| 1. |
- 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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| 2. |
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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, 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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| 5. |
- 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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| 6. |
- Ahlström, Christer, et al.
(författare)
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Measuring driver impairments : Sleepiness, distraction, and workload
- 2012
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Ingår i: IEEE Pulse. - 2154-2287. ; 3:2, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- Snow was falling heavily when Sarah was driving on a slippery road to her cousin’s country cottage. It was dark outside, and the visibility was poor. She had planned to arrive before sunset, but the rental service had made a mistake, and it took hours before she got her rental car at the airport. It was past midnight now, and after a long day of traveling, Sarah was starting to get sleepy.Fortunately, there were only 15 km to go, but her eyelids were starting to feel heavy. To stay awake, she put her favorite CD on, turned up the volume, and started to sing along. This seemed to help a little -good- only 10 km to go. This was when Sarah’s phone started ringing, and she awkwardly tried to find the mute button for the car stereo while answering the phone. As she looked up again, she barely caught a glimpse of the red brake lights of the car in front of her as she smashed into it.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Allvin, Kerstin, 1970, et al.
(författare)
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Elevated serum levels of estradiol, dihydrotestosterone, and inhibin B in adult males born small for gestational age
- 2008
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Ingår i: Journal of Clinical Endocrinology & Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 93:4, s. 1464-9
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Tidskriftsartikel (refereegranskat)abstract
- CONTEXT: Prenatal growth restriction may affect future fertility in both females and males. Studies have shown that growth-retarded male rats have different sexual behavior and disturbed steroidogenesis. OBJECTIVE: We hypothesized that adult human males born small for gestational age (SGA) have an altered sex hormone profile. DESIGN, SETTING, AND PATIENTS: Twenty-five adult males born SGA with median birth weight -2.2 sd scores (SDS) and birth length -2.4 SDS were studied. Median age was 23.1 yr and final height -0.5 SDS. They were compared with 44 male controls with median age 20.5 yr and final height 0.4 SDS. MAIN OUTCOME MEASURE: The primary outcome before the study started was 17beta-estradiol (E(2)) levels in SGA males. RESULTS: The SGA group showed significantly higher median levels of E(2), 17.9 pg/ml (P < 0.001), and dihydrotestosterone (DHT), 0.543 ng/ml (P < 0.05), compared with controls, 12.6 pg/ml and 0.423 ng/ml, respectively. Testosterone (T) levels did not differ between groups. E(2) to T ratio correlated negatively to birth weight (r = -0.40, P < 0.01) and birth length (r = -0.44, P < 0.001). DHT to T ratio correlated negatively to birth weight (r = -0.51, P < 0.001) and birth length (r = -0.38, P < 0.01). Males born SGA also had significantly higher median levels of inhibin B, 164 pg/ml (P < 0.05), compared with controls, 137 pg/ml. Inhibin B correlated negatively to birth length (r = -0.34, P < 0.01). CONCLUSION: SGA males of normal stature have higher levels of E(2), DHT, and inhibin B than controls, indicating a disturbed steroid synthesis or metabolism. Aromatase activity, calculated as E(2) to T ratio, and 5alpha-reductase activity, calculated as DHT to T ratio, is negatively correlated to size at birth.
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| 10. |
- Andersson, Jan, et al.
(författare)
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Traffic safety effects when overtaking 30 meter trucks
- 2012
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Ingår i: Advances in Human Factors and Ergonomics 2012- 14 Volume Set. - : Taylor & Francis. - 146655262X - 9781466552623
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Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to investigate if the introduction of extra-long and heavy trucks has an effect on traffic safety on Swedish roads, especially in relation to overtaking maneuvers. Traffic safety effects will be measured in terms of road user behavior concerning accelerations and time slots. First, focus group interviews with heavy truck drivers. Truck drivers that do not drive extra-long trucks believe that the introduction of extra-long trucks will create a number of traffic safety problems especially in terms of conflicts with ordinary road users. The drivers of extra-long trucks do not experience the problems that ordinary truck drivers predict. The problems they experience can be taken care of with more planning (thinking ahead). They also believe that the traffic sign on the back of the extra-long vehicle has a positive effect. The truck company, working environment and truck equipment are other important aspects mentioned by the drivers of the extra-long vehicles.The simulator study investigates overtaking situations on a 2+1-lane highway, with extra-long trucks (30.4 m) and ordinary trucks (18.75 m). The results reveal that the distance from the rear/front of the truck to the point where only one lane exists affects car drivers’ decision to overtake, independently of truck length. If the truck is in the relatively same position, the timeslot for a safe overtaking maneuver before next one-lane section was reduced significantly for extra-long trucks compared to ordinary trucks. The conclusion is that there exist small tendencies which point in the direction of enhanced traffic safety problems with the introduction of extra-long trucks. The results should, however, be interpreted with caution as the number of data points was few and collected in specific situations and in specific conditions. It was neither considered how the introduction of longer and heavier trucks, given a constant amount of goods, reduces the number of heavy trucks on the road network.
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| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
- 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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| 15. |
- Anund, Anna, 1964-, et al.
(författare)
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Countermeasures for fatigue in transportation : a review of existing methods for drivers on road, rail, sea and in aviation
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim with this study was to gather knowledge about countermeasures for driver fatigue (including sleepiness) in road, rail, sea and air transportation. The knowledge has been used as an input for evaluating advantages and disadvantages with different countermeasures and to estimate their potential to be used regardless mode of transportation. The method used was a literature review and a workshop with experts from all transportation modes. At the workshop the effectiveness of countermeasures for a single mode, but also regardless mode were discussed and a ranking was done. The report discuss the potential of fighting fatigue among drivers for specific mode of transport but also from a more generic point of view, considering scheduling, model prediction of fatigue risk, legislation, a just culture, technical solutions, infrastructure, education, self-administered alertness interventions and fatigue risk management (FRM). The overall judgement was that a just culture, education, possibility to nap and schedules taking the humans limitations into consideration as the most effective countermeasures to fight fatigue, regardless mode of transportation.
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| 16. |
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| 17. |
- Anund, Anna, 1964-, et al.
