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  • 1. Ahlström, Christer
    et al.
    Anund, Anna
    Fors, Carina
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Karolinska Institute, Sweden.
    Effects of the road environment on the development of driver sleepiness in young male drivers2018In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 112, p. 127-134Article in journal (Refereed)
    Abstract [en]

    Latent driver sleepiness may in some cases be masked by for example social interaction, stress and physical activity. This short-term modulation of sleepiness may also result from environmental factors, such as when driving in stimulating environments. The aim of this study is to compare two road environments and investigate how they affect driver sleepiness. Thirty young male drivers participated in a driving simulator experiment where they drove two scenarios: a rural environment with winding roads and low traffic density, and a suburban road with higher traffic density and a more built-up roadside environment. The driving task was essentially the same in both scenarios, i.e. to stay on the road, without much interaction with other road users. A 2 x 2 design, with the conditions rural versus suburban, and daytime (full sleep) versus night-time (sleep deprived), was used. The results show that there were only minor effects of the road environment on subjective and physiological indicators of sleepiness. In contrast, there was an increase in subjective sleepiness, longer blink durations and increased EEG alpha content, both due to time on task and to night-time driving. The two road environments differed both in terms of the demand on driver action and of visual load, and the results indicate that action demand is the more important of the two factors. The notion that driver fatigue should be countered in a more stimulating visual environment such as in the city is thus more likely due to increased task demand rather than to a richer visual scenery. This should be investigated in further studies.

  • 2. Anund, Anna
    et al.
    Fors, Carina
    Ihlstrom, Jonas
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Radboud University, The Netherlands.
    An on-road study of sleepiness in split shifts among city bus drivers2018In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 114, p. 71-76Article in journal (Refereed)
    Abstract [en]

    Bus drivers often work irregular hours or split shifts and their work involves high levels of stress. These factors can lead to severe sleepiness and dangerous driving. This study examined how split shift working affects sleepiness and performance during afternoon driving. An experiment was conducted on a real road with a specially equipped regular bus driven by professional bus drivers. The study had a within-subject design and involved 18 professional bus drivers (9 males and 9 females) who drove on two afternoons; one on a day in which they had driven early in the morning (split shift situation) and one on a day when they had been off duty until the test (afternoon shift situation). The hypothesis tested was that split shifts contribute to sleepiness during afternoon, which can increase the safety risks. The overall results supported this hypothesis. In total, five of the 18 drivers reached levels of severe sleepiness (Karolinska Sleepiness Scale 8) with an average increase in KSS of 1.94 when driving in the afternoon after working a morning shift compared with being off duty in the morning. This increase corresponded to differences observed between shift workers starting and ending a night shift. The Psychomotor Vigilance Task showed significantly increased response time with split shift working (afternoon: 0.337 s; split shift 0.347 s), as did the EEG-based Karolinska Drowsiness Score mean/max. Blink duration also increased, although the difference was not significant. One driver fell asleep during the drive. In addition, 12 of the 18 bus drivers reported that in their daily work they have to fight to stay awake while driving at least 2-4 times per month. While there were strong individual differences, the study clearly showed that shift working bus drivers struggle to stay awake and thus countermeasures are needed in order to guarantee safe driving with split shift schedules.

  • 3. Dawson, Drew
    et al.
    Ian Noy, Y.
    Härmä, Mikko
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Belenky, Gregory
    Modelling fatigue and the use of fatigue models in work settings2011In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 43, no 2, p. 549-564Article in journal (Refereed)
    Abstract [en]

