Experimental Comparison of Manual and Voice Controls for the Operation of in-Vehicle Systems

Abstract

Many previous research studies have found that the operation of in-vehicle systems while on-the-move using traditional manual controls (buttons, switches etc.) can adversely affect driving performance. It has been proposed that voice operation can reduce these effects by allowing the eyes to remain on the road, and the hands to remain on the steering wheel. A counter-argument to the incorporation of voice control is that, by mounting manual controls on or near the steering wheel, similar benefits can be experienced. To examine these arguments, a study was designed to compare different types of control for operating an in-car entertainment (ICE) system, incorporating radio, tape and CD functions. Thirty two participants carried out tasks using either (i) standard manual ICE controls, (ii) manual steering wheel button controls, (iii) voice controls with spoken and visual feedback, or (iv) voice controls with no feedback. The ICE was operated alone, or while carrying out a simultaneous PC-based driving task using steering wheel and pedals. Driving performance was found to be significantly better while using voice controls than the manual controls. Transaction times while driving were shortest for the standard controls, intermediate for the voice conditions, and longest for the steering wheel controls. Subjectively, the voice controls with feedback were rated easiest, most likeable, and most efficient to use while driving.