(författare)
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Deliverable Nr 4 – Consistent treatment in relation to the severity of a curve, a driving simulator study
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this work is to develop guidelines for evaluation of potential treatments, categorized as “self-explaining treatments” by the use of a driving simulator. More specific the driving simulator study had the aim:• To evaluate the effectiveness of curve treatments, in particular to determine whether a combination of treatments on curves according to their severity could help drivers correctly establish the severity of a curve in advance, and therefore adapt their speed appropriately.In total 35 participants, divided into two groups, drove approximately 46 minutes on a rural road with 3 baseline curves without treatment and 9 curves with treatment of varying levels. In total three different treatment levels and three different curves were used. One group received treatments before each curve that correspond to the severity of the curve (slight curve – low treatment level; moderate curve – medium treatment level; severe curve – high treatment level); the other group experienced inconsistent treatments by being exposed to all nine possible combination of curve and treatments.The analysis of the effects on speed in average and at each point (v0 to v5) was done with Mixed Model ANOVA. Dependent variables were speed measurements in the different points along the curve (v0 to v5) and the average speed through the total curve (from point v0 to v5). The analyses were done both for absolute speeds and for the relative change in speed from starting point (v0). Independent variables were consistent/inconsistent group; curve (1-3), treatment level (1–3) and time on task, here called order (1–9). Subject was used as random and nested on group. In addition the most severe curve was analysed separately in order to compare the groups.In conclusion the result showed that in most cases there were significant effects for treatment levels, severity of the curve, order (time on task), and for subject. There was no significant main effect on group (consistent/inconsistent). However, there was an interaction between curve and group, telling us that the consistent marking significantly reduced the average speed among those with consistent treatment. This holds true also for the speed at point v2, v3 and v5. A final argument for the effectiveness of consistent treatment is that if only the severe curve was considered, there was a significant effect of group.Guidelines for evaluationIt was found that our used method to evaluate the effects of speed adjustment worked well. 35 participants each drove approximately 45 minutes. They were divided into a consistent and one inconsistent group. Three levels of treatment and three severities of curves were used. The dependent variable was the speed measured at three points along the curve. This methodology could be used to evaluate other types of self-explaining treatments. But since a driving simulator study requires a lot of planning (expensive) it is suggested to initially do an expert workshop to evaluate and select the suitable SER treatment and also detailed scenario description.
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| 18. |
- Anund, Anna, et al.
(författare)
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Factors associated with self-reported driver sleepiness and incidents in city bus drivers
- 2016
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Ingår i: Industrial Health. - : National Institute of Occupational Safety and Health. - 0019-8366 .- 1880-8026. ; 54:4, s. 337-346
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Tidskriftsartikel (refereegranskat)abstract
- Driver fatigue has received increased attention during recent years and is now considered to be a major contributor to approximately 15-30% of all crashes. However, little is known about fatigue in city bus drivers. It is hypothesized that city bus drivers suffer from sleepiness, which is due to a combination of working conditions, lack of health and reduced sleep quantity and quality.The overall aim with the current study is to investigate if severe driver sleepiness, as indicated by subjective reports of having to fight sleep while driving, is a problem for city based bus drivers in Sweden and if so, to identify the determinants related to working conditions, health and sleep which contribute towards this. The results indicate that driver sleepiness is a problem for city bus drivers, with 19% having to fight to stay awake while driving the bus 2-3 times each week or more and nearly half experiencing this at least 2-4 times per month. In conclusion, severe sleepiness, as indicated by having to fight sleep during driving, was common among the city bus drivers. Severe sleepiness correlated with fatigue related safety risks, such as near crashes.
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| 19. |
- 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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| 20. |
- Anund, Anna, et al.
(författare)
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The effect of low-frequency road noise on driver sleepiness and performance
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this moving base driving simulator study with 19 drivers participating in a random order day and night time, was to evaluate the effect of low-frequency road noise on driver sleepiness and performance, including both long-term and short-term effects.It is a well-known fact today that driver sleepiness is a contributory factor in crashes. Factors considered as sleepiness contributor are mostly related to time of the day, hours being awake and hours slept. Factors contributing to active and passive fatigue are mostly focusing on the level of cognitive load. Less is known what role external factors, e.g. type of road, sound/noise, vibrations etc., have on the ability to stay awake both under conditions of sleepiness and under active or passive fatigue.The results support to some extent the hypothesis that road-induced interior vehicle sound affects driving performance and driver sleepiness. Increased low-frequency noise helps to reduce speed during both day- and night time driving, but also contributes to increase the number of lane crossings during night time.
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| 21. |
- Anund, Anna, 1964-, et al.
(författare)
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The severity of driver fatigue in terms of line crossing : a pilot study comparing day- and night time driving in simulator
- 2017
-
Ingår i: European Transport Research Review. - : Springer Verlag. - 1867-0717 .- 1866-8887. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The overall aim of this study is to compare day-time driving with night-time driving looking at line crossings during self-reported sleepiness and long blinks. The hypothesis is that high levels of self-reported sleepiness (KSS 9) and long blink duration (>0.15 s) will be less associated with critical events during the day-time compared to night-time.Method: The study is based on data from a driving simulator experiment with 16 participants driving 150 km on a typical Swedish motorway scenario twice: once during daytime and once during night time. In total data from 6 segments of 4 km each equally distributed along the drive was averaged and included in the analysis. A Mixed Model Anova was used to test the effects on KSS, Blink Duration and Line Crossings with factors for Session (Day/Night) and Road segment (1–6), and participant as random. In addition, a logistic regression was used to identify when there is a risk for line crossings. Finally, the proportion of line crossings in relation to high KSS values and long blink durations was tested with Fisher’s exact test.Results: The results show no differences in the percentage of Line Crossings to the left during high levels of Karolinska Sleepiness Scale during daytime (33%) compare to night-time (40%). However, there was a significant difference between day and night time line crossings while the driver had long duration blinks (4% during daytime and 35% during night-time). Despite these results the most promising predictor of line crossings in each segment of 4 km/h was KSS with an Odds Ratio of 5.4 with a reference value at Karolinska Sleepiness Scale level 5.Conclusion: In conclusion, the results do not support the hypothesis that high levels of KSS will result in more frequent line crossings at night time compared to day time. However, the result supports the hypothesis that long blink durations are associated with more line crossings when they appear during night time than during daytime. © 2017, The Author(s).
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| 22. |
- Anund, Anna, 1964-, et al.
