Retroflective sheeting materials on highway signs

In a road research project, older drivers were asked to read street names as soon as they were able as they were approaching an intersection. The signs were always on the far sides of the intersection but could be either on the right or left side. Intersections of three levels of complexity were used. A repeated measures design was used. All main effects and all but one of the interactions were significant. The legibility distances obtained from 864 trials using 18 subjects showed that Diamond Grade and VIP Diamond Grade sheeting were equivalent but that both were significantly superior to High Intensity Grade sheeting which was in turn significantly superior to Engineering Grade. The differences among sheeting grades were more apparent at the more complex intersections. The viewing conditions on some of the streets resulted in reduced visibility and conspicuity causing markedly reduced legibility distances. There were no performance differences based on gender. The implications for driving safety were discussed in the context of visual information processing workload, divided attention and multitasking.