| 1. |
- Anund, Anna, et al.
(författare)
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The effects of driving situation on sleepiness indicators after sleep loss : A driving simulator study
- 2009
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Ingår i: Industrial Health. - : National Institute of Industrial Health. - 0019-8366 .- 1880-8026. ; 47:4, s. 393-401
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Tidskriftsartikel (refereegranskat)abstract
- Almost all studies of sleepy driving are carried out in driving simulators and with monotonous road conditions (no interaction with other cars). The present study investigated indicators of sleepy driving in a more challenging scenario after a night awake. 17 participants drove a high fidelity moving base driving simulator experiment while sleepiness was monitored physiologically and behaviourally. Short periods of situations of free driving (no other vehicles) alternated with short periods of following another vehicle (car following) with and without the possibility to overtake. The result showed that a night of prior sleep loss increased sleepiness levels at the wheel (eye closure duration and lateral variability) compared to after a night of normal sleep. Blink duration while overtaking was significantly lower compared to the other situations, it was at the same level as after night sleep. Speed when passing a stopped school bus was not significantly affected by sleepiness. However the warning caused a more rapid reduction of speed. In conclusion, a moderately challenging driving contest did not affect sleepiness indicators, but a very challenging one did so (overtaking). This suggests that it is important to monitor the driving situation in field operational tests of sleepy driving.
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| 2. |
- Dahlgren, Anna, et al.
(författare)
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Day-to-day variation in saliva cortisol-Relation with sleep, stress and self-rated health.
- 2009
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Ingår i: Biological psychology. - : Elsevier BV. - 1873-6246 .- 0301-0511.
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Tidskriftsartikel (refereegranskat)abstract
- The objective was to examine the day-to-day variation in cortisol among healthy individuals and its relation to the time of saliva sampling, work, stress and fatigue. During 4 consecutive weeks, 14 office workers provided saliva samples (at awakening, 15min after awakening and at bedtime) and made diary ratings for each day. Results showed a variation in cortisol values between participants but also within individuals. After controlling for the individual differences, results showed that low cortisol levels in the morning were associated with sleepiness at awakening and anxiety, exhaustion, and poor health the day before. High evening levels of cortisol were associated with symptoms of stress and poor self-rated health. Further analysis of the cortisol awakening response (CAR) showed that all participants had a mixture of both a positive and negative responses. During mornings with a negative response participants stayed in bed for a longer time after the initial awakening, which might be a sign of snoozing, thus missing the awakening response.
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| 3. |
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| 4. |
- Hallvig, D., et al.
(författare)
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Sleepy driving on the real road and in the simulator - A comparison
- 2013
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575 .- 1879-2057. ; 50, s. 44-50
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Radun, Igor, 1973, et al.
(författare)
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Driver fatigue and the law from the perspective of police officers and prosecutors
- 2013
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Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478 .- 1873-5517. ; 18, s. 159-167
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Tidskriftsartikel (refereegranskat)abstract
- Even though police officers and prosecutors play a key role in traffic law application, little is known about their experiences, attitudes, and opinions regarding the complex issue of driver fatigue and the law. This paper is based on an extensive online survey collected from traffic (N = 129) and local (N = 100) police officers and prosecutors (N = 96) in the context of Finnish traffic law, which forbids driving while fatigued in an article relating to a driver's fitness to drive. While encountering fatigued drivers is very common for police officers, only a small proportion has received training about how to recognize and deal with fatigued drivers. Driving while extremely fatigued is considered rather or extremely negligent behavior by almost all respondents. Although agreement between these three groups exists regarding several issues, they disagree about whether the current law is specific enough, and whether experts might be valuable in court when discussing the possible contribution of fatigue to the cause of a crash. We discuss the application of the law and opinions about the current law formulation, experience and education, as well as general awareness and attitudes, taking into consideration the different nature of police and prosecutor work.
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| 6. |
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| 7. |
- Radun, Igor, et al.
(författare)
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Self-reported circumstances and consequences of driving while sleepy
- 2015
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Ingår i: Transportation Research Part F. - : Elsevier BV. - 1369-8478 .- 1873-5517. ; 32, s. 91-100
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Driver surveys are indispensable sources of information when estimating the role of sleepiness in crash causation. The purpose of the study was to (1) identify the prevalence of driving while sleepy among Finnish drivers, (2) determine the circumstances of such instances, and (3) identify risk factors and risk groups. Survey data were collected from a representative sample of active Finnish drivers (N = 1121). One-fifth of the drivers (19.5%) reported having fallen asleep at the wheel during their driving career, with 15.9% reporting having been close to falling asleep or having difficulty staying awake when driving during the previous twelve months. Epworth Sleepiness Scale scores were found to be associated with both types of sleepiness-related driving instances, while sleep quality was associated only with the latter. Compared to women, men more often reported falling asleep at the wheel; the differences were somewhat smaller with respect to fighting sleep while driving during the previous twelve months. The reported discrepancy in sleepiness-related instances (high prevalence of fighting sleep while driving during the previous twelve months and lower proportion of actually falling asleep) identifies young men (⩜25 years) as one of the main target groups for safety campaigns. Approximately three-quarters of drivers who had fallen asleep while driving reported taking action against falling asleep before it actually happened. Furthermore, almost all drivers who had fallen asleep while driving offered at least one logical reason that could have contributed to their falling asleep. These data indicate some degree of awareness about driving while sleepy and of the potential pre-trip factors that could lead to sleepiness while driving, and supports the notion that falling asleep at the wheel does not come as a (complete) surprise to the driver.
