| 1. |
- Barua, Shaibal, et al.
(författare)
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Automated EEG Artifact Handling with Application in Driver Monitoring
- 2018
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Ingår i: IEEE journal of biomedical and health informatics. - : IEEE. - 2168-2194 .- 2168-2208. ; 22:5, s. 1350-1361
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Tidskriftsartikel (refereegranskat)abstract
- Automated analyses of electroencephalographic (EEG) signals acquired in naturalistic environments is becoming increasingly important in areas such as brain computer interfaces and behaviour science. However, the recorded EEG in such environments is often heavily contaminated by motion artifacts and eye movements. This poses new requirements on artifact handling. The objective of this paper is to present an automated EEG artifacts handling algorithm which will be used as a pre-processing step in a driver monitoring application. The algorithm, named ARTE (Automated aRTifacts handling in EEG), is based on wavelets, independent component analysis and hierarchical clustering. The algorithm is tested on a dataset obtained from a driver sleepiness study including 30 drivers and 540 30-minute 30-channel EEG recordings. The algorithm is evaluated by a clinical neurophysiologist, by quantitative criteria (signal quality index, mean square error, relative error and mean absolute error), and by demonstrating its usefulness as a pre-processing step in driver monitoring, here exemplified with driver sleepiness classification. All results are compared with a state of the art algorithm called FORCe. The quantitative and expert evaluation results show that the two algorithms are comparable and that both algorithms significantly reduce the impact of artifacts in recorded EEG signals. When artifact handling is used as a pre-processing step in driver sleepiness classification, the classification accuracy increased by 5% when using ARTE and by 2% when using FORCe. The advantage with ARTE is that it is data driven and does not rely on additional reference signals or manually defined thresholds, making it well suited for use in dynamic settings where unforeseen and rare artifacts are commonly encountered.
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| 2. |
- Barua, Shaibal, et al.
(författare)
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Automatic driver sleepiness detection using EEG, EOG and contextual information
- 2019
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Ingår i: Expert systems with applications. - : Elsevier Ltd. - 0957-4174 .- 1873-6793. ; 115, s. 121-135
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Tidskriftsartikel (refereegranskat)abstract
- The many vehicle crashes that are caused by driver sleepiness each year advocates the development of automated driver sleepiness detection (ADSD) systems. This study proposes an automatic sleepiness classification scheme designed using data from 30 drivers who repeatedly drove in a high-fidelity driving simulator, both in alert and in sleep deprived conditions. Driver sleepiness classification was performed using four separate classifiers: k-nearest neighbours, support vector machines, case-based reasoning, and random forest, where physiological signals and contextual information were used as sleepiness indicators. The subjective Karolinska sleepiness scale (KSS) was used as target value. An extensive evaluation on multiclass and binary classifications was carried out using 10-fold cross-validation and leave-one-out validation. With 10-fold cross-validation, the support vector machine showed better performance than the other classifiers (79% accuracy for multiclass and 93% accuracy for binary classification). The effect of individual differences was also investigated, showing a 10% increase in accuracy when data from the individual being evaluated was included in the training dataset. Overall, the support vector machine was found to be the most stable classifier. The effect of adding contextual information to the physiological features improved the classification accuracy by 4% in multiclass classification and by and 5% in binary classification.
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| 3. |
- Nilsson, Emma, et al.
(författare)
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Vehicle Driver Monitoring : sleepiness and cognitive load
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To prevent road crashes, it is important to understand driver related contributing factors. The overall aim of the Vehicle Driver Monitoring project was to advance the understanding of two such factors; sleepiness and cognitive distraction. The project aimed at finding methods to measure the two states, with focus on physiological measures, and to study their effect on driver behaviour. The data collection was done in several laboratory and driving simulator experiments. Much new knowledge and insights were gained in the project. Significant effects of cognitive load as well as of sleepiness were found in several physiological measures. The results also showed that context, including individual and environmental factors, has a great impact on driver behaviours, measures and driver experiences.
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| 4. |
- Ahlström, Christer, 1977-, et al.
(författare)
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A Generalized Method to Extract Visual Time-Sharing Sequences From Naturalistic Driving Data
- 2017
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1524-9050 .- 1558-0016. ; 18:11, s. 2929-2938
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Tidskriftsartikel (refereegranskat)abstract
- Indicators based on visual time-sharing have been used to investigate drivers' visual behaviour during additional task execution. However, visual time-sharing analyses have been restricted to additional tasks with well-defined temporal start and end points and a dedicated visual target area. We introduce a method to automatically extract visual time-sharing sequences directly from eye tracking data. This facilitates investigations of systems, providing continuous information without well-defined start and end points. Furthermore, it becomes possible to investigate time-sharing behavior with other types of glance targets such as the mirrors. Time-sharing sequences are here extracted based on between-glance durations. If glances to a particular target are separated by less than a time-based threshold value, we assume that they belong to the same information intake event. Our results indicate that a 4-s threshold is appropriate. Examples derived from 12 drivers (about 100 hours of eye tracking data), collected in an on-road investigation of an in-vehicle information system, are provided to illustrate sequence-based analyses. This includes the possibility to investigate human-machine interface designs based on the number of glances in the extracted sequences, and to increase the legibility of transition matrices by deriving them from time-sharing sequences instead of single glances. More object-oriented glance behavior analyses, based on additional sensor and information fusion, are identified as the next future step. This would enable automated extraction of time-sharing sequences not only for targets fixed in the vehicle's coordinate system, but also for environmental and traffic targets that move independently of the driver's vehicle.
