Lateral instability of rail vehicles, more colloquially known as “hunting” is a dynamic instability mode of high importance. In extreme cases hunting can lead to derailments, but more frequently it is the cause of a number of less catastrophic yet costly damages to track, truck, and lading.

It is known in the railroad industry that wheel conicity inherently affects the stability of the rail car on the track. Additional factors include reduced warp restraint of the truck system, low truck/car body rotational resistance due to degraded side bearings, and hollow worn wheels. Nonetheless, reconditioning of these components does not always lead to the desired result of reduced lateral accelerations. Furthermore, with trains often consisting of up to 200 cars, worn truck systems may go undetected for long periods of time until either a Truck Hunting Detector (THD) or visual inspection reveals the issue.

Accurate detection of hunting and estimation of hunting severity remain challenging tasks. The network of truck hunting detectors is sparse, provides limited insight, and is expensive to expand and maintain. Furthermore, the nature of the detection method does not provide the user with information about the cause of the failure. This increases the probability of reoccurrence of lateral instability in reconditioned truck systems.

In this paper, the root causes, dynamic behavior, and existing measurement techniques are evaluated. Additionally, a novel method to detect dynamic instability is presented. This method has been developed to provide a new way to examine dynamic instability in a more direct and detailed manner. A preliminary study to evaluate the proposed method has been completed and the results are presented in this paper. To evaluate the benefit of the proposed method, the test data is measured against AAR limits.

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