ABSTRACT
It has been said that most of the information drivers use for driving arrives through the visual modality (e.g., Hole, 2007). It is, therefore, intuitively appealing that standards for driver licensing should include an element of eyesight testing – which, in most regimes worldwide, means a test of static visual acuity (Owsley and McGwin, 2010). EU directive 2006/126/EC states that drivers of private cars and motorcycles should have a minimum binocular visual acuity of 6/12 (decimal 0.5) – that is, the ability to resolve detail at 6 m that a person with standard vision could read at 12 m.
In the UK, candidates for a driving test are required to read a standard number plate (with letters 79.4 mm high) at a distance of 20 m (or 20.5 m for the old style number plates). Although test distances have varied with style of plate, this requirement has been in place since 1935 (Taylor, 2010), and remains as the UK’s interpretation of the EU standard. The number plate test is not without criticism, though. Principally, it is not clear that the test as specified actually meets the EU requirements for visual acuity – geometrically, it is equivalent to a Snellen acuity of around 6/15 (Charman, 1997; Currie et al., 2000). Elsewhere, research has suggested that some drivers might pass the number plate test even though their visual acuity is at or below the EU standard, while others could have better vision and yet still fail the test (e.g., Currie et al., 2000). Indeed, Currie et al. (2000) suggest that visual acuity is a “poor predictor of an individual’s ability to meet the required visual standard for driving.” (p. 990).