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| 5. |
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| 6. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Alcohol impairs driver attention and prevents compensatory strategies
- 2023
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Ingår i: Accident Analysis and Prevention. - : Elsevier. - 0001-4575 .- 1879-2057. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- While the negative effects of alcohol on driving performance are undisputed, it is unclear how driver attention, eye movements and visual information sampling are affected by alcohol consumption. A simulator study with 35 participants was conducted to investigate whether and how a driver's level of attention is related to self-paced non-driving related task (NDRT)-engagement and tactical aspects of undesirable driver behaviour under increasing levels of breath alcohol concentration (BrAC) up to 1.0 ‰. Increasing BrAC levels lead to more frequent speeding, short time headways and weaving, and higher NDRT engagement. Instantaneous distraction events become more frequent, with more and longer glances to the NDRT, and a general decline in visual attention to the forward roadway. With alcohol, the compensatory behaviour that is typically seen when drivers engage in NDRTs did not appear. These findings support the theory that alcohol reduces the ability to shift attention between multiple tasks. To conclude, the independent reduction in safety margins in combination with impaired attention and an increased willingness to engage in NDRTs is likely the reason behind increased crash risk when driving under the influence of alcohol. © 2023
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| 7. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Assessment of Suspected Aortic Stenosis by Auto Mutual Information Analysis of Murmurs
- 2007
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Ingår i: Engineering in Medicine and Biology Society, 2007. EMBS 2007. - 9781424407873 ; , s. 1945-1948
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Konferensbidrag (refereegranskat)abstract
- Mild sclerotic thickening of the aortic valve affects 25% of the population, and the condition causes aortic valve stenosis (AS) in 2% of adults above 65 years. Echocardiography is today the clinical standard for assessing AS. However, a cost effective and uncomplicated technique that can be used for decision support in the primary health care would be of great value. In this study, recorded phonocardiographic signals were analyzed using the first local minimum of the auto mutual information (AMI) function. The AMI method measures the complexity in the sound signal, which is related to the amount of turbulence in the blood flow and thus to the severity of the stenosis. Two previously developed phonocardiographic methods for assessing AS severity were used for comparison, the murmur energy ratio and the sound spectral averaging technique. Twenty-nine patients with suspected AS were examined with Doppler echocardiography. The aortic jet velocity was used as a reference of AS severity, and it was found to correlate with the AMI method, the murmur energy ratio and the sound spectral averaging technique with the correlation coefficient R = 0.82, R = 0.73 and R = 0.76, respectively.
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| 8. |
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| 9. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Development of sleepiness in professional truck drivers : Real‐road testing for driver drowsiness and attention warning (DDAW) system evaluation
- 2024
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Ingår i: Journal of Sleep Research. - : John Wiley & Sons. - 0962-1105 .- 1365-2869.
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Tidskriftsartikel (refereegranskat)abstract
- All new vehicle types within the European Union must now be equipped with a driver drowsiness and attention warning system starting from 2022. The specific requirements for the test procedure necessary for type approval are defined in the Annex of EU Regulation C/2021/2639. The objectives of this study were to: (i) investigate how sleepiness develops in professional truck drivers under real-road driving conditions; and (ii) assess the feasibility of a test procedure for validating driver drowsiness and attention warning systems according to the EU regulation. Twenty-four professional truck drivers participated in the test. They drove for 180 km on a dual-lane motorway, first during daytime after a normal night's sleep and then at nighttime after being awake since early morning. The results showed higher sleepiness levels during nighttime driving compared with daytime, with a faster increase in sleepiness with distance driven, especially during the night. Psychomotor vigilance task results corroborated these findings. From a driver drowsiness and attention warning testing perspective, the study design with sleep-deprived drivers at night was successful in inducing the targeted sleepiness level of a Karolinska Sleepiness Scale score of ≥ 8. Many drivers who reported a Karolinska Sleepiness Scale ≥ 8 during the drives also acknowledged feeling sleepy in the post-drive questionnaire. Reaching high levels of sleepiness on real roads during daytime is more problematic, not the least from legal and ethical perspectives as higher traffic densities during the daytime lead to increased risks.
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| 10. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Distinguishing Innocent Murmurs from Murmurs caused by Aortic Stenosis by Recurrence Quantification Analysis
- 2006
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Ingår i: ROCEEDINGS OF WORLD ACADEMY OF SCIENCE, ENGINEERING AND TECHNOLOGY, VOL 18. - Canakkale, Turkey : World Academy of Science, Engineering and Technology (W A S E T). ; , s. 40-45
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Konferensbidrag (refereegranskat)abstract
- It is sometimes difficult to differentiate between innocent murmurs and pathological murmurs during auscultation. In these difficult cases, an intelligent stethoscope with decision support abilities would be of great value. In this study, using a dog model, phonocardiographic recordings were obtained from 27 boxer dogs with various degrees of aortic stenosis (AS) severity. As a reference for severity assessment, continuous wave Doppler was used. The data were analyzed with recurrence quantification analysis (RQA) with the aim to find features able to distinguish innocent murmurs from murmurs caused by AS. Four out of eight investigated RQA features showed significant differences between innocent murmurs and pathological murmurs. Using a plain linear discriminant analysis classifier, the best pair of features (recurrence rate and entropy) resulted in a sensitivity of 90% and a specificity of 88%. In conclusion, RQA provide valid features which can be used for differentiation between innocent murmurs and murmurs caused by AS.
