Insight into the lateral ride discomfort thresholds of young-adult bus passengers at multiple postures: Case of Singapore

Ride comfort is an important serviceability attribute for bus passengers, of which bus operating under the influence of road layout in urban roads is a prominent contributory factor. Passenger posture is another influencing factor that has not yet been investigated comprehensively. In this case study, ride comfort from road-induced lateral acceleration and lateral jerk was assessed by correlating subjective evaluation with bus operation performance parameters as well as road layout in Singapore. In the first bus run, a sample of 26 participants classified in three groups: sitting, leaning and standing postures, rode on the same bus along a 45-min route. Ride comfort was worst-off for standing passengers and least uncomfortable for sitting passengers. A strong statistical correlation was found between participants’ subjective ratings with lateral acceleration and duration of turning movement. A second bus run was followed with a sample of 11 participants to collect additional passengers’ ratings. Lateral ride discomfort thresholds were thus established for bus negotiating roundabouts, intersections and along links. The three levels of ride discomfort are Uncomfortable, Very Uncomfortable and Extremely Uncomfortable with average lateral accelerations of a_y = 1.5, 1.75 and 2.0 m/s², respectively. The lateral ride discomfort thresholds would be useful for several value-add applications which include better vehicle design including its interiors, and better vehicle handling about the road layout. With the advent of autonomous public transport (APT), the ride discomfort thresholds must also be considered as valuable input for APT vehicle operation.