(författare)
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Utvärderingsmodell för ITS-baserade system vid hållplats : kunskapsöversikt och förslag på forskningsbehov
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Det finns nya produkter av typen varningssystem som syftar till att öka säkerhet och trygghet för oskyddade trafikanter. De har ofta tagits fram med särskilt fokus på barn. Produktutvecklarna har utvärderat sina produkter med positiva resultat och intresset hos Trafikverket och kommuner är stort för flera av dessa produkter. En typ av system är utmärkning vid hållplatser där blinkande ljus aktiveras när det finns oskyddade trafikanter i närheten, ett så kallat ITS-baserat varningssystem. Det finns idag ett antal platser i landet där sådana anläggningar är i bruk som ”försök” och det har skett utvärderingar av valda system vid hållplats som visat att systemen sannolikt är effektiva när det gäller att reducera hastigheten hos förbipasserande. Det finns dock en avsaknad av ett samlat utvärderingsupplägg. Avsaknaden av systematisk utvärdering har bidragit till bristen på formella beslut för att integrera denna typ av produkt i Vägar och Gators Utformning, VGU eller i Trafiklagstiftningen. I Trafikverkets region Stockholm har man utifrån resenärernas behov och i samarbete med kommunerna kring glesbygdsproblematik, särskilt intresse i att dessa produkter blir möjliga att använda. En förutsättning för detta är en systematisk utvärdering med avseende på om ett specifikt system fyller den funktion som det var avsett att fylla.
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| 23. |
- Filtness, Ashleigh J, et al.
(författare)
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Sleep-related eye symptoms and their potential for identifying driver sleepiness
- 2014
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Ingår i: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 23:5, s. 568-75
-
Tidskriftsartikel (refereegranskat)abstract
- The majority of individuals appear to have insight into their own sleepiness, but there is some evidence that this does not hold true for all, for example treated patients with obstructive sleep apnea. Identification of sleep-related symptoms may help drivers determine their sleepiness, eye symptoms in particular show promise. Sixteen participants completed four motorway drives on two separate occasions. Drives were completed during daytime and night-time in both a driving simulator and on the real road.Ten eye symptoms were rated at the end of each drive, and compared with driving performance and subjective and objective sleep metrics recorded during driving. 'Eye strain', 'difficulty focusing', 'heavy eyelids' and 'difficulty keeping the eyes open' were identified as the four key sleep-related eye symptoms. Drives resulting in these eye symptoms were more likely to have high subjective sleepiness and more line crossings than drives where similar eye discomfort was not reported. Furthermore, drivers having unintentional line crossings were likely to have 'heavy eyelids' and 'difficulty keeping the eyes open'. Results suggest that drivers struggling to identify sleepiness could be assisted with the advice 'stop driving if you feel sleepy and/or have heavy eyelids or difficulty keeping your eyes open'.
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| 24. |
- Fors, Carina, et al.
(författare)
-
A comparison of driver sleepiness in the simulator and on the real road
- 2018
-
Ingår i: Journal of Transportation Safety and Security. - : Taylor & Francis. - 1943-9962 .- 1943-9970. ; 10:1-2, s. 72-87
-
Tidskriftsartikel (refereegranskat)abstract
- For safety reasons as well as for experimental control, driver sleepiness experiments are often run in simulators. The aim of this study is to compare the development of driver sleepiness in an advanced driving simulator experiment with real road driving. Sixteen drivers participated in the experiment, which included daytime and night-time driving on a real motorway and in an advanced driving simulator.The results showed that there were significantly higher levels of Karolinska Sleepiness Scale (KSS) ratings, longer blink durations, lower percentage of gazes directed toward the road center (PRC), and higher speed, in the simulator compared to the real road. The pattern of change with task progression was consistent between simulator driving and real road driving for all investigated variables, that is, speed, KSS, line crossings, blink duration, and PRC. However, the relative differences were higher during daytime compared to night-time driving.Results from a questionnaire showed that it was more boring and more demanding to stay alert in the simulator. In conclusion, the development of sleepiness over time is similar in the simulator as compared to the real road, though the absolute sleepiness level is higher in the simulator.
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| 25. |
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| 26. |
- Fors, Carina, et al.
(författare)
-
Accelerated testing of FCW for trucks : part 2: driving behaviour after exposure to repeated critical events
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Forward collision warning (FCW) systems alert the driver of an imminent rear-end collision with the vehicle ahead. FCW systems are difficult to test and evaluate in a real driving situation and a simulator study can thus be a feasible way of assessing various aspects of FCW systems, such as effectiveness and acceptance. A driving simulator allows for repeated exposure to critical situations, however, there is a risk that repeated critical situations reduce the realism and result in a change in driving behaviour. The aim of this study was to assess driving behaviour during non-critical parts of a driving session that contained repeated critical situations. In a truck simulator 48 professional drivers participated in two driving sessions. The first session aimed at evaluating a FCW system which is reported elsewhere (classified). The second session was a 35 min long motorway drive with two critical and three less critical events. Between all events there was a car following situation. 32 of the drivers had a FCW system while the remaining 16 drivers had no FCW. Mean speed between the events, minimum distance to the vehicle in front in the car following situation, and performance on a secondary task - the arrows task - were used as measures of driving behaviour. In addition, the drivers answered a questionnaire about their driving behaviour.
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| 27. |
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| 28. |
- Fors, Carina, et al.
(författare)
-
Analysis of breathing-related variations in ECG-triggered laser Doppler perfusion signals measured on the beating heart during surgery
- 2006
-
Ingår i: Computers in cardiology. - 0276-6574. ; 33, s. 181-184
-
Tidskriftsartikel (refereegranskat)abstract
- Laser Doppler perfusion monitoring (LDPM) is amethod to assess microvascular perfusion. A modified,ECG-triggered LDPM system has been developed tomeasure myocardial perfusion with minimum influencefrom heart motion. With this method, one systolic (PLS)and one diastolic (PLD) perfusion value is obtained.The aim of this study was to analyse breathing-relatedvariations in PLS and PLD measured during open-heartsurgery. The phase delays between PLS, PLD, meanarterial blood pressure (MAP), heart rate and, indirectly,the respiration were determined.MAP tended to be in phase with or precede thevariations in PLD, i.e., PLD was at a maximum at the endof inspiration or at the beginning of expiration. No clearrelation between PLS and any of the other signals couldbe found.
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| 29. |
- Fors, Carina, et al.