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| 11. |
- 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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| 12. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Eye Tracking in Driver Attention Research : How Gaze Data Interpretations Influence What We Learn
- 2021
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Ingår i: Frontiers in Neuroergonomics. - : Frontiers Media SA. - 2673-6195. ; 2:34
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Tidskriftsartikel (refereegranskat)abstract
- Eye tracking (ET) has been used extensively in driver attention research. Amongst other findings, ET data have increased our knowledge about what drivers look at in different traffic environments and how they distribute their glances when interacting with non-driving related tasks. Eye tracking is also the go-to method when determining driver distraction via glance target classification. At the same time, eye trackers are limited in the sense that they can only objectively measure the gaze direction. To learn more about why drivers look where they do, what information they acquire foveally and peripherally, how the road environment and traffic situation affect their behavior, and how their own expertise influences their actions, it is necessary to go beyond counting the targets that the driver foveates. In this perspective paper, we suggest a glance analysis approach that classifies glances based on their purpose. The main idea is to consider not only the intention behind each glance, but to also account for what is relevant in the surrounding scene, regardless of whether the driver has looked there or not. In essence, the old approaches, unaware as they are of the larger context or motivation behind eye movements, have taken us as far as they can. We propose this more integrative approach to gain a better understanding of the complexity of drivers' informational needs and how they satisfy them in the moment.
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| 13. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Förares användning av kommunikationsutrustning under färd : Del 1: Enkätstudie. Del 2: Användning enligt objektiv mätning
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Av resultaten från denna enkät är något av det mest tydliga att saker som funnits i en bil en längre tid, exempelvis att ställa in radio, använda navigationsutrustning och prata i telefon, görs i betydligt högre utsträckning än nyare saker som att skicka meddelanden, surfa på internet eller spela spel. Överlag tycks det vara låg acceptans för de nyare företeelserna och en stor andel av urvalet tycker att det är felaktigt eller olämpligt att hålla på med dessa aktiviteter. Att prata i telefon med handsfree tycks uppfattas av många som säkrare och mer lämpligt än att inte använda det. Detta avspeglas även i inställning till införandet av förbud, där en relativt stor andel accepterar att det ska vara lagligt att använda handsfreefunktioner men att annan användning av kommunikationsutrustning borde förbjudas.I den andra delen genomfördes en mätning av mobilanvändning under färd genom installerande tav en mobilapp. Den genomförda undersökningen är den första av sitt slag åtminstone i Sverige, så att den, trots vissa brister och begränsningar, kan leverera information som hittills har varit okänt. I detta del diskuteras resultaten, även i förhållande till enkätsvaren, följt av en reflektion över metoden och möjliga förbättringar, som är önskvärda inför en fortsättningsstudie.
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| 14. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Local changes in the wake electroencephalogram precedes lane departures
- 2017
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Ingår i: Journal of Sleep Research. - : Blackwell Publishing. - 0962-1105 .- 1365-2869. ; 26:6, s. 816-819
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this exploratory study is to investigate if lane departures are associated with local sleep, measured via source-localized electroencephalography (EEG) theta power in the 5-9 Hz frequency range. Thirty participants drove in an advanced driving simulator, resulting in 135 lane departures at high levels of self-reported sleepiness. These lane departures were compared to matching non-departures at the same sleepiness level within the same individual. There was no correspondence between lane departures and global theta activity. However, at the local level an increased risk for lane departures was associated with increased theta content in brain regions related to motor function.
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| 15. |
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| 16. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Noninvasive investigation of blood pressure changes using the pulse wave transit time : A novel approach in the monitoring of hemodialysis patients
- 2005
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Ingår i: Journal of Artificial Organs. - : Springer Science and Business Media LLC. - 1434-7229 .- 1619-0904. ; 8:3, s. 192-197
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Tidskriftsartikel (refereegranskat)abstract
- Severe blood pressure changes are well known in hemodialysis. Detection and prediction of these are important for the well-being of the patient and for optimizing treatment. New noninvasive methods for this purpose are required. The pulse wave transit time technique is an indirect estimation of blood pressure, and our intention is to investigate whether this technique is applicable for hemodialysis treatment. A measurement setup utilizing lower body negative pressure and isometric contraction was used to simulate dialysis-related blood pressure changes in normal test subjects. Systolic blood pressure levels were compared to different pulse wave transit times, including and excluding the cardiac preejection period. Based on the results of these investigations, a pulse wave transit time technique adapted for dialysis treatment was developed and tried out on patients. To determine systolic blood pressure in the normal group, the total pulse wave transit time was found most suitable (including the cardiac preejection period). Correlation coefficients were r = 0.80 ± 0.06 (mean ± SD) overall and r = 0.81 ± 0.16 and r = 0.09 ± 0.62 for the hypotension and hypertension phases, respectively. When applying the adapted technique in dialysis patients, large blood pressure variations could easily be detected when present. Pulse wave transit time is correlated to systolic blood pressure within the acceptable range for a trend-indicating system. The method's applicability for dialysis treatment requires further studies. The results indicate that large sudden pressure drops, like those seen in sudden hypovolemia, can be detected. © The Japanese Society for Artificial Organs 2005.
