A Bi-Parameter Distance Criterion for Flange Climb Derailment

Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), has developed a bi-parameter flange climb distance criterion for vehicles with an AAR-1B wheel/AREMA 136-pound rail profile combination. This criterion is based on tests and simulation results using TTCI’s Track Loading Vehicle (TLV) and a NUCARS™ simulation model. The bi-linear characteristics between the transformed climb distance and the two parameters, angle of attack (AOA) and lateral-to-vertical (L/V) force ratio, was obtained through a nonlinear transformation. The accuracy of the fitting formula is further improved by using the gradual linearization methodology. The bi-parameter distance criterion, based on the simulation results, has been validated by TLV test data. This paper also presents the application to two AAR Chapter XI performance acceptance tests and limitations of the bi-parameter criterion.