(författare)
-
Camera-based sleepiness detection : final report of the project SleepEYE
- 2011
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Two literature reviews were conducted in order to identify indicators of driver sleepiness and distraction. Three sleepiness indicators – blink duration, blink frequency and Perclos – were implemented in the camera system.The aims of the study were firstly to develop and evaluate a low cost 1-camera unit for detection of driver impairment, and secondly to identify indicators of driver sleepiness and to create a sleepiness classifier for driving simulators.The project included two experiments. The first was a field test where 18 participants conducted one alert and one sleepy driving session on a motorway. 16 of the 18 participants also participated in the second experiment which was a simulator study similar to the field test.The field test data was used for evaluation of the 1-camera system, with respect to the sleepiness indicators. Blink parameters from the 1-camera system was compared to blink parameters obtained from a reference 3-camera system and from the EOG. It was found that the 1-camera system missed many blinks and that the blink duration was not in agreement with the blink duration obtained from the EOG and from the reference 3-camera system. However, the results also indicated that it should be possible to improve the blink detection algorithm since the raw data looked well in many cases where the algorithm failed to identify blinks.The sleepiness classifier was created using data from the simulator experiment. In the first step, the indicators identified in the literature review were implemented and evaluated. The indicators also included driving and context related parameters in addition to the blink related ones. The most promising indicators were then used as inputs to the classifier.
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| 30. |
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| 31. |
- Fors, Carina, 1978-
(författare)
-
Evaluation of a Laser Doppler System for Myocardial Perfusion Monitoring
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Coronary artery bypass graft (CABG) surgery is a common treatment for patients with coronary artery disease. A potential complication of CABG is myocardial ischemia or infarction. In this thesis, a method - based on laser Doppler flowmetry (LDF) - for detection of intra- and postoperative ischemia by myocardial perfusion monitoring is evaluated.LDF is sensitive to motion artifacts. In previous studies, a method for reduction of motion artifacts when measuring on the beating heart has been developed. By using the ECG as a reference, the perfusion signal is measured in intervals during the cardiac cycle where the cardiac motion is at a minimum, thus minimizing the artifacts in the perfusion signal.The aim of this thesis was to investigate the possibilities to use the ECG-triggered laser Doppler system for continuous monitoring of myocardial perfusion in humans during and after CABG surgery. Two studies were performed. In the first study, changes in myocardial perfusion during CABG surgery were investigated (n = 13), while the second study focused on postoperative measurements (n = 13). In addition, an ECG-triggering method was implemented and evaluated.It was found that the large variations in myocardial perfusion during CABG surgery could be monitored with the ECG-triggered laser Doppler system. Furthermore, a perfusion signal of good quality could be registered postoperatively from the closed chest in ten out of thirteen patients. In eight out of ten patients, a proper signal was obtained also the following morning, i.e., about 20 hours after probe insertion. The results show that respiration and blood pressure can have an influence on the perfusion signal.In conclusion, the results indicate that the method is able to detect fluctuations in myocardial perfusion under favourable circumstances. However, high heart rate, abnormal cardiac motion, improper probe attachment and limitations in the ECG-triggering method may result in variations in the perfusion signal that are not related to tissue perfusion.
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| 32. |
- Fors, Carina, 1978-, et al.
(författare)
-
Heldragen kantlinje på tvåfältsväg : hastighet och synbarhet
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med studien var att undersöka hur heldragen respektive intermittent kantlinje påverkar reshastigheten på tvåfältsväg, samt att undersöka om det finns en skillnad i hållbarhet för de två linjetyperna. Studien genomfördes på en 4 km lång landsvägssträcka under en treårsperiod. Första året hade hela sträckan heldragen kantlinje. Under andra och tredje året hade halva sträckan heldragen kantlinje, medan den andra halvan hade intermittent kantlinje. Mätningar av reshastighet för fria (ostörda) personbilar gjordes varje år studien pågick, både i dagsljus och i mörker, i torrt väglag. Under andra och tredje året gjordes även mätningar av kantlinjernas funktion, i form av retroreflexion och luminanskoefficient. Resultaten visade att kantlinjens utformning inte påverkade reshastigheten, varken i dagsljus eller i mörker. Pre-view-time, det vill säga synbarhetsavståndet uttryckt i sekunder givet observatörens hastighet, var signifikant högre för heldragen än för intermittent kantlinje. Under de två år mätningar gjordes av kantlinjernas funktion kunde ingen skillnad i hållbarhet påvisas mellan de två linjetyperna. Utifrån ett trafiksäkerhets- och komfortperspektiv talar resultaten för användning av heldragen kantlinje på tvåfältsväg, åtminstone på kurviga och kuperade vägar.
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| 33. |
- Fors, Carina, et al.
(författare)
-
Interface design of eco-driving support systems : Truck drivers’ preferences and behavioural compliance
- 2015
-
Ingår i: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 58, s. 706-720
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to investigate the perceived usefulness of various types of in-vehicle feedback and advice on fuel efficient driving. Twenty-four professional truck drivers participated in a driving simulator study. Two eco-driving support systems were included in the experiment: one that provided continuous information and one that provided intermittent information. After the simulator session, the participants were interviewed about their experiences of the various constituents of the systems. In general, the participants had a positive attitude towards eco-driving support systems and behavioural data indicated that they tended to comply with the advice given. However, different drivers had very different preferences with respect to what type of information they found useful. The majority of the participants preferred simple and clear information. The eco-driving constituents that were rated as most useful were advice on gas pedal pressure, speed guidance, feedback on manoeuvres, fuel consumption information and simple statistics. It is concluded that customisable user interfaces are recommended for eco-driving support systems for trucks.
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| 34. |
- Fors, Carina, 1978-, et al.
