Safety Criteria for Evaluation of the Railway Vehicle Derailment
Hiroaki ISHIDA, Kazuhiko TEZUKA, Kenji UEKI, Katoshi FUKAZAWA, Masaki MATSUO
The maximum value of derailment quotient Q/P has been used for the evaluation of
vehicle running safety. The derailment quotients sometimes exceed the standard value
momentarily, when the wheel load is reduced by the wheelset oscillating with high
frequency, or when the lateral force increases as the wheel flange hits the rail.
The safety has to be secured by means of the established evaluation method without
fail, but it is also important in practical use that there are few misjudgements
(or overstatements), when it is declared as "dangerous" despite no hazard of derailment
because the flange does not climb the rail. This paper deals with a search on the best
parameter and criteria for the evaluation. According to the results of computer
simulations and experiments using a 1/5 scale wheelset, both the derailment quotient
Q/P and the duration of Q/P exceeding the limit value, or the sliding mean value of
Q/P using the time window is suitable as the criteria in order to evaluate the safety
against the derailment accurately.