Car Control knob usability: a posture based comfort assessment

Today, people spend much more time in the car, especially the ones that drive for job (taxi driver, couriers, truck drivers, etc.); for this reason, several studies have been performed on car interiors in order to improve the driver and passenger comfort experience. The aim of this study was the evaluation of perceived comfort while using the infotainment board system inside a C-segment car MY2012. The Car manufacturer claims to guarantee connectivity to its users, but also to ensure the same "web comfort" of a PC or smartphone even when it is on the go. To prove that, a sample of twenty-three students performed three different tasks in a Mercedes class A180 CDI EXECUTIVE. Postural angles of students had been acquired non-invasively by cameras and processed by KINOVEA® software. A further virtual-postural analysis had been realized with a DHM (Digital Human Modeling) software. Subjective postural comfort has been evaluated through questionnaires by which participants were asked to rate on a 10-point Comfort scale the expected comfort before beginning the test and on a 9-point Likert scale the perceived comfort after using the knob. Objective postural comfort had been gathered through CaMAN® software. Finally, a large multivariate analysis had been done to evaluate the correlations among the data (anthropometric data, subjective and objective postural comfort). Results showed which could be the most comfortable position of the knob and which body-part mostly contributed to global perceived comfort.