(författare)
-
Intermittenta, heldragna och profilerade vägmarkeringars funktion över tid
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Belagda vägar förses vanligtvis med längsgående vägmarkeringar, vilka kan utformas på olika sätt. Tvåfältsvägar ska i normalfallet ha en 10 eller 15 cm bred intermittent kantlinje, men heldragen kantlinje kan användas till exempel då man vill öka synbarheten. Om vägens årsdygnsmedeltrafik (ÅDT) ≥ 2000 ska kantlinjerna dessutom vara våtsynbara, vilket oftast åstadkoms genom att göra markeringen profilerad.Syftet med projektet var att undersöka om det finns någon skillnad i hållbarhet mellan intermittent och heldragen kantlinje, samt att undersöka om det finns någon skillnad i funktion och hållbarhet hos olika typer av profilerade markeringar. I det första delprojektet applicerades intermittenta respektive heldragna kantlinjer på en tvåfältsväg, vilka sedan följdes upp med årliga mätningar av retroreflexion RL och luminanskoefficient Qd under fyra år. I det andra delprojektet lades ett provfält med sex olika typer av markeringar: plan, rillad, kamflex, longflex, trappflex och plan+trappflex.Uppföljande mätningar av retroreflexion RL på både torra och våta markeringar samt luminanskoefficient Qd på torra markeringar gjordes efter ett och två år. Ingen skillnad i hållbarhet mellan intermittent och heldragen kantlinje kunde påvisas under de fyra år studien pågick. Gällande profilerade markeringar hade den rillade markeringen bäst funktion, med avseende på alla tre funktionsparametrar. Profilerade markeringar med ett trappmönster (trappflex, plan+trappflex) hade bättre funktion än markeringar med transversella linjer (longflex, kamflex).
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| 35. |
- Fors, Carina, et al.
(författare)
-
Investigation of driver sleepiness in FOT data : final report of the project SleepEYE II, part 2
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Driver sleepiness contributes to a great number of motor vehicle accidents every year. In order to reduce the number of sleepiness related accidents, more knowledge on e.g. prevalence, countermeasures and driver behaviour is needed. Data from field operational tests (FOT) has a potential to provide such knowledge with high ecological validity. The objective of the project was to propose and evaluate methods for identification of driver sleepiness in FOT data. More specifically, the aim was to identify objective indicators of sleepiness – based on driving behaviour, eye blink behaviour and models of circadian rhythm – and to evaluate a subjective video scoring method for estimating driver sleepiness levels. Data from two separate projects were used: 1) the ViP-project SleepEYE, in which a controlled field test was conducted, and 2) euroFOT, which was a large scale FOT. In a first step the data quality of blink-based indicators obtained from a camera system was evaluated. It was concluded that the data quality had to be improved and thus, a new detection algorithm was devised and implemented. The new detection algorithm had an acceptable detection rate (approximately 50 %) when applied to data from the SleepEYE field test, but for euroFOT data the number of identified blinks was very low (< 5 blinks/min) in about half of the trips. There is thus a need for further improvements of the blink detection algorithm. An in-depth study on indicators of driver sleepiness was carried out using data collected in the SleepEYE experiment, with the purpose of employing the best indicators to study driver sleepiness in the euroFOT database. The most promising indicators were found to be mean blink duration and number of line crossings. A sleepiness classifier was suggested based on the distribution of the data (i.e. visual inspection). When applied to SleepEYE data the classifier was found to have good specificity while the sensitivity of the classifier was not so good. From euroFOT no true data on the drivers’ sleepiness levels were available and it was therefore not possible to evaluate the performance of the classifier. However, an explorative analysis showed that only very few data points were classified as sleepy. This may be reasonable since most trips were conducted during daytime, but it is a somewhat disappointing result for the project. A study was carried out on whether it is possible to use video recordings of drivers in order to estimate the drivers’ self-rated level of sleepiness. Forty participants rated 54 one-minute video clips of an equal number of sleepy and alert drivers on a scale with three levels (alert, first signs of sleepiness, very sleepy). The results of the study showed that performing such observer rated sleepiness (ORS) estimations on drivers is extremely difficult. The videos available in FOTs are usually of rather poor quality which, clearly limits the possibility of making reliable observer rated sleepiness estimations. In conclusion, studying driver sleepiness in (existing) FOT data is difficult, for several reasons: 1) eye camera based indicators suffer from detection errors and low detection rate, 2) driving-based indicators are influenced by e.g. road curvature and traffic density, 3) models of sleepiness cannot be used since no information on hours slept and time awake is available, and 4) video scoring is not reliable, at least not given the quality of the available video recordings. In future studies on driver sleepiness in FOTs sleepiness should be addressed in the FOT design. Some information about the drivers' sleep and sleepiness (ratings, sleep diaries, etc.) must be collected during the test; otherwise it will be very difficult to get any useful results.
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| 36. |
- Fors, Carina, 1978-, et al.
(författare)
-
Metoder för att bedöma synavstånd för vägmarkeringar
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Studien syftade till att ta fram en metod för att bedöma längsgående vägmarkeringars synavstånd i fordonsbelysning. Metoden ska användas i en kommande studie för att validera en beräkningsmodell, benämnd Visibility, som nyligen har reviderats. Med modellen beräknas vägmarkeringars synavstånd utifrån olika parametrar, bland annat retroreflexion och area.Studien omfattade en litteraturgenomgång och en serie metodtester i fält. Utifrån litteraturgenomgången och ett fåtal små inledande fälttester togs en kravspecifikation fram. Två metoder, benämnda reflektormetoden respektive kantstolpsmetoden, bedömdes kunna uppfylla kravspecifikationen och de fortsatta testerna inriktades därför på dessa metoder. Reflektormetoden går ut på att vägbanereflektorer placeras intill vägmarkeringen med ett visst avstånd. Bedömningen av synavstånd görs stillastående, genom att ange hur långt vägmarkeringen syns, uttryckt i antal reflektorer. Med kantstolpsmetoden används istället kantstolparnas reflektorer som referenspunkter och vägmarkeringens synavstånd anges därmed i antal kantstolpsreflektorer. Bedömningen görs i fart och observatören bedömer vägmarkeringens synavstånd kontinuerligt över en längre sträcka. Båda metoderna fungerade bra rent praktiskt och upplevdes ge rimliga resultat när de testades var för sig. En jämförelse av metoderna visade dock att de gav väsentligt olika resultat. Orsaken till detta har inte helt klarlagts. Vid ytterligare tester, på väg med intermittenta kantmarkeringar, bedömdes synavstånden genom att räkna antalet synliga markeringar med hjälp av kikare. Denna metod antas ge det mest ”sanna” värdet och den indikerade att kantstolpsmetoden tenderar att överskatta synavstånden, medan reflektormetoden tenderar att underskatta synavstånden något om reflektorerna är placerade nära vägmarkeringen. Att göra bedömningen i stillastående jämfört med i fart hade inte någon väsentlig inverkan på resultatet (synavstånden blev något kortare i fart), men det upplevdes vara svårare att göra en noggrann bedömning i fart.