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| 17. |
- Ahlström, Christer, 1977-
(författare)
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Nonlinear phonocardiographic Signal Processing
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis work has been to develop signal analysis methods for a computerized cardiac auscultation system, the intelligent stethoscope. In particular, the work focuses on classification and interpretation of features derived from the phonocardiographic (PCG) signal by using advanced signal processing techniques.The PCG signal is traditionally analyzed and characterized by morphological properties in the time domain, by spectral properties in the frequency domain or by nonstationary properties in a joint time-frequency domain. The main contribution of this thesis has been to introduce nonlinear analysis techniques based on dynamical systems theory to extract more information from the PCG signal. Especially, Takens' delay embedding theorem has been used to reconstruct the underlying system's state space based on the measured PCG signal. This processing step provides a geometrical interpretation of the dynamics of the signal, whose structure can be utilized for both system characterization and classification as well as for signal processing tasks such as detection and prediction. In this thesis, the PCG signal's structure in state space has been exploited in several applications. Change detection based on recurrence time statistics was used in combination with nonlinear prediction to remove obscuring heart sounds from lung sound recordings in healthy test subjects. Sample entropy and mutual information were used to assess the severity of aortic stenosis (AS) as well as mitral insufficiency (MI) in dogs. A large number of, partly nonlinear, features was extracted and used for distinguishing innocent murmurs from murmurs caused by AS or MI in patients with probable valve disease. Finally, novel work related to very accurate localization of the first heart sound by means of ECG-gated ensemble averaging was conducted. In general, the presented nonlinear processing techniques have shown considerably improved results in comparison with other PCG based techniques.In modern health care, auscultation has found its main role in primary or in home health care, when deciding if special care and more extensive examinations are required. Making a decision based on auscultation is however difficult, why a simple tool able to screen and assess murmurs would be both time- and cost-saving while relieving many patients from needless anxiety. In the emerging field of telemedicine and home care, an intelligent stethoscope with decision support abilities would be of great value.
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| 18. |
- Ahlström, Christer, 1977-
(författare)
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Processing of the Phonocardiographic Signal : methods for the intelligent stethoscope
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phonocardiographic signals contain bioacoustic information reflecting the operation of the heart. Normally there are two heart sounds, and additional sounds indicate disease. If a third heart sound is present it could be a sign of heart failure whereas a murmur indicates defective valves or an orifice in the septal wall. The primary aim of this thesis is to use signal processing tools to improve the diagnostic value of this information. More specifically, three different methods have been developed:• A nonlinear change detection method has been applied to automatically detect heart sounds. The first and the second heart sounds can be found using recurrence times of the first kind while the third heart sound can be found using recurrence times of the second kind. Most third heart sound occurrences were detected (98 %), but the amount of false extra detections was rather high (7 % of the heart cycles).• Heart sounds obscure the interpretation of lung sounds. A new method based on nonlinear prediction has been developed to remove this undesired disturbance. High similarity was obtained when comparing actual lung sounds with lung sounds after removal of heart sounds.• Analysis methods such as Shannon energy, wavelets and recurrence quantification analysis were used to extract information from the phonocardiographic signal. The most prominent features, determined by a feature selection method, were used to create a new feature set for heart murmur classification. The classification result was 86 % when separating patients with aortic stenosis, mitral insufficiency and physiological murmurs.The derived methods give reasonable results, and they all provide a step forward in the quest for an intelligent stethoscope, a universal phonocardiography tool able to enhance auscultation by improving sound quality, emphasizing abnormal events in the heart cycle and distinguishing different heart murmurs.
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| 19. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Real-Time Adaptation of Driving Time and Rest Periods in Automated Long-Haul Trucking : Development of a System Based on Biomathematical Modelling, Fatigue and Relaxation Monitoring
- 2022
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1524-9050 .- 1558-0016. ; 23:5, s. 4758-4766
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Tidskriftsartikel (refereegranskat)abstract
- Hours of service regulations govern the working hours of commercial motor vehicle drivers, but these regulations may become more flexible as highly automated vehicles have the potential to afford periods of in-cab rest or even sleep while the vehicle is moving. A prerequisite is robust continuous monitoring of when the driver is resting (to account for reduced time on task) or sleeping (to account for the reduced physiological drive to sleep). The overall aims of this paper are to raise a discussion of whether it is possible to obtain successful rest during automated driving, and to present initial work on a hypothetical data driven algorithm aimed to estimate if it is possible to gain driving time after resting under fully automated driving. The presented algorithm consists of four central components, a heart rate-based relaxation detection algorithm, a camera-based sleep detection algorithm, a fatigue modelling component taking time awake, time of day and time on task into account, and a component that estimates gained driving time. Real-time assessment of driver fitness is complicated, especially when it comes to the recuperative value of in-cab sleep and rest, as it depends on sleep quality, time of day, homeostatic sleep pressure and on the activities that are carried out while resting. The monotony that characterizes for long-haul truck driving is clearly interrupted for a while, but the long-term consequences of extended driving times, including user acceptance of the key stakeholders, requires further research.
