 150 miles per hour, and beyond.  FRA R&D will be a continuing partner in this effort with the Office of Safety.  This research effort in safety support is expected to be required to continue for up to five years as the new safety standards are implemented in the light of near-term upgrades to higher speed services on the Northeast Corridor and elsewhere in the country.

Modeling and Simulation of Vehicle/Track Interaction
In support of many of 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: