| 1. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Effects of the road environment on the development of driver sleepiness in young male drivers
- 2018
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Ingår i: Accident Analysis and Prevention. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0001-4575 .- 1879-2057. ; 112, s. 127-134
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Abtahi, Farhad, et al.
(författare)
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Association of drivers’ sleepiness with heart rate variability : A pilot study with drivers on real roads
- 2018
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Ingår i: IFMBE Proceedings. - Singapore : Springer Verlag. - 9789811051210 ; , s. 149-152
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Konferensbidrag (refereegranskat)abstract
- Vehicle crashes lead to huge economic and social consequences, and one non-negligible cause of accident is driver sleepiness. Driver sleepiness analysis based on the monitoring of vehicle acceleration, steering and deviation from the road or physiological and behavioral monitoring of the driver, e.g., monitoring of yawning, head pose, eye blinks and eye closures, electroencephalogram, electrooculogram, electromyogram and electrocardiogram (ECG), have been used as a part of sleepiness alert systems.Heart rate variability (HRV) is a potential method for monitoring of driver sleepiness. Despite previous positive reports from the use of HRV for sleepiness detection, results are often inconsistent between studies. In this work, we have re-evaluated the feasibility of using HRV for detecting drivers’ sleepiness during real road driving. A database consists of ECG measurements from 10 drivers, driving during morning, afternoon and night sessions on real road were used. Drivers have reported their average sleepiness level by using the Karolinska sleepiness scale once every five minutes. Statistical analysis was performed to evaluate the potential of HRV indexes to distinguish between alert, first signs of sleepiness and severe sleepiness states. The results suggest that individual subjects show different reactions to sleepiness, which produces an individual change in HRV indicators. The results motivate future work for more personalized approaches in sleepiness detection.
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| 3. |
- Ahlström, Christer, et al.
(författare)
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Dangerous use of mobile phones and other communication devices while driving : A toolbox of counter-measures
- 2013
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Ingår i: Proceedings of the 16th International Conference Road Safety on Four Continents. - Linköping : Statens väg- och transportforskningsinstitut.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of mobile phone and similar devices while driving has been a topic of discussion and research for several years. It is now an established fact that driving performance is deteriorated due to distraction but no clear conclusions can yet be drawn concerning influence on crash rates. Better studies on this relationship is needed. Most countries in Europe and many countries elsewhere have introduced different types of bans for handheld devices. Sweden has, however, no such bans. VTI was commissioned by the Swedish Government to outline possible means to reduce the dangerous usage of mobile phones and other communication devices while driving as alternatives to banning. This task was a result of a previous VTI-state-of-the-art review of research on mobile phone and other communication device usage while driving. One of the findings in the review was that bans on handheld phones did not appear to reduce the number of crashes.Eighteen different countermeasures in three main areas were suggested. (1) Technical solutions such as countermeasures directed towards the infrastructure, the vehicle and the communication device. (2) Education and information, describing different ways to increase knowledge and understanding among stakeholders and different driver categories. (3) Different possibilities for how society, industry and organisations can influence the behaviour of individuals, via policies, rules, recommendations and incentives. Our conclusion is that a combination of different countermeasures is needed – where education and information to the drivers are combined with support and incentives for a safe usage of different communication devices.
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| 4. |
- Ahlström, Christer, et al.
(författare)
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Fit-for-duty test for estimation of drivers sleepiness level: Eye movements improve the sleep/wake predictor
- 2013
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Ingår i: Transportation Research Part C. - : Elsevier. - 0968-090X .- 1879-2359. ; 26, s. 20-32
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Tidskriftsartikel (refereegranskat)abstract
- Driver sleepiness contributes to a considerable proportion of road accidents, and a fit-for-duty test able to measure a drivers sleepiness level might improve traffic safety. The aim of this study was to develop a fit-for-duty test based on eye movement measurements and on the sleep/wake predictor model (SWP, which predicts the sleepiness level) and evaluate the ability to predict severe sleepiness during real road driving. Twenty-four drivers participated in an experimental study which took place partly in the laboratory, where the fit-for-duty data were acquired, and partly on the road, where the drivers sleepiness was assessed. A series of four measurements were conducted over a 24-h period during different stages of sleepiness. Two separate analyses were performed; a variance analysis and a feature selection followed by classification analysis. In the first analysis it was found that the SWP and several eye movement features involving anti-saccades, pro-saccades, smooth pursuit, pupillometry and fixation stability varied significantly with different stages of sleep deprivation. In the second analysis, a feature set was determined based on floating forward selection. The correlation coefficient between a linear combination of the acquired features and subjective sleepiness (Karolinska sleepiness scale, KSS) was found to be R = 0.73 and the correct classification rate of drivers who reached high levels of sleepiness (KSS andgt;= 8) in the subsequent driving session was 82.4% (sensitivity = 80.0%, specificity = 84.2% and AUC = 0.86). Future improvements of a fit-for-duty test should focus on how to account for individual differences and situational/contextual factors in the test, and whether it is possible to maintain high sensitive/specificity with a shorter test that can be used in a real-life environment, e.g. on professional drivers.
