This paper presents the findings of a survey carried out on 7254 British drivers. High and low contrast LogMAR visual acuity were measured using a Titmus vision screener. A questionnaire established (1) visually motivated voluntary driving restriction and (2) at-fault accident involvement during the previous five years for which vision was considered to be an important factor. Drivers were asked to indicate the incidence of driving restriction or accident involvement under one good visibility condition (good daylight) and three poor visibility conditions (poor daylight, good night-time, poor night-time). Relationships between vision (high contrast visual acuity, low contrast visual acuity and contrast susceptibility), age, driving restriction and accident involvement were statistically analysed using Kendall's rank correlation. Driving restriction decreased accident involvement. Controlling for the effects of age, a statistically significant increase in driving restriction was found with reduced high contrast visual acuity. Neither reduced low contrast visual acuity nor contrast susceptibility caused any additional increase in driving restriction. As might be expected, more driving restriction was reported for poor visibility conditions. In good visibility, reduced high contrast visual acuity, but not advancing age, gave rise to a statistically significant increase in driving restriction. In poor visibility, both reduced high contrast visual acuity and advancing age bought about a statistically significant increase in driving restriction. In the latter case, reduced high contrast visual acuity still exhibited the strongest effect. In conclusion, voluntary driving restriction appears to be influenced more by high contrast visual acuity than low contrast visual acuity. Further, reduced visual acuity appears to be more important than age as a factor influencing driving restriction and ultimately accident involvement. (A)
Abstract