“…Subjective ratings are not as sensitive to small changes in vibration; for example, reductions in vibration magnitude of less than 10% are generally undetectable by subjective ratings ( Morioka and Griffin, 2000 ). Meanwhile, in the acceleration-based method, the international standards ISO 2631-1 and BS-6841 proposed a ride index to quantify discomfort by applying a frequency weighting and axis multiplication factors to accelerations measured at different locations on the body ( Griffin and Erdreich, 1991 ; Griffin, 2007 ; Badiru and Cwycyshyn, 2013 ; Taluja et al, 2017 ). Several studies have used the ride index to evaluate discomfort in different modes of transport, such as a car ( Cantisani and Loprencipe, 2010 ; Song et al, 2023 ), a train ( Zoccali et al, 2018 ), a helicopter ( Delcor et al, 2022 ), and a cruise flight ( Huang and Li, 2023 ).…”