On March 13, 2013, the Federal Railroad Administration (FRA) published a final rule titled “Vehicle/Track Interaction Safety Standards; High-Speed and High Cant Deficiency Operations” which amended the Track Safety Standards (49 CFR Part213) and the Passenger Equipment Safety Standards (49 CFR Part 238) in order to promote VTI safety under a variety of conditions at speeds up to 220 mph . Among its main accomplishments, the final rule facilitates the expansion of higher speed passenger rail by revising the standards governing permissible operating speed in curves, allowing for higher cant deficiencies in all FRA Track Classes. To ensure safety is not diminished, the FRA Track Safety Standards require railroads to maintain their tracks to stricter track geometry standards whenever they operate at these higher curving speeds and cant deficiencies. These revisions were based on studies that examined the dynamic curving performance of various representative rail vehicles.
This research investigates the steady-state curving performance of truck designs while traversing curves at various curving speeds and cant deficiencies. During steady-state curve negotiation, the axles of trucks generally offset laterally from the track centerline and develop angles of attack increasing the wheel-rail contact forces. Large lateral forces can develop, particularly in flange contact, resulting in increased wheel and rail wear, track panel shift, and the risk of derailment. Depending on the truck design, such forces become larger at higher cant deficiency. An understanding of the steady-state response of a rail vehicle in a curve is essential as it represents a significant part of the total dynamic response.
The curving performance of an idealized rigid truck is analyzed using nonlinear analytical methods for a wide range of operating speeds and unbalance conditions. Emphasis is placed on higher speed curving and the results are used to interpret trends observed during recent field testing with Amtrak’s Acela High-Speed Trainset on the Northeast Corridor.