| 1. |
- 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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| 2. |
- Anund, Anna, et al.
(författare)
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Observer Rated Sleepiness and Real Road Driving : An Explorative Study
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5, s. e64782-
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to explore if observer rated sleepiness (ORS) is a feasible method for quantification of driver sleepiness in field studies. Two measures of ORS were used:one for behavioural signs based on facial expression, body gestures and body movements labelled B-ORS, andone based on driving performance e.g. if swerving and other indicators of impaired driving occurs, labelled D-ORSA limited number of observers sitting in the back of an experimental vehicle on a motorway about 2 hours repeatedly 3 times per day (before lunch, after lunch, at night) observed 24 participant's sleepiness level with help of the two observer scales. At the same time the participant reported subjective sleepiness (KSS), EOG was recorded (for calculation of blink duration) and several driving measure were taken and synchronized with the reporting.Based on mixed model Anova and correlation analysis the result showed that observer ratings of sleepiness based on drivers' impaired performance and behavioural signs are sensitive to extend the general pattern of time awake, circadian phase and time of driving. The detailed analysis of the subjective sleepiness and ORS showed weak correspondence on an individual level. Only 16% of the changes in KSS were predicted by the observer. The correlation between the observer ratings based on performance (D-ORS) and behavioural signs (B-ORS) are high (r =. 588), and the B-ORS shows a moderately strong association (r =. 360) with blink duration. Both ORS measures show an association (r>0.45) with KSS, whereas the association with driving performance is weak.The results show that the ORS-method detects the expected general variations in sleepy driving in field studies, however, sudden changes in driver sleepiness on a detailed level as 5 minutes is usually not detected; this holds true both when taking into account driving behaviour or driver behavioural signs.
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| 3. |
- Hallvig, David, et al.
(författare)
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Real driving at night - predicting lane departures from physiological and subjective sleepiness
- 2014
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Ingår i: Biological Psychology. - : Elsevier BV. - 0301-0511 .- 1873-6246. ; 101, s. 18-23
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Tidskriftsartikel (refereegranskat)abstract
- Only limited information is available on how driving performance relates to physiological and subjective sleepiness on real roads. This relation was the focus of the present study. 33 volunteers drove for 90min on a rural road during the afternoon and night in an instrumented car, while electroencephalography and electrooculography and lane departures were recorded continuously and subjective ratings of sleepiness were made every 5min (Karolinska Sleepiness Scale - KSS). Data was analyzed using Bayesian multilevel modeling. Unintentional LDs increased during night driving, as did KSS and long blink durations(LBD). Lateral position moved to the left . LDs were predicted by self-reported sleepiness and LBDs across time and were significantly higher in individuals with high sleepiness. Removal of intentional LDs, enhanced the KSS/LD relation. It was concluded that LDs, KSS, and LBDs are strongly increased during night driving and that KSS predicts LDs.
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| 4. |
- Åkerstedt, Torbjörn, et al.
(författare)
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Having to stop driving at night because of dangerous sleepiness : awareness, physiology and behaviour
- 2013
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Ingår i: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 22:4, s. 380-388
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Tidskriftsartikel (refereegranskat)abstract
- A large number of accidents are due to the driver falling asleep at the wheel, but details of this link have not been studied on a real road. The purpose of the present study was to describe the development of sleepiness indicators, leading to the drive being terminated prematurely by the onboard expert driving instructor because of imminent danger. Eighteen individuals participated during a day drive and a night drive on a motorway (both 90 min). Eight drivers terminated (N) prematurely (after 43 min) because of sleep-related imminent danger [according to the driving instructor or their own judgement (two cases)].The results showed very high sleepiness ratings (8.5 units on the Karolinska Sleepiness Scale) immediately before termination (<7 at a similar time interval for those 10 who completed the drive). Group N also showed significantly higher levels of sleep intrusions on the electroencephalography/electro-oculography (EEG/EOG) than those who completed the drive (group C). The sleep intrusions were increased in group N during the first 40 min of the night drive. During the day drive, sleep intrusions were increased significantly in group N. The night drive showed significant increases of all sleepiness indicators compared to the day drive, but also reduced speed and driving to the left in the lane. It was concluded that 44% of drivers during late-night driving became dangerously sleepy, and that this group showed higher perceived sleepiness and more sleep intrusions in the EEG/EOG.
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| 5. |
- Åkerstedt, Torbjörn, et al.
(författare)
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Normative data on the diurnal pattern of the Karolinska Sleepiness Scale ratings and its relation to age, sex, work, stress, sleep quality and sickness absence/illness in a large sample of daytime workers
- 2017
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Ingår i: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 26:5, s. 559-566
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Tidskriftsartikel (refereegranskat)abstract
- Self-rated sleepiness responds to sleep loss, time of day and work schedules. There is, however, a lack of a normative reference showing the diurnal pattern during a normal working day, compared with a day off, as well as differences depending on stress, sleep quality, sex, age and being sick listed. The present study sought to provide such data for the Karolinska Sleepiness Scale. Participants were 431 individuals working in medium-sized public service units. Sleepiness (Karolinska Sleepiness Scale, scale 1-9) was rated at six times a day for a working week and 2 days off (>90.000 ratings). The results show a clear circadian pattern, with high values during the morning (4.5 at 07:00 hours) and evening (6.0 at 22:00 hours), and with low values (3-4) during the 10:0016: 00 hours span. Women had significantly higher (0.5 units) Karolinska Sleepiness Scale values than men, as did younger individuals (0.3 units), those with stress (1.3 units above the low-stress group) and those with poor sleep quality (1.0 units above those with qood sleep quality). Days off showed reduced sleepiness (0.7 units), while being sick listed was associated with an increased sleepiness (0.8 units). Multiple regression analysis of mean sleepiness during the working week yielded mean daytime stress, mean sleep quality, age, and sex as predictors (not sleep duration). Improved sleep quality accounted for the reduced sleepiness during days off, but reduced stress was a second factor. Similar results were obtained in a longitudinal mixed-model regression analysis across the 7 days of the week. The percentage of ratings at Karolinska Sleepiness Scale risk levels (8 + 9) was 6.6%, but most of these were obtained at 22:00 hours. It was concluded that sleepiness ratings are strongly associated with time of day, sleep quality, stress, work day/day off, being ill, age, and sex.
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