Usability Evaluation of Handlebar Geometry for Steering Operability in a Semi-Recumbent Quadricycle

Abstract

Last-mile mobility is increasingly important in tourist areas, where safe and convenient short-distance transportation is required. The authors are developing a license-free personal mobility vehicle: an electric-assist quadricycle with a semi-recumbent riding posture that allows riders to enjoy the surrounding scenery. This quadricycle employs front-wheel steering and rear-wheel drive, resulting in structural and steering characteristics distinct from conventional bicycles. However, handlebar options are often limited, as components are typically repurposed from standard bicycles. Therefore, it is crucial to evaluate whether such handlebars are ergonomically suitable for quadricycles and how they influence steering operability. This study investigates the influence of handlebar geometry on steering operability in a semi-recumbent quadricycle, focusing on subjective ratings of braking and steering. Experiments were conducted using a prototype vehicle, SQC-03A. Three common bicycle handlebar types—straight, bullhorn, and butterfly—were examined, with two gripping configurations for the butterfly handlebar, resulting in four experimental conditions.Participants included 10 male university students who performed braking and steering operations on a stationary vehicle. Usability was assessed using a five-point subjective rating scale. Results indicate that the straight handlebar achieved the highest usability ratings for both braking and steering, whereas the bullhorn handlebar received lower ratings. This may indicate an ergonomic mismatch; the bullhorn geometry encourages a forward-leaning posture that is incompatible with the semi-recumbent position supported by a backrest. These findings suggest that straight handlebars provide superior usability for semi-recumbent quadricycles. However, long-term fatigue and variations in grip strength should also be considered.

Keywords: Personal mobility vehicle (PMV), Ergonomic evaluation, Steering operability, Handlebar geometry

DOI: 10.54941/ahfe1008152