Driving blind: the effects of vision on driving safety and performance

Abstract

Eyesight requirements for driver licensing in the UK need to be reviewed, suggests new research from Brunel University, sponsored by RSA. The number plate test, which only measures static visual acuity, does not correspond well to minimum requirements in EU legislation. More to the point, acuity itself is not necessarily a factor in driving performance. Other aspects of visual ability, such as field-of-view, should be taken into account, says the report.The study of 19 drivers in a driving simulator found that on the whole, steering andspeed control did not get worse when drivers were wearing specially constructed glasses to blur their vision. But drivers did stray off the road more often, and missed more road signs, even at the legal minimum levels of visual acuity. Drivers also found it more demanding when wearing the blurring glasses. Surprisingly, only just over two-thirds of the participants passed the number plate test at the legal minimum standard.These findings suggest on the one hand that the current requirements are not stringent enough, with some elements of driving risk increasing even though these drivers would meet the standard. But on the other hand, the report argues that other tests of eyesight might be more appropriate for driver licensing. The study adds to a considerable body of existing knowledge calling for more evidence-based visual screening tests for driver licensing.The reason for the confusion is that acuity is only one aspect of visual ability. In particular, field-of-view stands out as being especially related to driving performance. So the question may be asked as to why driver licensing regimes persist with tests of acuity to screen their drivers. In fact, moves are afoot to include tests of visual field as well as acuity in the driving test, and the current study supports such moves. Ultimately, though, the number plate test is popular because it is easy to administer – any alternative needs to be equally practical and reliable in screening the right drivers, while not disqualifying those who are capable.Meanwhile, the report also recommends that a review of other standards for road sign design should be considered. If drivers are meeting the legal requirements for visual acuity, but still cannot read road signs, it suggests that the legibility of these signs is inadequate. Other researchers have suggested that road signs are designed for higher levels of visual acuity than the legislative standard for driving. The current report calls for these standards to be harmonised, so that drivers passing the visual screening test can also read road signs.

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ORCID for Mark Young: orcid.org/0009-0001-2594-453X

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