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| 37. |
- Fors, Carina, 1978-, et al.
(författare)
-
Mobil mätning av vägbelysning
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- För de flesta typer av vägutrustningar finns regelverk som ställer funktionskrav. Exempelvis ska en vägmarkering ha en lägsta retroreflexion för att den ska ha tillräcklig synbarhet. Beträffande vägbelysning finns i Trafikverkets Krav för Vägar och Gators Utformning (VGU) flera olika funktionskrav, bland annat krav på tillåten bländning, krav på avskärmning, belysningsstyrka och den vägyteluminans som belysningen ger. På de allra flesta gator och vägar är luminanskravet den viktigaste parametern, inte minst för att detta har betydelse för möjligheten att upptäckta fotgängare. För att ett krav i regelverket ska vara meningsfullt är det viktigt att det är möjligt att kontrollera om kravet är uppfyllt. Emellertid är luminansmätningar komplicerade och känsliga för störningar från omgivande ljuskällor.Syftet med denna studie har varit att utveckla en prototyp till ett instrument som möjliggör snabba mobila mätningar av vägytans luminans utan risk för störningar från annan trafik.Genomförda tester med instrumentet har visat att mätning av vägyteluminans på längre vägsträckor kan utföras, utan ljusstörningar från annan trafik. Mätningarna är dessutom förhållandevis snabba och kräver ett minimum av manuell databearbetning. Att mätsystemet dessutom har god noggrannhet gör att det lämpar sig för tillståndsmätningar av vägbelysning.
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| 38. |
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| 39. |
- Fors, Carina, et al.
(författare)
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Mätning av friktion på vägmarkering : jämförelse av olika metoder samt utveckling av modell för mobil mätning
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- För vägmarkering finns funktionskrav gällande bland annat markeringens friktion, vilken anges i enheter som avser friktion uppmätt med handhållna instrument. Sådana instrument lämpar sig emellertid inte för mätning av friktion över längre sträckor, eftersom det skulle vara alltför tidskrävande och kostsamt. För att på ett effektivt sätt kunna övervaka ett större vägnät och kontrollera att funktionskraven uppfylls behövs mobila mätmetoder, det vill säga metoder som baseras på instrument monterade på fordon och som möjliggör mätning i trafikhastighet. Vidare är friktionen som uppstår mellan fordon och vägyta hastighetsberoende. Den friktion som kan mätas med handhållna instrument avser friktion i lägre hastigheter, medan det ur trafiksäkerhetssynpunkt snarare är friktion i högre hastigheter som är mest relevant.Föreliggande rapport beskriver resultaten från två studier som handlar om metoder för att mäta eller uppskatta vägmarkeringars friktion mobilt. I den första studien har tre olika mobila metoder, Road Friction Tester (RFT), Traction Watcher One (TWO) och Road Marking Tester (RMT), jämförts med den handhållna metoden Portable Friction Tester (PFT). I den andra studien har en skattningsmodell för friktion i högre hastigheter, baserad på mätningar av vägmarkeringens retroreflexion och textur, tagits fram.Den första studien visade att de olika metoderna ger olika resultat, vilket kan förväntas eftersom storheten friktionstal inte har någon entydig definition utan delvis beror på mätinstrumentets egenskaper. Vid mätning i lägre hastigheter fanns det mellan PFT och RFT respektive TWO förhållandevis tydliga samband (signifikant, korrelationskoefficient r: 0,86–0,89), medan sambandet mellan PFT och RMT var något svagare (signifikant, korrelationskoefficient r: 0,65–0,71). Vid mätning i högre hastigheter var sambandet mellan RFT och TWO relativt tydligt (signifikant, korrelationskoefficient r: 0,80), medan sambanden mellan RMT och RFT respektive TWO var ganska svaga (signifikant, korrelationskoefficient r: 0,31–0,61). Ett genomgående resultat var att TWO gav lägre friktionsvärden än övriga metoder. Det kunde också konstateras att mäthastigheten hos RFT och TWO hade en viss inverkan på den uppmätta friktionen.I den andra studien användes TWO som referensmetod för att ta fram en skattningsmodell för friktion i högre hastigheter. Resultaten visade att friktionen till viss del kan prediceras från materialets retroreflexion och textur, men att sambanden inte är tillräckligt starka för att en modell som baseras på (enbart) dessa två parametrar ska vara användbar i praktiken. En begränsning hos studien är att det inte finns någon standardiserad metod för friktionsmätning på vägmarkering i högre hastigheter. Referensmetoden som användes, TWO, är egentligen avsedd för mätning på vägytor och inte vägmarkering, vilket innebär en osäkerhet i instrumentets förmåga att mäta vägmarkeringars friktion, som kan ha påverkat möjligheterna att ta fram en bra skattningsmodell.
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| 40. |
- Fors, Carina, et al.
(författare)
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Night-time traffic in urban areas : a literature review on road user aspects
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this literature study is to review recent research on night-time traffic from a road user perspective. The report discusses road users' behaviour, needs and problems in relation to other road users as well as to traffic environment. The study includes 128 references from 1998-2008 and it mainly concerns urban areas. The report begins with a chapter about accident statistics, followed by a theoretical background that includes lighting terminology, Swedish regulations on road equipment, and the human eye and night vision. The main part of the report has its focus on five road user groups - drivers, pedestrians, bicyclists, older people and visually impaired people - and their needs, difficulties, performances and behaviour in night-time traffic. The literature gives relatively much information about drivers' situation in night-time traffic, but there is a lack of knowledge in some areas such as drivers' interaction with parts of the driving environment. Also, there is partly a lack of knowledge on pedestrians and older road users. Regarding bicyclists and visually impaired people, there is only very limited literature available.
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| 41. |
- Fors, Carina, 1978-, et al.
