Specificity and timing of advisory warnings based on cooperative perception

Abstract

Future perception and communication technologies provide the possibility of assisting drivers by so-called advisory warnings in potentially dangerous driving situations. The effectiveness of such advisory warnings will possibly depend on (1) timing (i.e., time left for avoiding the collision, when the driver is warned) and (2) the specificity of the warnings (i.e., warning content, for example information about the direction from which a hazard is imminent). Using a fixed-based driving simulator, n=21 participants encountered three different conflict situations: a longitudinal (pedestrian entering the road between parked cars), a crossing-path (crossing cyclist at an intersection) and a turning vehicle scenario (vehicle turning at an intersection and taking the driver´s right of way). Advisory warnings about upcoming conflicts were provided via Head-Up Display and accompanied by an unobtrusive acoustic signal. Warning timing (latest possible warning timing t0 vs. two seconds before t0+2s) and warning specificity (depiction of type and/or heading of road user vs. no depiction) were varied. Effects on driving behavior and situation criticality were strongly dependent on warning timing, with early warnings (t0+2s) being more effective than late warnings (t0). In comparison to warning timing, the effects of warning specificity were of minor importance to driving behavior, but had a great impact on ratings of usefulness.