Performance of visually impaired heavy-vehicle operators

Abstract

The 2-year accident and conviction rates, subsequent to licensure vision testing, of visually impaired heavy-vehicle operators (who are restricted to driving heavy vehicles only within California) were compared with those of visually nonimpaired heavy-vehicle drivers. Nonimpaired drivers met current federal acuity standards of 20/40 or better in each eye, while impaired drivers had substandard static acuity in one eye. The impairment status of the latter group was categorized as being either moderate (substandard eye better than or equal to 20/200) or severe (substandard eye worse than 20/200). California and nationwide mileage estimates, obtained through a mailed questionnaire of unpaired drivers and a sample of unimpaired study drivers, did not differ significantly between impairment groups, but the response rate was very low. This and other sources of potential bias are discussed. After adjustment for age, visually impaired groups combined had significantly and substantially more traffic accidents and convictions than did nonimpaired drivers. In consideration of possible biasing factors, it was concluded that the results provide limited support for the federal standard, with greater support for its application in the case of severely impaired heavy-vehicle operators.