The effect of colored borders and age on the conspicuity of warning signs in a complex visual environment

Abstract

This laboratory study examined the effect of colored borders and age on the conspicuity of roadside warning signs embedded in cluttered urban environments. Prior research has suggested that a uniform border surrounding a sign will increase its conspicuity. In this study a 10 inch green or white border was placed around a standard 30 inch warning sign. The conspicuity of these signs were compared with a standard size and an enlarged warning sign. A standard sign with red 15 inch square metal flags mounted perpendicular to the top edges was also compared. Twenty young drivers (21-27 years, mean 23.5 years) and twenty older drivers (55-79 years, mean 64.9 years) participated in the study. Subjects viewed a series of 200 slides of complex urban street scenes. One hundred slides contained warning signs embedded at an apparent distance of 250 feet. the other 100 slides contained no warning signs and were used to control guessing. The slide stimuli were displayed with a tachistoscope for 500 ms on a rear projection screen. The subjects task was to identify certain target objects, including warning signs, in each slide. The ratio of hits to possible hits was used to measure relative conspicuity. The 500 ms display time was intended to allow a single fixation, but prevent a search of the scene. The short exposure time was intended to allow hit rates to be a measure of attentional conspicuity. Results were consistent with the hypothesis that a ,uniform border would increase conspicuity. Across all subjects, both border treatments were significantly more conspicuous than a standard sign with no border and an enlarged sign. Red flags were not as effective as borders at increasing a warning signs conspicuity. Age effects were found. Young drivers saw an average of 90.45% of all signs in the study. older drivers saw only 70.01% of the warning signs displayed. Border treatments were beneficial for all subjects, but were especially helpful for older subjects.