(författare)
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Nordic certification system for road marking materials : Version 7:2020
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A Nordic certification system for road marking materials was introduced in 2015. The system is based on documented performance measurements of material samples applied on test fields on public roads. The certification system includes both flat (type I) and structured/profiled (type II) markings, antiskid materials (materials with enhanced friction), temporary markings (Denmark only), inlaid markings (Norway only), materials for hand application and materials with enhanced durability for illuminated high-traffic urban areas.Material tests are carried out at two test sites: one in Norway and one in Denmark. The tests fields are situated on public roads and the tested materials are thus exposed to real traffic conditions and to weather conditions representative for the Nordic countries. The materials are followed up by performance measurements during one or two years. The certification includes requirements on coefficient of retroreflected luminance RL under dry and wet conditions, luminance coefficient under diffuse illumination Qd, friction and colour coordinates. The number of wheel passages is measured at the test sites annually. The certification system includes material identification, which allows for future material sampling and analysis.The report describes the certification system and how it is applied in the Nordic countries. Procedures and methods that are used for application of materials and performance measurements are specified.
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| 42. |
- Fors, Carina, 1978-, et al.
(författare)
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Nordic certification system for road marking materials : Version 8:2021
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A Nordic certification system for road marking materials was introduced in 2015. The system is based on documented performance measurements of material samples applied on test fields on public roads. The certification system includes both flat (type I) and structured/profiled (type II) markings, antiskid materials (materials with enhanced friction), temporary markings, inlaid markings (Norway only), materials for hand application and materials with enhanced durability for illuminated high-traffic urban areas. Material tests are carried out at two test sites: one in Norway and one in Denmark. The test fields are situated on public roads and the tested materials are thus exposed to real traffic conditions and to weather conditions representative for the Nordic countries. The materials are followed up by performance measurements for one or two years. The certification includes requirements on coefficient of retroreflected luminance RL under dry and wet conditions, luminance coefficient under diffuse illumination Qd, friction and chromaticity coordinates. The number of wheel passages is measured at the test sites annually. The certification system includes material identification, which allows for future material sampling and analysis. The certification system is based on the European standards EN 1824 Road marking materials – Road trials, EN 1436 Road marking materials – Road marking performance for road users, EN 12802 Road marking materials – Laboratory methods for identification, and EN 1423 Road marking materials – Drop on materials – Glass beads, antiskid aggregates and mixtures of the two. This document constitutes the guidelines for the Nordic certification system. The document describes the certification procedure, what type of products that are included in the system and the requirements for certification. Furthermore, the procedures and methods used for application of materials, performance measurement and identification analysis are described. The document also gives specifications and practical information regarding the test sites and regarding registration and application of products for certification.
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| 43. |
- Fors, Carina, 1978-, et al.
(författare)
-
Nordic certification system for road marking materials : Version 9:2022
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A Nordic certification system for road marking materials was introduced in 2015. The system is based on documented performance measurements of material samples applied on test fields on public roads. The certification system includes both flat (type I) and structured/profiled (type II) markings, antiskid materials (materials with enhanced friction), temporary markings, inlaid markings (Norway only), materials for hand application and materials with enhanced durability for illuminated high-traffic urban areas. Material tests are carried out at two test sites: one in Norway and one in Denmark. The test fields are situated on public roads and the tested materials are thus exposed to real traffic conditions and to weather conditions representative for the Nordic countries. The materials are followed up by performance measurements for one or two years. The certification includes requirements on coefficient of retroreflected luminance RL under dry and wet conditions, luminance coefficient under diffuse illumination Qd, friction and chromaticity coordinates. The number of wheel passages is measured at the test sites annually. The certification system includes material identification, which allows for future material sampling and analysis. The certification system is based on the European standards EN 1824 Road marking materials – Road trials, EN 1436 Road marking materials – Road marking performance for road users, EN 12802 Road marking materials – Laboratory methods for identification, and EN 1423 Road marking materials – Drop on materials – Glass beads, antiskid aggregates and mixtures of the two. This document constitutes the guidelines for the Nordic certification system. The document describes the certification procedure, what type of products that are included in the system and the requirements for certification. Furthermore, the procedures and methods used for application of materials, performance measurement and identification analysis are described. The document also gives specifications and practical information regarding the test sites and regarding registration and application of products for certification.
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| 44. |
- Fors, Carina, 1978-, et al.
(författare)
-
Nordic certification system for road marking materials : Version 10:2024
- 2024
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A Nordic certification system for road marking materials was introduced in 2015. The system is based on documented performance measurements of material samples applied on test fields on public roads. The certification system includes both flat (type I) and structured/profiled (type II) markings, antiskid materials (materials with enhanced friction), temporary markings, inlaid markings (Norway only), materials for hand application and materials with enhanced durability for illuminated high-traffic urban areas. Material tests are carried out at two test sites: one in Norway and one in Denmark. The test fields are situated on public roads and the tested materials are thus exposed to real traffic conditions and to weather conditions representative for the Nordic countries. The materials are followed up by performance measurements for one or two years. The certification includes requirements on coefficient of retroreflected luminance RL under dry and wet conditions, luminance coefficient under diffuse illumination Qd, friction and chromaticity coordinates. The number of wheel passages is measured at the test sites annually. The certification system includes material identification, to verify that the manufacturer’s declaration of constituents agrees with the material applied on the test field. The certification system is based on the European standards EN 1824 Road marking materials – Road trials, EN 1436 Road marking materials – Road marking performance for road users, EN 12802 Road marking materials – Laboratory methods for identification, and EN 1423 Road marking materials – Drop on materials – Glass beads, antiskid aggregates and mixtures of the two. This document constitutes the guidelines for the Nordic certification system. The document describes the certification procedure, what type of products that are included in the system and the requirements for certification. Furthermore, the procedures and methods used for application of materials, performance measurement and identification analysis are described. The document also gives specifications and practical information regarding the test sites and regarding registration and application of products for certification.
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| 45. |
- Fors, Carina, 1978-, et al.
(författare)
-
Online Laser Doppler Measurements of Myocardial Perfusion
- 2008
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Ingår i: IFMBE Proceedings 22,2008. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783540892076 - 9783540892083 ; , s. 1718-1721
-
Konferensbidrag (refereegranskat)abstract
- Laser Doppler perfusion monitoring is a suitable method for microvascular blood perfusion measurements. When used on a moving tissue or organ, the Doppler signal arising from the moving blood cells may be distorted. ECG triggering of the laser Doppler signal can be used for reducing the influence from movements during measurements on the beating heart. The aim of this study was to determine the most appropriate triggering intervals during the cardiac cycle for online measurements. Recordings from thirteen coronary artery bypass graft (CABG) patients were included in the study. During surgery, the fibre-optic probe was passed through the chest wall and sutured to the left anterior ventricular wall with the probe tip inserted 3–5 mm into the myocardium. After the patient arrived at the intensive care unit a second measurement was initiated and lasted for about two hours. Before the probe was removed a third measurement was performed for about 5 minutes the following morning. A total of 97 data sequences were analysed and the intervals of low and stable perfusion signal were compared to the positions of the T and P peaks in the ECG.It was found that the most appropriate time intervals were in late systole at the T peak [−3, 9] ms and just before the P peak [−28, -10] ms in late diastole. However, the position of these intervals may vary between individuals, because of e.g., abnormal cardiac motion. With the use of the appropriate interval online measurement of the myocardial perfusion on a beating heart appears possible.