    In recent years, theoretical models of the sleep and circadian system developed in laboratory settings have been adapted to predict fatigue and, by inference, performance. This is typically done using the timing of prior sleep and waking or working hours as the primary input and the time course of the predicted variables as the primary output. The aim of these models is to provide employers, unions and regulators with quantitative information on the likely average level of fatigue, or risk, associated with a given pattern of work and sleep with the goal of better managing the risk of fatigue-related errors and accidents/incidents. The first part of this review summarises the variables known to influence workplace fatigue and draws attention to the considerable variability attributable to individual and task variables not included in current models. The second part reviews the current fatigue models described in the scientific and technical literature and classifies them according to whether they predict fatigue directly by using the timing of prior sleep and wake (one-step models) or indirectly by using work schedules to infer an average sleep-wake pattern that is then used to predict fatigue (two-step models). The third part of the review looks at the current use of fatigue models in field settings by organizations and regulators. Given their limitations it is suggested that the current generation of models may be appropriate for use as one element in a fatigue risk management system. The final section of the review looks at the future of these models and recommends a standardised approach for their use as an element of the 'defenses-in-depth' approach to fatigue risk management.

  • 4. Di Milia, Lee
    et al.
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    The distribution of sleepiness, sleep and work hours during a long distance morning trip: A comparison between night- and non-night workers2013In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 53, p. 17-22Article in journal (Refereed)
    Abstract [en]

    Few studies have examined the extent of driver sleepiness during a long distance morning trip. Sleepiness at this time may be high because of night work, waking early to commence work or travel, sleep disorders and the monotony of driving long distances. The objective of this study was to estimate the prevalence of chronic sleepiness (Epworth sleepiness score ≥10) and sleep restriction (≤5h) in a sample of 649 drivers. Participants driving between 08:00 and 10:00 on three highways in regional Australia participated in a telephone interview. Approximately 18% of drivers reported chronic sleepiness. The proportions of night workers (NW) and non-night workers (NNW) with chronic sleepiness were not significantly different but males reported a significantly greater proportion of chronic sleepiness than females. The NW group had a significantly greater proportion of drivers with ≤5h of sleep in the previous 24 and 48h, fewer nights of full sleep (≤4), acute sleepiness and longer weekly work hours. The NW group reported driving a significantly longer distance at Time 1 (Mean=140.29±72.17km, versus 117.55±89.74km) and an additional longer distance to complete the journey (Mean=89.33±95.23km, versus 64.77±94.07km). The high proportions of sleep restriction and acute sleepiness among the NW group, and the amount of chronic sleepiness in the NW and NNW groups reported during a long distance morning trip may be of concern for driver safety.

  • 5.
    Falk, Birgitta
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Do drivers become less risk-prone after answering a questionnaire on risky driving behaviour?2010In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 42, no 1, p. 235-244Article in journal (Refereed)
    Abstract [en]

    Two studies showed that answering a questionnaire regarding self-reported risky driving behaviour and attitudes led to a significant (p < 0.001) decrease in self-reported risky driving behaviour at a follow-up some five weeks after answering the first questionnaire. In Study I participants (193 men, 18-20 years old) also reported more concern about hurting others, increased subjective probability of accidents, but less thinking about injuries at follow-up. In Study 2 (149 men, 18-19 years old) effects on attitudes at follow-up were not tested. The results are discussed in terms of the question-behaviour effect, that is, questioning a person about a certain behaviour can influence his future performance of that behaviour. Assuming that most young male drivers essentially disapprove of traffic violations, it is argued that answering the questionnaire served as an intervention that made attitudes more accessible and led to a polarization towards stronger disapproval of traffic violations, which in turn influenced reported risky driving behaviour. The need to develop alternative instruments for evaluating effects of experimental traffic safety interventions is also discussed.