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| 20. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Road Vehicle Automation and Its Effects on Fatigue, Sleep, Rest, and Recuperation
- 2023. - 1
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Ingår i: The Handbook of Fatigue Management in Transportation. - Boca Raton : CRC Press. - 9781003213154
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Assisted and automated driving brings new challenges and opportunities when it comes to driver fatigue. With lower levels of vehicle automation, driver monotony and boredom in combination with demanding attentive monitoring leads to higher levels of fatigue, especially during the night when the sleep pressure is high. With higher levels of vehicle automation, when the driver is not required to continuously monitor the roadway and the automation system, task-related fatigue can be counteracted by engaging in non-driving-related activities. Finally, with the highest levels of vehicle automation, it may even become possible for drivers to sleep while on the move. Aside from making it possible for private car drivers to take strategic naps during a drive, this also opens up the possibility for more flexible, risk management-based, hour of service regulations for professional drivers. This chapter summarises the current state of the art on how assisted and piloted driving affects driver fatigue and how automation may facilitate recovery and recuperation from fatigue while on the move. It also covers how automated functions will impact driver monitoring systems and how new ways of counteracting driver fatigue may arise when automation is available.
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| 21. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Strategical use of peripheral vision in driving
- 2022
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Ingår i: DDI 2022 Gothenburg. - Göteborg : Safer. ; , s. 71-73
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To successfully get around in traffic it is often necessary to keep track of several relevant targets at the same time. This can be done by combining foveal and peripheral visual information sampling. Especially if no detailed input is needed, for example when confirming the absence of road users, it may be enough to use peripheral vision only. Using a driving simulator with an urban scenery, 35 participants passed three zebra crossings with a) no pedestrians nearby, b) pedestrians standing nearby and c) pedestrians nearby of whom one started walking towards the street. In the last case, all participants foveated the walking person, albeit around one third of the participants already released the throttle before the first glance at the pedestrian. The standing pedestrians were foveated in almost all instances, whereas the roadside nearby the zebra crossing without people nearby was not foveated by around a quarter of the participants. Taken together, the results indicate that peripheral vision may suffice to confirm the absence or presence of pedestrians. With people present, a glance towards them is initiated, likely to check for additional information. Throttle release before foveation is an indication that the walking pedestrian was detected as relevant with peripheral vision.
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| 22. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Technologies for Risk Mitigation and Support of Impaired Drivers
- 2022
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : IEEE. - 1524-9050 .- 1558-0016. ; 23:5, s. 4736-4738
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This editorial serves as an extended introduction to the Special Issue on Technologies for Risk Mitigation and Support of Impaired Drivers. It gives the context to recent advances in assisted and automated driving and the new challenges that arise when modern technology meets human users. The Special Issue focuses on the development of robust sensors and detection algorithms for driver state monitoring of fatigue, stress, and inattention, and on the development of personalized multimodal, user-oriented, and adaptive information, warning, actuation, and handover strategies. A summary of more recent developments serves as a motivation for each article that follows.
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| 23. |
- Ahlström, Christer, 1977-, et al.
(författare)
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The effect of an active steering system on city bus drivers’ muscle activity
- 2019
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Ingår i: International Journal of Occupational Safety and Ergonomics. - : Taylor & Francis. - 1080-3548 .- 2376-9130. ; 25:3, s. 377-385
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Tidskriftsartikel (refereegranskat)abstract
- City bus drivers spend hours driving under time pressure, in congested traffic and in a monotonous sitting position. This leads to unhealthy working conditions, especially in terms of physical and psychological stress. The aim of this study is to investigate whether an active steering system can alleviate the musculoskeletal stress involved in manoeuvring a bus. Twenty bus drivers drove a city bus equipped with the Volvo dynamic steering (VDS) support system in real traffic. Steering effort was evaluated with electromyography and with a questionnaire. Compared to baseline, VDS significantly reduced the required muscle activity by on average 15–25% while turning, and up to 68% in the part of the manoeuvre requiring maximum effort. The bus drivers believed that VDS will help reduce neck and shoulder problems, and they expressed a desire to have VDS installed in their own bus.
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| 24. |
- 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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| 25. |
- Ahlström, Christer, 1977-, et al.
(författare)
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The impact of driver sleepiness on fixation-related brain potentials
- 2020
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Ingår i: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 29:5
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Tidskriftsartikel (refereegranskat)abstract
- The effects of driver sleepiness are often quantified as deteriorated driving performance, increased blink durations and high levels of subjective sleepiness. Driver sleepiness has also been associated with increasing levels of electroencephalogram (EEG) power, especially in the alpha range. The present exploratory study investigated a new measure of driver sleepiness, the EEG fixation-related lambda response. Thirty young male drivers (23.6 +/- 1.7 years old) participated in a driving simulator experiment in which they drove on rural and suburban roads in simulated daylight versus darkness during both the daytime (full sleep) and night-time (sleep deprived). The results show lower lambda responses during night driving and with longer time on task, indicating that sleep deprivation and time on task cause a general decrement in cortical responsiveness to incoming visual stimuli. Levels of subjective sleepiness and line crossings were higher under the same conditions. Furthermore, results of a linear mixed-effects model showed that low lambda responses are associated with high subjective sleepiness and more line crossings. We suggest that the fixation-related lambda response can be used to investigate driving impairment induced by sleep deprivation while driving and that, after further refinement, it may be useful as an objective measure of driver sleepiness.
