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Browsing Staff publications (SoE) by Author "af Wåhlberg, Anders E."
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Item Open Access Absence behavior as traffic crash predictor in bus drivers(Elsevier Science B.V., Amsterdam., 2009-12-31T00:00:00Z) af Wåhlberg, Anders E.; Dorn, LisaProblem: Various indicators of health have been shown to be associated with traffic crash involvement. As general health is also related to absence from work, the latter variable may be more strongly related to crashes, especially for professional drivers. Method: Bus driver absence from work was analyzed in association with their crash records. Two British samples and one Swedish sample were used. Results: One of the British samples yielded fair correlation between crash record and absence, while for the other the effect was restricted to the first three months of driving. The Swedish data had effects in the expected direction but these were not significant. Discussion: The use of an indirect, overall measurement of health, may be a viable method for predicting the traffic crash involvement for professional drivers, although replications are needed in larger samples and other populations. Impact on industry: The use of absence records for the identification of at risk drivers would seem to be a simple and useful method for companies with major fleets, and it also shows the importance of promoting employee health and well being at work as a potential method of reducing the cost, not only of absenteeism, but also of crashes in company vehicles.Item Open Access Bus accident record;The return of accident proneness(Taylor & Francis, 2009-02-28T00:00:00Z) af Wåhlberg, Anders E.; Dorn, LisaOne of the assumptions of the theory of accident proneness is that drivers’ accident liability is stable over time which was tested in the present paper. Previous investigations of this problem (or rather the conclusions) were found to be deficient, because they did not take into account the statistical problem of low variance in the accident variable. However, by correlating the between time periods association coefficient and the mean number of accidents across several samples, this problem can be overcome. Therefore, the stability of accident record over time was investigated in five samples of British bus drivers. It was found that the size of the correlations between time periods increased with the increase in mean accident frequency. Furthermore, this increase could be described by a linear regression line, which fit the various points extremely well. Also, the size of correlations of At fault accidents increased faster with the mean than did All accidents, although the latter had a higher initial value. It was therefore concluded, in contrast to previous authors, that the accident record of drivers is quite stable over time, and that the very low correlations which have often been found were due to the samples and methods used (low-risk drivers and short time periods equalling low crash means), and not of any inherent instability in drivers’ behaviour and/or accident record. It was also concluded that only culpable accidents should be used for this type of calculation. No evidence was found for a decrease in correlation size between single years' accidents when time periods between the years were lengthened, i.e. accidents in one year predicted accidents in several other years equally well. However, the period used was rather short. The results are discussed with reference to training intervention for accident–involved drivers, especially for organizations with major fleets such as bus compItem Open Access Culpable versus non-culpable traffic accidents; What is wrong with this picture?(Elsevier, 2007) af Wåhlberg, Anders E.; Dorn, LisaIt is often implicitly or explicitly assumed in traffic accident research that drivers with accidents designated as non-culpable are a random sample from the population. However, this assumption is dependent upon differences in the criterion used for culpability. If drivers are erroneously categorized by assuming randomness, results could be grossly misleading. The assumption of randomness leads to two predictions: first, no correlation should exist between culpable and non-culpable crashes; and second, the accident groups should differ on the variables known to be associated with accidents, such as amount of driving experience. These predictions were tested in two samples of bus drivers. It was found that in a sample with a harsh criterion (70% culpable accidents) for crash responsibility, the drivers with non-culpable accidents had the features expected, namely, they were more experienced for example, while in a sample with a lenient criterion (50 % culpable), this was not so. It was concluded that similar studies to the present one would need to be undertaken to establish exactly what percentage of drivers in a given population should be assigned culpable accidents, and construct a criterion that yields this ratio. Otherwise, the theoretical assumptions of randomness and non-responsibility will probably be violated to some degree.Item Open Access Development and validation of a self-report measure of bus driver behaviour(Taylor & Francis, 2010-12-01T00:00:00Z) Dorn, Lisa; Stephen, Lucy; af Wåhlberg, Anders