  • 6.
    Hallvig, David
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Anund, Anna
    Fors, Carina
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Karlsson, Johan G.
    Wahde, Mattias
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Sleepy driving on the real road and in the simulator-A comparison2012In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 50, p. 44-50Article in journal (Refereed)
    Abstract [en]

    Sleepiness has been identified as one of the most important factors contributing to road crashes. However, almost all work on the detailed changes in behavior and physiology leading up to sleep related crashes has been carried out in driving simulators. It is not clear, however, to what extent simulator results can be generalized to real driving. This study compared real driving with driving in a high fidelity, moving base, driving simulator with respect to driving performance, sleep related physiology (using electroencephalography and electrooculography) and subjective sleepiness during night and day driving for 10 participants. The real road was emulated in the simulator. The results show that the simulator was associated with higher levels of subjective and physiological sleepiness than real driving. However, both for real and simulated driving, the response to night driving appears to be rather similar for subjective sleepiness and sleep physiology. Lateral variability was more responsive to night driving in the simulator, while real driving at night involved a movement to the left in the lane and a reduction of speed, both of which effects were absent in the simulator. It was concluded that the relative validity of simulators is acceptable for many variables, but that in absolute terms simulators cause higher sleepiness levels than real driving. Thus, generalizations from simulators to real driving must be made with great caution.

  • 7. Sallinen, Mikael
    et al.
    Sihvola, Maria
    Puttonen, Sampsa
    Ketola, Kimmo
    Tuori, Antti
    Härmä, Mikko
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Åkerstedt, Torbjörn
    Karolinska Institute, Sweden.
    Sleep, alertness and alertness management among commercial airline pilots on short-haul and long-haul flights2016In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 98, p. 320-329Article in journal (Refereed)
    Abstract [en]

    Airline pilots' sleep and on-duty alertness are important focus areas in commercial aviation. Until now, studies pertaining to this topic have mainly focused on specific characteristics of flights and thus a comprehensive picture of the matter is not well established. In addition, research knowledge of what airline pilots actually do to maintain their alertness while being on duty is scarce. To address these gaps in research knowledge, we conducted a field study on a representative sample of the airline pilots of a medium-sized airline. The sample consisted of 90 pilots, of whom 30 flew long-haul (LH) routes, 30 short-haul (SH) routes, and 30 flew both. A total of 86 pilots completed the measurements that lasted for almost two months per pilot. The measurements resulted in a total of 965 flight duty periods (FDPs) including SH flights and 627 FDPs including LH flights. During the measurement periods, sleep was measured by a diary and actigraphs, on-duty alertness by the Karolinska Sleepiness Scale (KSS) in all flight phases, and on-duty alertness management strategies by the diary. Results showed that SH and LH FDPs covering the whole domicile night (00:00-06:00 at home base) were most consistently associated with reduced sleep-wake ratio and subjective alertness. Approximately every 3rd FDP falling into this category involved a reduced sleep-wake ratio (1:3 or lower) and every 2nd a reduced level of subjective alertness (KSS rating 8-9 in at least one flight phase). The corresponding frequencies for the SH and LH FDPs that partly covered the domicile night were every 10th and every 5th FDP and for the pure non-night FDPs every 30th and every 36th FDP, respectively. The results also showed that the pilots tended to increase the use of effective on-duty alertness management strategies (consuming alertness-promoting products and taking strategic naps) in connection with the FDPs that overlapped the domicile night. Finally, the results showed that the frequency of flights involving reduced subjective alertness depended on how alertness was assessed. If it was assessed solely in the flight phase just before starting the landing procedures (top of descent) the phenomenon was less frequent than if the preceding cruise phase was also taken into account. Our results suggest that FDPs covering the whole domicile night should be prioritised over the other FDPs in fatigue management, regardless of whether an FDP is a short-haul or a long-haul. In addition, the identification of fatigue in flight operations requires one to assess pilots' alertness across all flight phases, not only at ToD. Due to limitations in our data, these conclusions can, however, be generalise to only LH FDPs during which pilots can be expected to be well acclimatised to the local time at their home base and SH night FDPs that include at least 3h of flying in the cruise phase.