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| 26. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Thresholding distance plots using true recurrence points
- 2006
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Ingår i: Acoustics, Speech and Signal Processing, 2006. ICASSP 2006. - : IEEE. - 142440469X ; , s. 688-691
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Konferensbidrag (refereegranskat)abstract
- Recurrence plots (RP) visualize multi-dimensional state spaces and represent the recurrence of states of a system. Recurrence points can be divided into true recurrence points and false recurrence points (also called sojourn points). We introduce the true recurrence point recurrence plot, TRP, a variant of the traditional RP excluding the sojourn points. This is a cleaned up RP free from recurrence points originating from tangential motion, and hence a more robust representation of unstable periodic orbits. The method is demonstrated with three simple systems, a periodic sine wave, a quasi-periodic torus and the x-component of the chaotic Lorenz system
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| 27. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Towards a Context-Dependent Multi-Buffer Driver Distraction Detection Algorithm
- 2022
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1524-9050 .- 1558-0016. ; 23:5, s. 4778-4790
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents initial work on a context-dependent driver distraction detection algorithm called AttenD2.0, which extends the original AttenD algorithm with elements from the Minimum Required Attention (MiRA) theory. Central to the original AttenD algorithm is a time buffer which keeps track of how often and for how long the driver looks away from the forward roadway. When the driver looks away the buffer is depleted and when looking back the buffer fills up. If the buffer runs empty the driver is classified as distracted. AttenD2.0 extends this concept by adding multiple buffers, thus integrating situation dependence and visual time-sharing behaviour in a transparent manner. Also, the increment and decrement of the buffers are now controlled by both static requirements (e.g. the presence of an on-ramp increases the need to monitor the sides and the mirrors) as well as dynamic requirements (e.g., reduced speed lowers the need to monitor the speedometer). The algorithm description is generic, but a real-time implementation with concrete values for different parameters is showcased in a driving simulator experiment with 16 bus drivers, where AttenD2.0 was used to ensure that drivers are attentive before taking back control after an automated bus stop docking and depot procedure. The scalability of AttenD2.0 relative to available data sources and the level of vehicle automation is demonstrated. Future work includes expanding the concept to real-world environments by automatically integrating situational information from the vehicles environmental sensing and from digital maps.
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| 28. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Using smartphone logging to gain insight about phone use in traffic
- 2020
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Ingår i: Cognition, Technology & Work. - : Springer. - 1435-5558 .- 1435-5566. ; 22, s. 181-191
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of mobile phone usage in traffic has been studied by road-side counting, naturalistic driving data, surveillance cameras, smartphone logging, and subjective estimates via surveys. Here, we describe a custom-made smartphone logging application along with suggestions on how future such applications should be designed. The developed application logs’ start and end times of all phone interactions (mobile phone applications, incoming/outgoing phone calls and text messages, audio output, and screen activations). In addition, all movements are automatically classified into transport, cycling, walking, running, or stationary. The capabilities of the approach are demonstrated in a pilot study with 143 participants. Examples of results that can be gained from smartphone logging include prevalence in different transportation modes (here found to be 12% while driving, 4% while cycling, and 7% while walking), which apps are being used (here found to be 19% navigation, 12% talking, 12% social media, and 10% games) and on which road types (rural, urban, highway etc.). Smartphone logging was found to be an insightful complement to the other methods for assessing phone use in traffic, especially since it allows the analyses of which apps are used and where they are used, split into transportation mode and road type, all at a relatively low cost.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Andersson, Jan, 1965-, et al.
(författare)
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Bicycling during alcohol intoxication
- 2023
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Ingår i: Traffic Safety Research. - : Lund University Faculty of Engineering. - 2004-3082. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The number of bicycling fatalities was 19 450 between 2010 and 2018 in Europe. The number of bicyclists killed when intoxicated by alcohol is harder to establish given the lack of reliable data. In Sweden, drunk bicycling is socially acceptable and legal (unless reckless). This experiment aimed to investigate how alcohol intoxication affect bicycling stability performance, executive functions, and self-rated ability. The experiment was completed on a wide treadmill that allowed control of several influencing factors such as speed and physical effort. Intoxicated and sober participants bicycled on the treadmill for five 10 minute sessions. Alcohol as administered incrementally to reach a target breath alcohol concentration level of 0.8‰. Stability decreased with intoxication; especially roll rate measurements were identified as being adequate indicators of bicycling instability. Executive function was negatively affected, and ability ratings decreased due to intoxication. The intoxicated participants were aware of their reduced ability to bicycle in a safe manner on a group level but not on an individual level. However, this insight does not affect their intention to bicycle intoxicated.
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| 33. |
- 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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| 34. |
- Anund, Anna, 1964-, et al.
(författare)
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Säkerhetsförare på autonoma bussar : Uppmärksamhet och trötthet : en explorativ studie
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Försöksverksamhet och studier med små autonoma bussar i tätort blir allt vanligare och i samband med ansökan om tillstånd att bedriva sådan verksamhet krävs en säkerhetsförare ombord som kan ta över kontrollen då fordonet inte klarar sin uppgift. Det innebär i praktiken att säkerhetsföraren är ytterst ansvarig för att resan bedrivs med hög säkerhet för resande och för omgivande trafikanter. Målet med denna studie har varit att studera säkerhetsförarens arbetsmiljö och i synnerhet möjligheter att i det automatiserade fordonet agera på ett för resenärer och omgivande trafikanter säkert sätt. Studien har genomförts i Linköping i nära samarbete med mobilitetsarenan ”Ride the future”. Totalt deltog 8 förare. Datainsamlingen har varit fokuserad på säkerhetsförares vakenhet och uppmärksamhet. Studien var explorativ och förarna har inte manipulerats utan datainsamlingen har skett i samband med vanlig drift under vanliga arbetspass. Data samlades in under eftermiddagspassens första och sista timme. Resultaten från dessa har sedan jämförts. Förarnas vakenhet har mätts med självrapporterad sömnighet (KSS) och via blinkmått (blinkduration och långa blinkningar) samt hjärtfrekvensbaserade mått (hjärtfrekvensvariabilitet). Vidare har förares ögonrörelser identifierats för att beskriva hur de söker av omgivningen under körning.
