It has been a well-established fact that excessive wheel/rail loads cause accelerated wheel/rail wear, truck component deterioration, track damage, and increased potential for derailment. The economic and safety impact of the increased wheel rail loads can only be ascertained by a total characterization of the wheel/rail loads. In this paper, a comprehensive set of experimental results obtained from on-track testing of conventional North American freight cars using both wayside and on-board measurement systems are presented. The particular emphasis is given to the wheel/rail loads resulting from suspension dynamics. The dynamic wheel/rail environment addressed in this paper is limited to dynamic performance regimes such as rock-and-roll and pitch-and-bounce, hunting, and curving. The strong dependence of the dynamic response of a railway vehicle on a truck suspension system has been illustrated by comparison of controlled test results for vehicles of different types.

Growing understanding of the interactions between vehicle and track continues to provide benefits in both performance and safety. Recent advancements in freight car modeling and testing procedures have enhanced the understanding of wheel/rail dynamics and continue to provide guidance in dynamic system testing (1, 2). Development of experimental techniques to accurately measure the wheel/rail loads using instrumented wheel sets has made it possible to determine the total load environment seen under railway cars over long stretches of track (3). Many large-scale on-track tests have been conducted by railway researchers to characterize the dynamic performance of railway vehicles using state-of-the-art computer-based data acquisition systems (4-6). The Association of American Railroads (AAR) has been an active participant in conducting extensive analytical and experimental vehicle dynamics research through the years. In this paper we have attempted to bring together the results of some of the experimental research conducted by the AAR, regarding dynamic load environment for conventional freight cars.