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| 5. |
- Ahlström, Christer, 1977-, et al.
(författare)
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The effect of daylight versus darkness on driver sleepiness : A driving simulator study
- 2018
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Ingår i: Journal of Sleep Research. - : Wiley-Blackwell Publishing Inc.. - 0962-1105 .- 1365-2869. ; 27:3
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Tidskriftsartikel (refereegranskat)abstract
- Driver sleepiness studies are often carried out with alert drivers during daytime and sleep-deprived drivers during night-time. This design results in a mixture of different factors (e.g. circadian effects, homeostatic effects, light conditions) that may confound the results. The aim of this study was to investigate the effect of light conditions on driver sleepiness. Thirty young male drivers (23.6 ± 1.7 years old) participated in a driving simulator experiment where they drove on a rural road. A 2 × 2 design was used with the conditions daylight versus darkness, and daytime (full sleep) versus night-time (sleep deprived). The results show that light condition had an independent effect on the sleepiness variables. The subjective sleepiness measured by Karolinska Sleepiness Scale was higher, lateral position more left-oriented, speed lower, electroencephalogram alpha and theta higher, and blink durations were longer during darkness. The number of line crossings did not change significantly with light condition. The day/night condition had profound effects on most sleepiness indicators while controlling for light condition. The number of line crossings was higher during night driving, Karolinska Sleepiness Scale was higher, blink durations were longer and speed was lower. There were no significant interactions, indicating that light conditions have an additive effect on sleepiness. In conclusion, Karolinska Sleepiness Scale and blink durations increase primarily with sleep deprivation, but also as an effect of darkness. Line crossings are mainly driven by the need for sleep and the reduced alertness at the circadian nadir. Lane position is, however, more determined by light conditions than by sleepiness.
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| 6. |
- Ahlström, Christer, et al.
(författare)
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Video-based observer rated sleepiness versus self-reported subjective sleepiness in real road driving
- 2015
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Ingår i: European Transport Research Review. - : Springer Science and Business Media LLC. - 1867-0717 .- 1866-8887. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- Observer-rated sleepiness (ORS) based on video recordings of the driver’s face is often used when analysing naturalistic driving data. The aim of this study is to investigate if ORS ratings agree with subjective self-reported sleepiness (SRS).Forty raters assessed 54 video-clips showing drivers with varying levels of sleepiness. The video-clips were recorded during a field experiment focusing on driver sleepiness using the same cameras that are typically used in large-scale field studies. The weak results prompted a second test. Ten human factors researchers made pairwise comparisons of videos showing the same four participants in an alert versus a very sleepy condition. The task was simply to select the video-clip where the driver was sleepy.The overall average percentage of video segments where ORS and SRS matched was 41 % in Test 1. ORS 0 (alert) and ORS 2 (very sleepy) were easier to score than ORS 1 and it was slightly harder to rate night-time drives. Inter-rater agreement was low, with average Pearson’s r correlations of 0.19 and Krippendorff’s alpha of 0.15. In Test 2, the average Pearson’s r correlations was 0.35 and Krippendorff’s alpha was 0.62. The correspondence between ORS and SRS showed an agreement of 35 %.The results indicate that ORS ratings based on real road video recordings correspond poorly with SRS and have low inter-rater agreement. Further research is necessary in order to further evaluate the usefulness of ORS as a measure of sleepiness.
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| 7. |
- Andersson, Jan, et al.