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| 35. |
- 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
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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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| 36. |
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| 37. |
- Bakker, Bram, et al.
(författare)
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A Multi-Stage, Multi-Feature Machine Learning Approach to Detect Driver Sleepiness in Naturalistic Road Driving Conditions
- 2022
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : IEEE. - 1524-9050 .- 1558-0016. ; 23:5, s. 4791-4800
-
Tidskriftsartikel (refereegranskat)abstract
- Driver fatigue is a contributing factor in about 20% of all fatal road crashes worldwide. Countermeasures are urgently needed and one of the most promising and currently available approaches for that are in-vehicle systems for driver fatigue detection. The main objective of this paper is to present a video-based driver sleepiness detection system set up as a two-stage model with (1) a generic deep feature extraction module combined with (2) a personalised sleepiness detection module. The approach was designed and evaluated using data from 13 drivers, collected during naturalistic driving conditions on a motorway in Sweden. Each driver performed one 90-minute driving session during daytime (low sleepiness condition) and one session during night-time (high sleepiness condition). The sleepiness detection model outputs a continuous output representing the Karolinska Sleepiness Scale (KSS) scale from 1-9 or a binary decision as alert (defined as KSS 1-6) or sleepy (defined as KSS 7-9). Continuous output modelling resulted in a mean absolute error (MAE) of 0.54 KSS units. Binary classification of alert or sleepy showed an accuracy of 92% (sensitivity = 91.7%, specificity = 92.3%, F1 score = 90.4%). Without personalisation, the corresponding accuracy was 72%, while a standard fatigue detection PERCLOS-based baseline method reached an accuracy of 68% on the same dataset. The developed real-time sleepiness detection model can be used in the management of sleepiness/fatigue by detecting precursors of severe fatigue, and ultimately reduce sleepiness-related road crashes by alerting drivers before high levels of fatigue are reached.
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| 38. |
- Eriksson, Lars, et al.
(författare)
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Driver acceptance and performance with LDW and rumble strips assistance in unintentional lane departures
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this ViP project the focus of investigation was whether drivers more readily accept either rumble strips or an in-vehicle lane departure warning system (LDW) in unintentional lane departure situations. The results show that acceptance was high for both alternatives, but while the drivers showed more satisfaction from using the LDW, they also showed more trust in the rumble strips. Twenty-four drivers drove the VTI driving simulator SIM III in car mode with simulated rumble strips in one drive and with a simulated Volvo LDW in another drive. A forced yaw motion of the vehicle induced the unintentional lane departures. The results showed no choice in favour of the LDW or the rumble strips, but a clear preference for having a function that warns for unintentional lane departure. Several participants thought it was good to have both types of warning in parallel. Although Response completion time was shorter with the rumble strips warning, there was no difference between the warning types, neither in Time to get car back in lane nor in Lane exceedence area. Thus, there were no major overall differences between the LDW and the rumble strips as measured in the present study. The conclusion is that the drivers’ acceptance, as well as performance, was high for both the rumble strips and the LDW. The positive opinion on the need for assistance systems in unintentional lane departure when drivers are directing their visual attention away from the road is thus further strengthened.
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| 39. |
- Hjälmdahl, Magnus, et al.
(författare)
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Driving style and energy consumption with everyday use of a plug-in hybrid electric vehicle
- 2018
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Ingår i: 31st International Electric Vehicle Symposium and Exhibition, EVS 2018 and International Electric Vehicle Technology Conference 2018, EVTeC 2018. - : Society of Automotive Engineers of Japan Inc.
-
Konferensbidrag (refereegranskat)abstract
- Chargeable vehicles with focus on plug-in hybrid vehicles have become common. The impact PHEVs have on the energy consumption significantly varies with driving behaviour, charging possibilities, and the driving mission. This study investigates how PHEVs function during real driving. Questionnaires, interviews, and measurement vehicle data are evaluated. Key findings is that the fuel consumption decreases significantly at low speeds compared to a combustion engine vehicle, and that the drivers believe that they adopt the driving to the characteristics of the PHEV, but this is not found in the measurement data. The vehicle is behavious in the way the driver wants without any adaptation required.
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| 40. |
- Hult, Peter, 1964-, et al.
(författare)
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The intelligent stethoscope
- 2005
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Ingår i: EMBEC05,2005. - Prag : IFMBE.
-
Konferensbidrag (refereegranskat)
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| 41. |
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| 42. |
- Höglund, K, et al.
(författare)
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Spectral analysis of heart murmurs in boxer dogs
- 2006
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Ingår i: 16th European College of veterinary Internal medicine - Companion Animals Congress ECVIM-CA,2006.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 43. |
- Jansson, Andreas, 1989-, et al.
