Browsing by Author "Dorn, Lisa"
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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 Accident proneness of bus drivers; controlling for exposure(Taylor and Francis, 2020-04-19) Dorn, Lisa; af Wåhlberg, Anders E.It is argued that the reason that previous evidence apparently did not support the accident proneness hypothesis was faulty methodology and erroneous interpretations of results. Between time periods correlations of traffic accident records actually show an impressive stability over time when restriction of variance is controlled for. However, stability can be caused by stable differences in exposure. Correlations of accident records between time periods were analysed comparing full time and part-time bus drivers. For drivers who worked full time, the amount of exposure was held semi-constant while part-time drivers could be expected to work differing hours. If differential exposure causes stability in crash record, then part-time drivers should yield stronger correlations between time periods for crashes compared with full-time drivers. Between time periods accident correlations for part-time drivers were weaker than the corresponding ones for full time drivers. Correlations increased with increasing variance in the data. Results for all crashes fit in well with other meta-data, while culpable crashes did not, probably due to faulty coding. The current results support the notion of the tendency to cause traffic accidents as a stable trait within individuals as this is apparently not caused by stable differences in exposure.Item Open Access Behavioural culpability for traffic accidents(Elsevier, 2018-12-03) Dorn, Lisa; af Wåhlberg, Anders E.This study presents a description of the concept of behavioural culpability, a step-by-step manual for using it, and an empirical test of a suspected mis-classification of culpability. Behavioural culpability is defined as whether the driver’s actions contributed to a crash and that non-culpable crashes are not caused by any specific behaviour and can only be predicted from exposure. Drivers with non-culpable crashes are therefore a random sample of the population. However, if the criteria for culpability and/or the individual judgements are not reflective of the principle of behavioural culpability, no fault drivers will not be a random sample of the driving population. To test the predictions from the definition of randomness in a sample assumed to have sub-optimal coding, the categorization of crash involvement undertaken by a British bus company was tested for associations between at fault and no fault crashes, age and experience. As predicted from the low percentage of at fault accidents in the sample, correlations between the variables indicated that a fair percentage of at fault crashes had been coded as no fault of the bus driver, suggesting a too lenient criterion. These results show that within fleet-based companies, culpability for a crash is probably allocated for legal reasons, which means that the predictability of accident involvement taking into account individual differences is not fully utilized. The aim of behavioural culpability coding is to increase effect sizes in individual differences in safety research and to improve our capability of predicting accident involvement.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 Bus driver accident record; stability over time, exposure and culpability(Taylor & Francis, 2019-05-28) af Wåhlberg, Anders E.; Dorn, LisaThe tendency for drivers to have a stable accident record over time was tested in a population of bus drivers. Analyses included investigations of the effects of responsibility for the crash, exposure and length of time period, on stability. All associations between numbers of accidents for individuals in different short time periods were found to be weak, but longer time periods increased the size of the correlations. Restricting the analyses to include only those crashes for which the drivers were deemed responsible had a slightly negative effect on correlations. However, this was due to lower means (and thus variance) in these calculations. Similarly, controlling for hours worked decreased the correlations somewhat, but this was due to an outlier problem. The results are consistent with previous research and indicate that stability of accident involvement exists and that the effects can be reliably found under certain methodological circumstances. The sizes of coefficients are determined mainly by the restriction of variance, not by any underlying lack of stability. The stable tendency to cause mishaps within the same environment is a strong factor in traffic safety although this is not apparent when variance in the data is low.Item Open Access Bus drivers who leave: were they more crash-involved?