Biological and behavioral factors affecting driving safety.

The European Commission estimates that car crash-related costs in Europe are around 160 billion euros, approximately 2% of the Gross Domestic Product [1]. In several countries, car crashes are the first cause of death among subjects aged 15-30, with a direct heavy impact on the years of life lost; in young subjects car crashes also represent one of the major causes of disability [2]. Several driver characteristics and driving behaviors due to age, diet, alcohol consumption, circadian rhythms, drug intake and diseases may contribute to a reduced alertness and induce drowsiness with dangerous consequences on driving ability thus increasing the risk of car crashes. It can be estimated that human factors concerning the psychophysical condition of the driver are involved in 60-80% of road accidents [2]. Crash involvement rates on a population basis are higher among males than females in all age groups [3]. This observation may be related to the fact that females drive fewer kilometres/year, drive mainly in town and for short journeys, rarely in bad weather and usually drive small engine cars. Males drive for a higher number of kilometres/year, on motorways for long distance driving and drive trucks or large engine cars. Most accidents involve subjects under 25 years (35%), whereas subjects aged over 70 years are involved in approximately 3% of car crashes, as expected considering that the percentage of drivers over 70 years of age is small compared to other age groups [3]. Taking into account the distance travelled (Fig. 1), crash rates in older subjects are higher than in the middle-aged and comparable to those of young subjects; crash rates in females are slightly higher than in males in all age groups [3]. Our study on truck drivers disclosed that the reaction times worsen (rS = 0.337; p = 0.034) and the number of correct answers decreases as age increases (rS = -0.354; p = 0.025) even in a limited age-range (Fig. 2) (unpublished data). Socioeconomic factors such as low social class and low educational level, family conditions (divorced or with divorced parents), job loss and social isolation and several behavioral and psychophysical factors are considered predisposing factors to traffic accidents [4]. Several psychotropic substances taken for recreational (alcohol and illicit drugs) or medical purposes can impair driving performance either by disturbing the information processing mental function, promoting risk taking behaviour, or by increasing response time [4]. Commonly administered therapeutic drugs, such as antihistaminics, antihypertensives, cardiac glycosides, diuretics, antidiabetic agents and antibiotics may cause BRIEF REVIEW