  • 8. Summala, Heikki
    et al.
    Rajalin, Sirpa
    Radun, Igor
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. University of Helsinki, Finland.
    Risky driving and recorded driving offences: A 24-year follow-up study2014In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 73, p. 27-33Article in journal (Refereed)
    Abstract [en]

    Permanent individual differences in driver behavior and accident risk have long been under active debate. Cognitive and personality factors have correlated with risky driving indicators in cross-sectional studies, and prospective cohort studies are now increasingly revealing early antecedents of risky behavior and injury mortality in adult age, with connections to stable personality traits. However, long-term stability in driver behavior or accident involvement has not been documented in a general driver population.This study reports 24-year follow-up data from a study that compared the recorded offenses between 134 drivers stopped by the police because of sustained risky driving and 121 control drivers stopped at the same locations at the same time in 1987 (Rajalin, 1994. Accid. Anal. Prev., 26, 555-562). Data were compiled from national driver records and accident statistics for the same drivers again 24 years later, and their yearly mileage and speed behavior was requested in a mail survey. The results showed that the two groups of drivers sampled on one trip a quarter of a century ago still differ from each other. The offenders still have more entries in their driver record, also when adjusted for age and mileage (OR=1.59, CI=1.03-2.46), they still report in the survey that they drive faster and overtake other cars more often. The results show that individual differences in driver behavior persist for decades, perhaps for life. However, in this on-road sample, the effect seems to be moderated by occupation which also presumably explains the lower mortality among the offenders during this 24-year follow-up.

  • 9.
    Svenson, Ola
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Psychology. Decision Research, Oregon, USA.
    Eriksson, Gabriella
    Gonzalez, Nichel
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Braking from different speeds: Judgments of collision speed if a car does not stop in time2012In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 45, p. 487-492Article in journal (Refereed)
    Abstract [en]

    The purpose of speed limits is to keep driving speed low enough for drivers to be able to pay attention to relevant information and timely execute maneuvers so that the car can be driven in a safe way and stopped in time. If a driver violates a speed limit or drives too fast she or he will not be able to stop as quickly as from a slower speed. We asked participants to imagine that they themselves had driven a car outside a school at a speed of 30 km/h when a child suddenly had rushed into the street. From this speed it was possible to stop the car just in front of the child after braking as quickly and forcefully as possible. We then asked the participants to imagine that they drove the same street at a higher speed of 50 km/h and the child appeared at the same place as before. At what speed would the car hit the child after braking in the same way as before? This kind of problems were presented in three studies and the results showed that the judged speeds of collision were always underestimated in different hypothetical driving context scenarios by judges differing in numerical skills. This indicates an overly optimistic view on the possibilities to reduce speed quickly if the driving speed is too fast, which is an important component of attitudes towards speed limits, their legitimacy and recommended driving speeds. Further implications of the results were discussed last.

  • 10.
    Svenson, Ola
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Psychology. Decision Research, Eugene, OR 97 401, USA.
    Eriksson, Gabriella
    Swedish National Road and Transport Research Institute, Linköping, Department of Behavioural Sciences, Linköping University.
    Mertz, C. K.
    Department of Behavioural Sciences, Linköping University.
    Debiasing overoptimistic beliefs about braking capacity2013In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 58, p. 75-80Article in journal (Refereed)
    Abstract [en]

    We investigated, using questionnaires, different strategies for removing drivers’ overoptimism (Svenson et al., 2012a) about how fast their speed could be decreased when they were speeding compared with braking at the speed limit speed. Three different learning groups and a control group made collision speed judgments. The first learning group had the distance a car travels during a driver's reaction time for each problem. The second group had this information and also feedback after each judgment (correct speed). The third group judged collision speed but also braking distance and received correct facts after each problem. The control group had no information at all about reaction time and the distance traveled during that time. The results suggested the following rank order from poor to improved performance: control, group 1, group 3 and group 2 indicating that information about distance driven during a driver's reaction time improved collision speed judgments and that adding stopping distance information did not add to this improvement.