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| 46. |
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| 47. |
- Fors, Carina, 1978-, et al.
(författare)
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Revision of criteria for selection of road lighting class : a pre-study
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this project is to investigate the potential in decreasing the energy use of road lighting by a revision of the guidelines regarding the selection of lighting level. The starting point of this work has been the method for selection of lighting classes suggested in the recently published technical report CEN/TR 13201-1, which considers road lighting for drivers and for vulnerable road users. In order to investigate whether CEN/TR 13201-1 is applicable in Sweden, a literature review on guidelines and criteria for selection of road lighting classes was carried out, with the aim of identifying criteria that are scientifically grounded. The literature review was supplemented by a workshop where road lighting criteria were discussed by invited road lighting experts from the Nordic countries. The results from the study show that there is some support that the parameters traffic volume, traffic composition, separation of carriageways, ambient luminosity and navigational task are relevant for the selection of road lighting class, but also that there is a lack of knowledge of road users’ needs and experiences of road lighting. The report gives recommendations for further work on a revision of the guidelines for road lighting, and suggestions for further research studies.
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| 48. |
- Fors, Carina
(författare)
-
Samband mellan synbarhet och vägbelysningens färg : en litteraturstudie om mätmetoder och synbarhetsexperiment
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Befintliga metoder för att mäta och beskriva vägbelysningsparametrar bygger på hur ögat uppfattar ljus idagsljusförhållanden. I mörkertrafik där ljusnivåerna är låga – i det så kallade mesopiska området kan dagens metoder ge missvisande resultat. Mer korrekta mätmetoder kan ge bättre och mer enhetliga ljusförhållanden, men även energibesparingar om belysningsstyrkan för vissa typer av vägbelysning kan sänkas. Den här rapporten sammanfattar litteratur om nya mesopiska mätmetoder och modeller som bättre än dagens metoder predicerar synförmåga i olika typer av vägbelysning/belysningsfärg vid låga ljusnivåer. Vidare granskas och sammanfattas resultat från empiriska studier där man undersökt sambandet mellan synförmåga och belysningens färg. I litteraturen finns flera metoder och modeller föreslagna. Metoderna visar tämligen entydigt att vitt ljus ger bättre synförmåga än gult ljus vid låga (ca 0,1 cd/m2 eller lägre) luminansnivåer men att det är ganska liten skillnad vid högre nivåer (ca 1 cd/m2 eller högre). En begränsning med de föreslagna metoderna är att de är utvecklade i labbmiljö och ännu inte är utvärderade i naturliga trafikmiljöer, bortsett från enstaka studier. Litteraturgenomgången visar att det i dagsläget inte finns tillräckligt vetenskapligt stöd för att göra ändringar i gällande rekommendationer för vägbelysning.
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| 49. |
- Fors, Carina, et al.
(författare)
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Simulator validation with respect to driver sleepiness and subjective experiences : final report of the project SleepEYE II, part 1
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the previous project SleepEYE, which aimed at developing tools for driver sleepiness detection, two experiments were carried out. In the first experiment, 18 drivers conducted two driving sessions on a motorway: one during daytime (alert) and one at night (sleep deprived). Sixteen of the drivers participated in the second experiment, which was similar to the first one, except that the driving sessions were conducted in an advanced moving base driving simulator. In the present study, the validity of the simulator was assessed using data that was collected in the two experiments. The validation analysis had three focuses: 1) general driver and driving behaviour related to driver sleepiness, 2) speed profile at change in posted speed limit, and 3) drivers’ subjective experience of the vehicle, the driving environment and the own driving performance. The results showed that there were significant differences in mean speed, blink duration, percentage road centre (gaze), radius of 95 per cent cone (gaze) and KSS between the simulator and the real road. No such differences were found for left and right line crossings. For all indicators except blink duration, there was no interaction effect between platform (simulator vs. real road) and time on task, which indicates that the signs of sleepiness vary in a similar way regardless of platform. In conclusion, differences between the simulator and the real road with respect to driving and driver behaviour as well as subjective experiences were found, mainly in terms of speed, level of sleepiness and subjective experience of the vehicle. However, the signs of sleepiness and the development of sleepiness over time are similar in the simulator and on the real road, although the level is higher in the simulator. Thus, there is a relative but not absolute validity with respect to driver sleepiness. Similarly, there seems to be a relative validity for speed and changes in speed.
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| 50. |
- Fors, Carina, et al.
(författare)
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Symboler i vägbanan : en sammanställning av gällande regelverk i Danmark, Finland, Norge, Sverige, Nederländerna, Storbritannien och Tyskland
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna studie har syftat till att sammanställa befintliga regelverk och riktlinjer för användandet av symboler i vägbanan i de nordiska länderna Danmark, Finland, Norge och Sverige samt i Nederländerna, Storbritannien och Tyskland. Dessutom har en mindre litteraturstudie genomförts för att undersöka vilka dokumenterade kunskaper regelverken baseras på. Symboler i vägbanan används på liknande sätt i de sju studerade länderna. I stor utsträckning saknas det dock dokumenterade kunskaper och forskning om hur symbolerna ska se ut. Det borde därför finnas utrymme för att standardisera symbolerna inom Norden, vilket skulle kunna ge ett mer enhetligt intryck där trafikanterna känner igen och förstår informationen, samtidigt som utläggningen av symbolerna skulle kunna förenklas. Sammanfattningsvis kan konstateras att, från hastighetssynpunkt, primärt följande symboler skulle kunna vara av intresse att standardisera inom Norden vad gäller användning, utformning och mått:körfältspilarpilar för körfältsbyteväjningspliktstopplikthastighetsbegränsningvägnummer
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