Assessing driving capability: a method for individual testing: the significance of paraparesis inferior studied in a...

The part played in traffic safety by driver illness or disability is uncertain or unknown. So also are the specific identity and degree of the disorders which necessitate the use of driving aids or which completely incapacitate a person from driving. Despite the gravity of the problems, the question of fitness to hold a driving licence is decided throughout the world mainly on the basis of subjective assessment. Controlled experiments exploring the significance of disorders have only been carried out on a restricted scale. In this paper a description is given of a mock car, which is used both for research and individual assessment. It enables the measurement of strength application, steering wheel turn speed, simple reaction times when operating pedals and steering wheel, erroneous reactions, and choice reaction times. Experiments involving 109 able-bodied and healthy persons showed, as expected, that the muscular strength of men was greater than of women, and that men were significantly quicker at carrying out functions which primarily depend upon speed of movement and of strength. Apart from this, however, there were no significant sex-related differences. Almost all variables showed age dependence, this being most pronounced in the case of men. Thirty-two percent of the test candidates committed errors like braking instead of turning the wheel or turning to the wrong side. Neither the incidence nor the seriousness of errors bore any relation to sex or age. Fifty-two persons suffering from paraparesis inferior were compared with the 109 able-bodied subjects. The degree of paresis co-varied with reaction times, but the degree of spasticity only to a minor extent. The results indicate that at a speed of 80 km/h, 'slight paresis' increases reaction distance by around 2-3 m (15%), and 'moderate paresis' by the region of 50 m.