  • 11.
    Svenson, Ola
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Salo, Ilkka
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Effects of speed limit variation on judged mean speed of a trip2010In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 42, no 2, p. 704-708Article in journal (Refereed)
    Abstract [en]

    Three experiments were set up to study how drivers estimate mean travel speeds on trips with different speed limits. To specify, participants judged mean speeds of trips with speed limits on different distances of the trip. Study I showed that the mean speed on a road with a temporary 30km/h speed limit was overestimated if the speeds were greater than 80km/h on the rest of the trip. Study 2 replicated and extended the results to problems with more speed combinations. In Study 3 the distances of the speed limits were varied and the results showed that a temporary 30km/h speed restriction gave overestimations of the mean speeds of a trip for all combinations of original and temporary speed limits over all distances. Finally, some psychological issues and applied implications for speed regulation policies were discussed.

  • 12. Vadeby, Anna
    et al.
    Forsman, Asa
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Sandberg, David
    Anund, Anna
    Sleepiness and prediction of driver impairment in simulator studies using a Cox proportional hazard approach2010In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 42, no 3, p. 835-41Article in journal (Refereed)
    Abstract [en]

    Cox proportional hazard models were used to study relationships between the event that a driver is leaving the lane caused by sleepiness and different indicators of sleepiness. In order to elucidate different indicators' performance, five different models developed by Cox proportional hazard on a data set from a simulator study were used. The models consisted of physiological indicators and indicators from driving data both as stand alone and in combination. The different models were compared on two different data sets by means of sensitivity and specificity and the models' ability to predict lane departure was studied. In conclusion, a combination of blink indicators based on the ratio between blink amplitude and peak closing velocity of eyelid (A/PCV) (or blink amplitude and peak opening velocity of eyelid (A/POV)), standard deviation of lateral position and standard deviation of lateral acceleration relative road (ddy) was the most sensitive approach with sensitivity 0.80. This is also supported by the fact that driving data only shows the impairment of driving performance while blink data have a closer relation to sleepiness. Thus, an effective sleepiness warning system may be based on a combination of lane variability measures and variables related to eye movements (particularly slow eye closure) in order to have both high sensitivity (many correct warnings) and acceptable specificity (few false alarms).

  • 13.
    Watling, Christopher N.
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Queensland University of Technology, Australia.
    Armstrong, Kerry A.
    Radun, Igor
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. University of Helsinki, Finland.
    Examining signs of driver sleepiness, usage of sleepiness countermeasures and the associations with sleepy driving behaviours and individual factors2015In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 85, p. 22-29Article in journal (Refereed)
    Abstract [en]

    The impairing effect from sleepiness is a major contributor to road crashes. The ability of a sleepy driver to perceive their level of sleepiness is an important consideration for road safety as well as the type of sleepiness countermeasure used by drivers as some sleepiness countermeasures are more effective than others. The aims of the current study were to determine the extent that the signs of driver sleepiness were associated with sleepy driving behaviours, as well as determining which individual factors (demographic, work, driving, and sleep-related factors) were associated with using a roadside or in-vehicle sleepiness countermeasure. A sample of 1518 Australian drivers from the Australian State of New South Wales and the neighbouring Australian Capital Territory took part in the study. The participants' experiences with the signs of sleepiness were reasonably extensive. A number of the early signs of sleepiness (e.g., yawning, frequent eye blinks) were related with continuing to drive while sleepy, with the more advanced signs of sleepiness (e.g., difficulty keeping eyes open, dreamlike state of consciousness) associated with having a sleep-related close call. The individual factors associated with using a roadside sleepiness countermeasure included age (being older), education (tertiary level), difficulties getting to sleep, not continuing to drive while sleepy, and having experienced many signs of sleepiness. The results suggest that these participants have a reasonable awareness and experience with the signs of driver sleepiness. Factors related to previous experiences with sleepiness were associated with implementing a roadside countermeasure. Nonetheless, the high proportions of drivers performing sleepy driving behaviours suggest that concerted efforts are needed with road safety campaigns regarding the dangers of driving while sleepy.

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