(författare)
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Trafiksäkerhetspåverkan vid omkörning av 30-metersfordon
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Trafikverket överväger att tillåta längre och tyngre fordon på vägarna förutsatt att de inte påverkar trafiksäkerheten negativt. Syftet med studien var att undersöka säkerhetseffekten av fordonslängd, speciellt med avseende på olycksrisken vid omkörningar. Intervjuade förare av en 30-meters timmerbil hade inte upplevt de farhågor som förare av normallånga lastbilar uttryckt i samband med trånga rondeller och korsningar, men de nämner betydelsen av stödjande åkeri, arbetsmiljö och fordonsutrustning. En simulatorstudie studerade bilförares omkörningar av ett 30- och ett 18,75-metersfordon på en 2+1-väg i situationen då två körfält går ihop till ett. Tidluckan till ett återstående körfält var i genomsnitt 0,2 s (sign.) kortare efter omkörningar av 30-metersfordonet i situationer då bakänden var i samma relativa position som för 18,75-metersfordonet vid början av omkörningen. En fältstudie analyserade videoinspelade omkörningar av en 30- och en 24-meters timmerbil på en 2+1-väg och en tvåfältig väg. Ingen signifikant skillnad i tidluckor kunde påvisas mellan omkörningar av de två fordonen för någon av vägtyperna. Det senare resultatet ska dock tolkas med försiktighet på grund av ojämnt distribuerad data som insamlats under specifika förhållanden. Slutsatserna är att det finns en liten tendens till negativ säkerhetseffekt vid omkörningar av längre fordon, och att fler fältstudier är nödvändiga.
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| 8. |
- Anund, Anna, 1964-, et al.
(författare)
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An on-road study of sleepiness in split shifts among city bus drivers
- 2018
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Ingår i: Accident Analysis and Prevention. - : Elsevier. - 0001-4575 .- 1879-2057. ; 114, s. 71-76
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Anund, Anna, 1964-, et al.
(författare)
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Are professional drivers less sleepy than non-professional drivers?
- 2018
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Ingår i: Scandinavian Journal of Work, Environment and Health. - : SCANDINAVIAN JOURNAL WORK ENVIRONMENT & HEALTH. - 0355-3140 .- 1795-990X. ; 44:1, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- Objective It is generally believed that professional drivers can manage quite severe fatigue before routine driving performance is affected. In addition, there are results indicating that professional drivers can adapt to prolonged night shifts and may be able to learn to drive without decreased performance under high levels of sleepiness. However, very little research has been conducted to compare professionals and non-professionals when controlling for time driven and time of day.Method The aim of this study was to use a driving simulator to investigate whether professional drivers are more resistant to sleep deprivation than non-professional drivers. Differences in the development of sleepiness (self-reported, physiological and behavioral) during driving was investigated in 11 young professional and 15 non-professional drivers.Results Professional drivers self-reported significantly lower sleepiness while driving a simulator than nonprofessional drivers. In contradiction, they showed longer blink durations and more line crossings, both of which are indicators of sleepiness. They also drove faster. The reason for the discrepancy in the relation between the different sleepiness indicators for the two groups could be due to more experience to sleepiness among the professional drivers or possibly to the faster speed, which might unconsciously have been used by the professionals to try to counteract sleepiness.Conclusion Professional drivers self-reported significantly lower sleepiness while driving a simulator than non-professional drivers. However, they showed longer blink durations and more line crossings, both of which are indicators of sleepiness, and they drove faster.
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| 10. |
- Anund, Anna, 1964-, et al.
(författare)
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Bussförares arbetstider kopplat till trötthet
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Bussförare i kollektivtrafiken har ofta oregelbundna arbetstider och en arbetssituation som kan innebära hög stress. Dessa faktorer kan leda till allvarlig trötthet. Syftet med denna studie är att belysa hur arbetstiden påverkar sömn, stress, trötthet och körförmåga. Projektet omfattar fyra delstudier: enkätstudie, sömndagböcker och aktigrafi, analys av schemaläggning och ett experiment på riktig väg med bussförare. Hypoteserna var att tidiga morgonturer, delade skift, långa arbetsdagar och få timmars vila mellan arbetspassen bidrar till trötthet, stress och nedsatt körförmåga, som tillsammans kan leda till en sämre säkerhet. De övergripande resultaten stödjer dessa hypoteser. Generellt sett upplevs sömnighet och trötthet under körning som ett problem eftersom förarna anser att detta innebär nedsatt körförmåga, vilket ökar risken för incidenter och olyckor. Totalt 45 procent av förarna hade minst två gånger i månaden svårt att hålla sig vakna när de kör buss och 19 procent hade under det senaste decenniet varit inblandade i en incident där trötthet varit en bidragande orsak. Experimentet med delade skift med tidig start på morgonen stöder dessa rön. Rapporten avslutas med en lista med förslag.
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