E.; Gandolfi, JulieThere are likely to be individual differences in bus driver behaviour when adhering to strict schedules under time pressure. A reliable and valid assessment of these individual differences would be useful for bus companies keen to mitigate risk of crash involvement. This paper reports on three studies to develop and validate a self-report measure of bus driver behaviour. For study 1, two principal components analyses of a pilot questionnaire revealed six components describing bus driver behaviour and four bus driver coping components. In study 2, test-retest reliability of the components were tested in a sub-sample and found to be adequate. Further, the 10 components were used to predict bus crash involvement at three levels of culpability with consistently significant associations found for two components. For study 3, avoidance coping was consistently associated with celeration variables in a bus simulator, especially for a time-pressured drive. Statement of Relevance:The instrument can be used by bus companies for driver stress and fatigue management training to identify at-risk bus driver behaviour. Training to reduce the tendency to engage in avoidance coping strategies, improve evaluative coping strategies and hazard monitoring when under stress may improve bus driver safety.Item Open Access The effect of social desirability on self reported and recorded road traffic accidents(Elsevier Science B.V., Amsterdam., 2010-03-31T00:00:00Z) af Wåhlberg, Anders E.; Dorn, Lisa; Kline, T.The use of lie scales has a fairly long history in psychometrics, with the intention of identifying and correcting for socially desirable answers. This represents one type of common method variance (bias introduced when both predictors and predicted variables are gathered from the same source), which may lead to spurious associations in self-reports. Within traffic safety research, where self-report methods are used abundantly, it is uncommon to control for social desirability artifacts, or reporting associations between lie scales, crashes and driver behaviour scales. In the present study, it was shown that self-reports of traffic accidents were negatively associated with a lie scale for driving, while recorded ones were not, as could be expected if the scale was valid and a self-report bias existed. We conclude that whenever self-reported crashes are used as an outcome variable and predicted by other self-report measures, a lie scale should be included and used for correcting the associations. However, the only existing lie scale for traffic safety is not likely to catch all socially desirable responding, because traffic safety may not be desirable for all demographic groups. New lie scales should be developed specifically for driver behaviour questionnaires, to counter potential bias and artifactual results. Alternatively, the use of a single source of data should be discontinued. (C) 2009 Elsevier Ltd. All rights reserved.Item Open Access The Manchester Driver Behaviour Questionnaire as predictor of road traffic accidents(Taylor & Francis, 2011-02-28T00:00:00Z) af Wåhlberg, Anders E.; Dorn, Lisa; Kline, T.The Driver Behaviour Questionnaire (DBQ) has mainly been used as predictor of self-reported road traffic accidents. The associations between crashes and the violation and error factors of the DBQ however, may be spuriously high due to reporting bias. In the present study, the DBQ was tested as predictor of self- reported and recorded accidents in four samples of private and professional drivers. The findings show that the DBQ scale only predicts self-reported accidents, not recorded crashes, despite the higher validity of company data, and the higher means of the recorded data across these samples. The results can be explained by a common method variance bias. In our review of the DBQ research, the use of the instrument was found to be heterogeneous concerning the number of items, scales used, and factor analytic methods applied. Thus, the DBQ may not be as homogenous and as successful in predicting accidents as is often claimed.Item Open Access Work-related road safety: An analysis based on U.K. bus driver performance(Blackwell Publishing Ltd, 2008-02-28T00:00:00Z) Dorn, Lisa; af Wåhlberg, Anders E.The effects of age and experience on accident involvement for bus drivers were investigated, with special emphasis upon the first years of being an operator, using two methods. First, direct calculations between these variables were undertaken. Thereafter, a variant of the method of quasi-induced exposure (a ratio of culpable versus nonculpable accidents in the population) was used and referred to as the indirect method. These methods yielded fairly similar results, given that the samples used were drawn from the same population but only partly overlapping. It was found that experience had the strongest effect on accidents in the first year of driving, while age had a u-shaped association with accidents, that is, young and old drivers had more accidents, something that was more apparent when experience was held constant. These results show that, for bus drivers, experience is initially more important than age, but after two or three years, the effect is small. Thereafter, age is the more discernible variable, although it is a very weak factor in predicting crash risk.