(Elsevier, 2018-12-06) af Wåhlberg, Anders E.; Dorn, LisaTurnover is usually considered to be a safety problem for companies, but can also be an advantage, if those who leave are less safe than those who stay. This problem has rarely been investigated for bus drivers, where the financial and human costs of crashes are high. This study tested whether bus drivers who left their jobs had more crashes than those who remained, using company records. Several analyses were run, using crashes per number of days worked, the absolute number of crashes in a specific time period, as well as the ratio of culpable to non-culpable crashes. Drivers who left the company, except those who retired, had forty percent more crashes than those who stayed, but were also less experienced, which explained part of the difference. Results were similar regardless of analysis performed. Turnover may be a problem for bus companies due to the costs of recruitment and training, but this study suggests that there are benefits for turnover too. Fleet-based companies would probably gain more by improving driver selection methods than trying to retain drivers with a high crash rate, as a natural selection process seems to lead to the safest drivers staying with the company.Item Open Access A cluster randomised controlled trial (cRCT) evaluation of a pre-driver education intervention using the Theory of Planned Behaviour(Elsevier, 2023-03-14) Box, Elizabeth; Dorn, LisaRoad traffic injuries are the leading of cause of death of 5–29-year-olds worldwide (World Health Organisation, 2018) making young driver safety a global public health concern. Pre-driver road safety education programmes are popular and commonly delivered with the aim of improving safety amongst this at risk group but have rarely been found to be effective (Kinnear, Lloyd, Helman, Husband, Scoons, Jones et al., 2013). A pre-driver education intervention (DriveFit) was designed and evaluated with a cluster randomised controlled trial (cRCT) using the Theory of Planned Behaviour (TPB) (Ajzen, 1991). The responses of 16–18-year-old students (n = 437) from 22 schools/colleges in Devon, UK were analysed and showed that the DriveFit intervention led to some small improvements in risk intentions, attitudes, and other measures, which differed by sub-group. Speed intentions improved immediately post- intervention (T2), whereas a composite measure of all intentions and mobile phone use intentions improved at 8–10 weeks post-intervention (T3). Apart from speed intentions, a trend towards intentions becoming safer at T3 was noted. Mobile phone use and speeding attitudes, a composite measure of attitudes, as well as attitudes to driving violations and perceptions of risk, improved at T2 and T3, with the size of the effect slightly reduced at T3. Participants expressed safe views at baseline (T1), which overall left minimal room for improvement. Whilst previous research has found that education interventions deliver small self-reported effects, that diminish over time (i.e., Poulter and McKenna, 2010), this study finds small, but lasting attitude effects (which diminish in magnitude over time) and a trend towards improving intentions, over and above the control group. The findings provide some guidance on future research to design and evaluate educational interventions for pre- and novice drivers.Item 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 Design and Development of a Bus Simulator for Bus Driver(Cranfield University, 2006) Muncie, Helen; Dorn, LisaThe bus industry is plagued by high accident costs and risks of passenger injuries. A bus simulator may offer a method of reducing accident rates by delivering targeted training to bus drivers who are most at risk. The first part of this thesis describes the design of the UK's first bus simulator, the fidelity of which was based on a thorough analysis of bus crashes. The second part describes the first studies in a multi-staged method to evaluate the training effectiveness of the simulator: face validity, effects of bus driver experience and stress on simulated performance and simulator sickness. This approach ensured that the ABS has a reasonable level of fidelity, is capable of eliciting behaviourally valid responses from bus drivers and is the first step is achieving training transfer effectiveness. The final study investigated the occurrence of self-bias in bus drivers. The conclusions drove the design of simulated scenarios to be used for bus driver training. Keywords: Bus, Simulator, Fidelity, Validity, Accidents, Driving, Stress, TrainingItem Open Access The Development and application of a bespoke organisational learning competency framework in a global organisation(Cranfield University, 2004-01) Tarrini, Mauro G.; Dorn, LisaOrganisational Learning has been conceptualised and measured in various ways. The two studies reported in this thesis sought to take a new, bespoke approach to Organisational Learning in a global air transport company undergoing substantial organisational and strategic change. The research sought to develop a bespoke competency framework of Organisational Learning and apply it within the organisation to investigate employees' perceptions of the Organisational Learning climate. The research applied both qualitative and qualitative methods: semi-structured interviews and a 68-item self-completion questionnaire survey. Factor Analysis yielded a clear, conceptually sound six-factor solution. Organisational Learning climate perceptions were compared across occupational, departmental and geographical subgroups. The results indicated that there were no statistically significant occupational or geographical differences in perceptions of the Organisational Learning climate although some departmental differences were observed. The relationaship between perceived Organisational Learning climate and organisational commitment was explored and a clear link between them was found.