The Mann-Whitney U test was applied to each observer's hit rate for each target sign category to compare conspicuity between the deuteranopic and normal color vision groups.
Attention conspicuity was significantly less for deuteranopic observers than for color-normal observers, for both detection and recognition criteria, for all classes of road traffic control devices except the yellow warning signs and blue parking signs.
For both criteria for a hit, search conspicuity was also significantly less for the deuteranopic observers for traffic signal lights, stop signs, red-orange warning signs, and give-way signs but not for the yellow warning signs, green direction signs, blue parking signs, and speed restriction signs.
Attention conspicuity for the deuteranopic observers is 10% to 30% of that for the color-normal observers for some classes of road sign.
The differences in conspicuity for color-normal and deuteranopic observers were of a lesser magnitude for the search conspicuity condition than for the attention conspicuity condition.