This is a report of some exploratory studies aimed at evaluating the conspicuities (attention-attracting powers) of a group of commercial warning lights meant for use on emergency vehicles. The main experiment used a novel technique of conspicuity matching. Each observer, in turn, fixated straight ahead and viewed two flashing lights peripherally, one located 20' to the right. One of the two lights was always a reference light whose intensity could be adjusted by the observer until the two lights appeared equally conspicuous. All the lights were thereby ranked on a single scale of conspicuity, based on the adjustable-light intensities. There was a good correlation (r=0.90) between these ranks and the measured effective intensities of the lights. Another, very brief, pilot experiment ranked some of the lights according to the number of degrees into the left side of the visual field that the flashes could still be seen. This disappearance-angle rank also correlated well (r=0.86) with conspicuity rank. Problems encountered and suggestions for future improvements are discussed.
Abstract