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 Development of a psychometric measure of police driver risk(Cranfield University, 2007) Gandolfi, Julie; Dorn, LisaCollisions involving police vehicles or occurring as a result of police activity resulted in over 2000 casualties and 31 deaths in England and Wales in 2003-4. The assessment of police driver risk is currently restricted to subjective evaluations carried out by members of each force's police driver training team. Objective risk assessments are becoming increasingly popular with private companies operating fleets of vehicles, in an attempt to target training interventions at the drivers who are most at risk of collision involvement. This thesis reports the development of a psychometric measure of police driver risk using a series of qualitative and quantitative methods. The Driver Stress Inventory (DSI) was administered to 302 police drivers to establish its suitability as a basis on which to build the Police Driver Risk Index (PDRI). The Driver Stress Inventory is a well-established psychometric measure of driver stress, which consists of five behavioural factors and five coping factors. The DSI factor structure was largely replicated for the police sample. The generation of new police-specific items was facilitated by a series of in-depth semi- structured interviews with standard and advanced police drivers. The transcripts were analysed for common themes and items were generated from this analysis. The new PDRI was administered to a sample of 333 police drivers, and a Principal Components Analysis was carried out in order to establish the new factor structure and identify items contributing to the risk profile. Further refinement was carried out using an Item Discrimination Analysis, which allowed the length of the test to be reduced further. The effects of demographic and situational data on PDRI factor scores was investigated, and group differences were reported for age, sex, driving experience, and collision involvement. Test-retest reliability was investigated and a validation study using observational data, driver self-assessment and trainer assessment was carried out. The Police Driver Risk Index will be used to identify drivers at «highest risk of involvement in a collision, and pinpoint the areas in which they require remedial training. This will allow police forces to target their driver training resources more effectively.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 effects of driver training on simulated driving performance(Elsevier Science, 2005-01) Dorn, Lisa; Barker, D.Given that the beneficial effects of driver training on accident risk may not be an appropriate criterion measure, this study investigates whether professionally trained and experienced drivers exhibit safer driving behaviour in a simulated driving task compared with drivers without professional driver training. A sample of 54 police trained drivers and a sample of 56 non-police trained drivers were required to complete two tasks. Firstly to overtake a slow-moving bus on a hazardous stretch of single-lane road with bends and hills and secondly to follow a lead vehicle travelling at 55 mph in a built-up section with a speed limit of 30 mph. Results showed that in comparison with non-police trained drivers, police drivers were significantly less likely to cross the central division of the road at unsafe locations during the overtaking task and reduced their speed on approach to pedestrians at the roadside in the following task to a greater extent. Police drivers also adopted a more central lane position compared with non-police trained drivers on urban roads and at traffic lights during the following task. Driver group differences in simulated driving performance are discussed with reference to the implications for driver training assessment and skill development.Item Open Access The effects of Electronic Stability Control (ESC) on fatal crash rates in the United States(Elsevier, 2023-12-21) af Wåhlberg, Anders; Dorn, LisaProblem: Electronic Stability Control (ESC) is believed to be among the most efficient vehicle safety interventions with reported effects around 50% for fatal single and rollover crashes. However, such estimates have used sample data, which have not controlled for the possibilities of self-selection, behavioral adaptation, increased access to the technology by less safe drivers, and the calculation of effects on very specific categories of crashes. Effects of ESC in the population can therefore be expected to be smaller than is currently believed. Method: National U.S. data for fatal crashes, driving exposure and other control factors, and market penetration of ESC over 1991–2021 were used to calculate whether the trends in fatalities over time in crash rates for singles, rollovers, and fatal crashes in general matched projections from estimates of effectiveness. Results: It was found that downward trends in the relevant crash types were generally present before ESC was introduced, and that the trends thereafter were weaker. Although some trends were consistent with effects of ESC, they were markedly smaller than the projected ones, and could be explained by other factors such as the number of vehicles per capita. At best, the effect for rollovers could be up to two-thirds of previous