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| 8. |
- Radun, Igor, et al.
(författare)
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Sleepy drivers on a slippery road : A pilot study using a driving simulator
- 2022
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Ingår i: Journal of Sleep Research. - : John Wiley & Sons. - 0962-1105 .- 1365-2869. ; 31:2
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Tidskriftsartikel (refereegranskat)abstract
- Sleepy drivers have problems with keeping the vehicle within the lines, and might often need to apply a sudden or hard corrective steering wheel movement. Such movements, if they occur while driving on a slippery road, might increase the risk of ending off road due to the unforgiving nature of slippery roads. We tested this hypothesis. Twelve young men participated in a driving simulator experiment with two counterbalanced conditions; dry versus slippery road x day (alert) versus night (sleepy) driving. The participants drove 52.5 km on a monotonous two-lane highway and rated their sleepiness seven times using the Karolinska Sleepiness Scale. Blink durations were extracted from an electrooculogram. The standard deviation of lateral position and the smoothness of steering events were measures of driving performance. Each outcome variable was analysed with mixed-effect models with road condition, time-of-day and time-on-task as predictors. The Karolinska Sleepiness Scale increased with time-on-task (p < 0.001) and was higher during night drives (p < 0.001), with a three-way interaction suggesting a small increased sleepiness with driving time at night with slippery road conditions (p = 0.012). Blink durations increased with time-on-task (p < 0.01) with an interaction between time-of-day and road condition (p = 0.040) such that physiological sleepiness was lower for sleep-deprived participants in demanding road conditions. The standard deviation of lateral position increased with time-on-task (p = 0.026); however, during night driving it was lower on a slippery road (p = 0.025). The results indicate that driving in demanding road condition (i.e. slippery road) might further exhaust already sleepy drivers, although this is not clearly reflected in driving performance.
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| 9. |
- Sandberg, David, 1980, et al.
(författare)
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Detecting driver sleeepiness using optimized non-linear combinations of sleepiness indicators
- 2011
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Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 12:1, s. 97-108
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of detecting sleepiness in car drivers. First, a variety of sleepiness indicators (based on driving behavior) proposed in the literature were evaluated. These indicators were then subjected to parametric optimization using stochastic optimization methods. To improve performance, the functional form of some of the indicators was generalized before optimization. Next, using a neural network, the best performing sleepiness indicators were combined with a mathematical model of sleepiness, i.e., the sleep/wake predictor (SWP). The analyses were based on data obtained from a study that involved 12 test subjects at the moving-base driving simulator at the Swedish National Road and Transportation Research Institute (VTI), Linkping, Sweden. The data were derived from 12 1-h driving sessions for each test subject, with varying degrees of sleepiness. The performance measure (range [0,1]) for indicators was taken as the average of sensitivity and specificity. Starting with indicators proposed in the literature, the best such indicator, i.e., the standard deviation of the yaw angle, reached a performance score of 0.72 on previously unseen test data. It was found that indicators based on a given signal gave essentially equal performance after parametric optimization, but in no case was it better than 0.72. The best generalized indicator (the generic variability indicator) obtained a performance score of 0.74. SWP achieved a score of 0.78. However, by nonlinearly combining SWP with the generic variability indicator, a score of 0.83 was obtained. Thus, the results imply that a nonlinear combination of a measure based on driving behavior with a model of sleepiness significantly improves driver sleepiness detection.
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| 10. |
- Sandberg, David, 1980, et al.
(författare)
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The Characteristics of Sleepiness During Real Driving at Night - A Study of Driving Performance, Physiology and Subjective Experience
- 2011
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Ingår i: Sleep. - 1550-9109 .- 0161-8105. ; 34:10, s. 1317-1325
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Tidskriftsartikel (refereegranskat)abstract
- Study Objectives: Most studies of sleepy driving have been carried out in driving simulators. A few studies of real driving are available, but these have used only a few sleepiness indicators. The purpose of the present study was to characterize sleepiness in several indicators during real driving at night, compared with daytime driving. Design: Participants drove 55 km (at 90km/h) on a 9-m-wide rural highway in southern Sweden. Daytime driving started at 09: 00 or 11: 00 (2 groups) and night driving at 01: 00 or 03: 00 (balanced design). Setting: Instrumented car on a real road in normal traffic. Participants: Eighteen participants drawn from the local driving license register. Interventions: Daytime and nighttime drives. Measurement and Results: The vehicle was an instrumented car with video monitoring of the edge of the road and recording of the lateral position and speed. Electroencephalography and electrooculography were recorded, together with ratings of sleepiness every 5 minutes. Pronounced effects of night driving were seen for subjective sleepiness, electroencephalographic indicators of sleepiness, blink duration, and speed. Also, time on task showed significant effects for subjective sleepiness, blink duration, lane position, and speed. Sleepiness was highest toward the end of the nighttime drive. Night driving caused a leftward shift in lateral position and a reduction of speed. The latter two findings, as well as the overall pattern of sleepiness indicators, provide new insights into the effects of night driving. Conclusion: Night driving is associated with high levels of subjective, electrophysiologic, and behavioral sleepiness.
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