Analysis of derailment criteria

Rail transportation systems include high-speed rail, rapid mass transit systems, rail freight, and light-rail transit systems are generally wheel-on-rail systems. Thus, the evaluation of the risk of a derailment is a critically important issue; consequently, researchers have endeavored to identify and evaluate an effective derailment criterion. Nadal's quotient has been widely adopted in the assessment of the risk of a derailment. Although recent studies have sometimes criticized that criterion, it still serves as the basis of new criteria and regulations. This article seeks to investigate the problems associated with various derailment criteria, to point out their features and deficiencies, and then to theoretically illustrate their differences. It has been found that the Weinstock criterion does not correctly consider the tread contact wheel, with the revised Weinstock criteria being proposed to correct that problem. Furthermore, a new criterion has been developed that solely considers the horizontal component of the tangential force at the contact point. The new criterion was compared with the wheel load reduction criterion and other criteria to justify the derailment assessments.