Driver Characteristics and Crash Involvement: the evidence base
Recruitment and Selection
In this excerpt from our ‘How to Select Safe Drivers’ white paper, Dr Lisa Dorn outlines the research conducted into driver characteristics and crash involvement, whilst driving for work:
Early work to investigate the characteristics of drivers who are less likely to be involved in a crash was an important topic for Industrial Psychologists working in the 50’s and 60’s. Studies found that certain personality traits influenced safety behind the wheel and these traits were found to be related to traffic violation and crash rates. Tillman and Hobbs (1949) used direct observations, psychiatric interviews, police records, juvenile court records etc. as part of a study of high crash involved taxi drivers and low crash involved taxi drivers. The characteristics of the high crash involved group included aggressiveness, impulsiveness, inability to delay gratification, exhibitionistic tendencies, projection of blame and serious problems with authority. Similarly, a later study by Conger et al (1959) found that personality factors predicted those that were categorised in high and low crash groups with an accuracy of 73%.
High crash involved drivers displayed significantly more impulsivity, aggressive behaviour, low tolerance for tension, extremes of egocentricity and emotional lability. Haner (1961) used a 300-question personality inventory in assigning insurance premium risks to 4,000 male drivers under age 25. By obtaining profiles of frustration and aggressiveness, impulsiveness, and acceptance of social responsibility via psychometrics, the insurance company predicted accident frequency with great accuracy. Nearly 90% of license revocations for traffic violations involved drivers being assigned to the highest risk category based on the results of the psychometric tests of personality.
Since then, studies of traffic crashes amongst professional drivers have consistently shown that personality-based attributes play an important role in predicting crash involvement, suggesting it is possible that to distinguish between safe and unsafe professional drivers. In a pioneering study, Burns and Wilde (1995) showed that a ‘High Risk Personality’ profile (i.e., need for tension, risk and adventure) was associated with speeding and careless driving among professional drivers, whereas excitement seeking was related to traffic rule violation. Sümer (2003) showed that, among different groups of professional drivers, depression symptomatology, anxiety, hostility and psychoticism predicted crashes based on violations and errors observed. The study also showed that excitement seeking was associated with higher speeds and driver aggression. More recently, studies have focused on the impact of single personality dimensions on risky driving behaviour (Dahlen et al, 2005; Taubman-Ben-Ari and Yehiel, 2012), while others estimated the risk for traffic crashes using multivariate combination of different personality based emotional dimensions (Dorn et al, 2010).
Driver Stress Dimensions: The Cranfield Studies
High crash rates and poor driving performance amongst drivers at work have been attributed to vulnerability to driver stress and fatigue according to research at Cranfield University. Driver stress is related to how the driver appraises the driving task and traffic environment. If the driver appraises the demands as exceeding their capability or resources, the resultant stress can impair driving performance. This is the case for overload as well as underload conditions such as driving on monotonous motorway journeys. Cranfield studies have shown that driving commercial vehicles is a highly stressful occupation with mood being associated with acceleration behaviour; switching off from the driving task; adopting poor safety margins and speed. Fatigue has also been found to be associated with poor vehicle control and leaving less time to react to potential hazards (Dorn, 2005; Dorn et al, 2010).
The Cranfield studies found that there are individual differences in how commercial drivers adapt their driving style to cope with traffic conditions. Drivers that employ more effective coping strategies compensate for the negative impact of stress and fatigue. New drivers however, are at a particularly high level of risk given that they have not had the opportunity to acquire sufficient experience of operational driving. New drivers may also not have developed good coping strategies for dealing with driver stress and fatigue. This can be illustrated with Cranfield studies showing that novice commercial drivers have a significantly higher crash risk (Dorn, Muncie and Garwood, 2005). Crash involved novice commercial drivers use more ineffective coping strategies than crash-free bus drivers (Dorn and Garwood, 2004; Dorn et al, 2010).