Visualizing distances as a function of speed: Design and evaluation of a distance-speedometer

Abstract

This paper contributes to the research on transportation and human factors by designing and evaluating an ecological human-machine interface for speed and distance control. In the future, traffic management will determine optima for speed and safety distances. Wirelessly broadcasted, the question remains how to present this information to drivers in a way that is easily understood and intuitively followed. To this end, a human-machine interface, called distance-speedometer, was first developed according to the principles of ecological interface design and then evaluated in a driving simulator study with forty-nine participants. It presents augmented distances derived from speed in a head-up display. Using a within-subject design, the distance-speedometer and standard speedometer were compared against each other in two scenarios (car-following & sign-following). Each scenario triggered several speed changes. When reacting to speed signs, driving performance did not differ between the two interfaces. However, with the distance-speedometer, visual workload was reduced as more secondary tasks could be completed. When reacting to speed changes of a car ahead, the engagement in the secondary task did not differ significantly between the two interfaces. However, the variance of speed deviations was significantly lower with the distance-speedometer. Results can be explained by the ability to process the distance-speedometer in a skill-based manner, whereas the normal speedometer demands rule-based behaviour to control the speed. With regard to traffic management, the distance-speedometer might be used to unconsciously influence the driver’s choice of speed in order to increase traffic safety and efficiency.