Coupler jackknifing and derailments of locomotives on tangent track

A number of derailments occurred in recent years due to coupler jackknifing, some of them were reported on tangent tracks where conventionally thought to be the safer sections. This article studied coupler jackknifing behaviour and its implications for locomotive safety on tangent tracks from the experience of China heavy haul. Three types of coupler systems were modelled and simulated regarding coupler jackknifing behaviour. Two typical locomotive derailments occurred on tangent tracks were analysed. From the derailment experience, coupler angle self-lock behaviour was introduced and simulated. An approach to determine coupler angles in the jackknifed position was derived and validated with a self-coded program and SIMPACK. Methods to prevent coupler jackknifing were also evaluated with regard to locomotive stability.