estimates, no effect was detected for singles, while for all fatal crashes results depended upon the type of analysis performed. These results conflict with conclusions in all published ESC crash sample studies, which have compared vehicles with and without ESC. This discrepancy can be explained by methodological errors in the previous studies using induced exposure methods and self-selected samples. Practical applications: Traffic safety may not be as much improved by technological interventions as believed. Alternative approaches to traffic safety are needed, which do not rely on technology that interferes with driver behavior.Item Open Access Experience as a safety factor in driving; Methodological considerations in a sample of bus drivers(MDPI, 2019-06-13) af Wåhlberg, Anders E.; Dorn, LisaExperience is generally seen as an important factor for safe driving, but the exact size and details of this effect has never been meta-analytically described, despite a fair number of published results. However, the available data is heterogeneous concerning the methods used, which could lead to very different results. Such method effects can be difficult to identify in meta-analysis, and a within-study comparison might yield more reliable results. To test for the difference in effects between some different analytical methods, analyses of data on bus driver experience and crash involvement from a British company were conducted. Effects of within- and between-subjects analysis, non-linearity of effects, and direct and induced exposure methods were compared. Furthermore, changes in the environmental risk were investigated. Between-subject designs yielded smaller effects as compared to within-subjects designs, while non-linearity was not found. The type of exposure control applied had a strong influence on effects, as did differences in overall environmental risk between years. Apparently, “the effect of driving experience” means different things depending upon how calculations have been undertaken, at least for bus drivers. A full meta-analysis, taking several effects of methodology into account, is needed before it can be said that the effect of driving experience on crash involvement is well understood.Item Open Access How reliable are self-report measures of mileage, violations and crashes?(Elseveir, 2015-03-12) af Wåhlberg, Anders E.; Dorn, LisaThe use of self-reported driver mileage, violations and crashes is very popular in traffic safety research, but their validity has been questioned. One way of testing validity is with an analysis of test–retest reliability. Three mechanisms might influence reliability in self report; actual changes in the variable over time, stable systematic reporting bias, and random error. Four samples of drivers who had responded twice to an online questionnaire asking them to report their mileage, violations and crashes were used and correlations between self reports for this data were calculated. The results for crashes were compared to expected correlations, calculated from the error introduced by the non-overlapping periods and the variable means. Reliability was fairly low, and controlling for mileage in the violations and crashes calculations did not strengthen the associations. The correlation between self reports of crashes in different time periods was found to be much larger than expected in one case, indicating a report bias, while the other correlation agreed with the predicted value. The correlations for overlapping time periods were much smaller than expected. These results indicate that drivers’ self reports about their mileage, violations and crashes are very unreliable, but also that several different mechanisms are operating. It is uncertain exactly under what circumstances different types of self report bias is operating. Traffic safety researchers should treat the use of self-reported mileage, violations and crashes with extreme caution and preferably investigate these variables with the use of objective data.Item Open Access Making sense of invulnerability at work—a qualitative study of police drive(Elsevier Science B.V., Amsterdam., 2003-12-01T00:00:00Z) Dorn, Lisa; Brown, BThis paper reports a qualitative study of 54 police drivers who were interviewed about their views on police driver training, driving strategies and their accident involvement. Study of the transcribed interviews indicated that officers constructed narratives of themselves as being highly aware of hazards presented by other road users and they used a variety of discursive devices to minimise their own culpability and attribute risk elsewhere. Rather than maintaining a straightforward ‘illusion of invulnerability’ they were formulating a ‘topography of risk’ in which they were responding to hazards presented by suspects or other road users. Their meticulously detailed accounts of the circumstances surrounding accidents serve to place them as knowledgeable and impartial participants and create a sense of expertise and authority. Training initiatives could profitably seek to challenge this ‘topography of risk’ and sense of authority so that drivers more fully appreciate the hazard they may present to themselves andItem 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 Professional Driver Training and Driver Stress: Effects on Simulated Driving Performance(Elsevier, 2005) Dorn, Lisa