(författare)
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Linking gaze tracking with a simulated world
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this study was to develop a software able to link eye tracking data to simulator data, making it possible to automatically detect what the driver is looking at in the simulated world. This was achieved by merging data from a SmartEye system with data from the simulator. Thereby realtime visualisation of where the driver is looking is facilitated, and what the driver is targeting can be shown to the test leader to trigger events in the scenarios, etc. This also facilitates automatic gaze annotations that can be used in subsequent analyses when studying visual behaviour.The developed software, VIMSI, is responsible for collecting eye tracking data from SmartEye, filter and aggregate this data with data from the simulation and then send processed data to the graphics to visualize the result. The software was tested in one of VTI’s driving simulators. This initial testing of VIMSI showed that the software is capable of visualising what the driver is looking at in real time. The software also makes it possible to log data from the test drives which can be useful when studying driver behaviour. To improve the functionality of VIMSI, it is necessary to consider using UDP instead of IPC when directing data from the VIMSI software to the graphics engine VISIR. This will enable the use of another software, ScenarioReplay, developed at VTI for replaying test drives. A proper configuration and calibration of the SmartEye cameras is necessary to achieve high quality of the data from the SmartEye Pro software, which is a precondition for VIMSI.
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| 44. |
- Johansson, Anders, 1972-, et al.
(författare)
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Pulse wave transit time for monitoring respiration rate
- 2006
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 44:6, s. 471-478
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring. © International Federation for Medical and Biological Engineering 2006.
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| 45. |
- Jägerbrand, Annika K., et al.
(författare)
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Speed reduction effects over distance of animal-vehicle collision countermeasures – a driving simulator study
- 2018
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Ingår i: European Transport Research Review. - : Springer Publishing Company. - 1867-0717 .- 1866-8887. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study examined if speed reduction effects from animal-vehicle collision (AVC) countermeasures are merely local or do extend to a wider area, and what implications the results have on road planning practice regarding AVCs.Methods: Twenty-five drivers drove repeatedly on a 9-km long road stretch in a high-fidelity driving simulator. The development of vehicle speed in the surrounding of an automatic speed camera, a wildlife warning sign and a radio message, were investigated in a full factorial within-subject experiment. The factors wildlife fence (with/without) and forest (dense/open landscape) were also included.Results: The radio warning message had the largest influence on vehicle speed with a speed reduction of 8 km/h that lasted beyond 1 km and 2 km after the implementation. Eighty-eight per cent of the drivers reported being made extra aware of AVC due to the radio message, which was also associated with stress, insecurity and unsafety. The warning sign reduced vehicle speed by 1.5 km/h, but speed reductions were not significantly reduced 1 km after the implementation. Only 8 % of the drivers felt insecure/unsafe after passing the wildlife warning sign, explaining its limited impact on speed. There were no main effects of the automatic speed camera on vehicle speed at longer distances after implementation.Conclusions: We recommend that AVC countermeasures should be of various design, occur at various segments along the road, and preferably be adaptive and geo-localized to minimize habituation effects on drivers.
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| 46. |
- Kircher, Katja, 1973-, et al.
(författare)
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A comparison of glance coding approaches for driver attention assessment
- 2024
-
Ingår i: Transportation Research Part F. - : Elsevier. - 1369-8478 .- 1873-5517. ; 100, s. 243-253
-
Tidskriftsartikel (refereegranskat)abstract
- Eye tracking is a common tool to assess drivers’ attentional state, either in real-time with the goal to prevent incidents, or offline, to understand underlying processes. While seemingly objective, eye tracking data can be coded and interpreted in different ways, which can have substantial effects on the results. The objective of this paper is to highlight and discuss the possibilities and limitations of three different approaches to code glance data: the direction-based encoding, the target-based approach, and the purpose-based approach. The direction-based coding scheme describes glances relative to the direction of travel. The target-based approach classifies the glance targets into different categories. The purpose-based approach needs additional layers of information to deduce the reason for the glance. This information encompasses road layout, traffic rules, and the presence and relevance of other traffic.Data from a field study with 23 participants driving an instrumented vehicle on an urban route was used to illustrate differences between the three methods. The results showed that the coding approach clearly affected the interpretation of the measured glance data. A purely target-based approach is limited by its inability to account for spare visual capacity and that also the absence of a target constitutes valuable information, and a purely direction-based approach does not account for the need to scan areas located off forward. The purpose-based approach requires contextual information that can be cumbersome to integrate. Regardless of the approach used, additional layers of contextual information increase understanding and interpretability, potentially at the cost of increased complexity. The three approaches are suitable for different contexts and their feasibility also depends on the availability of additional data. A key message is that context awareness improves the accuracy of driver attention monitoring and inattention identification.
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| 47. |
- Kircher, Katja, 1973-, et al.
(författare)
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Aktivt resande och uppmärksamhet : vilka krav ställer trafikmiljön på barns och ungdomars uppmärksamhet?
- 2023
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet undersöker hur barns ålder påverkar deras förmåga till uppmärksamhet i trafiken när de cyklar och går till skolan. Datamaterialet utgörs av svaren på en enkät om skolvägar (432 elever från 45 olika skolor), en semi-kontrollerad fältstudie där barnens beteende på väg till skolan loggades (20 fotgängare, 42 cyklister), samt en observationsstudie i olika korsningar (609 fotgängare, 277 cyklister). Resultaten tyder på att trafikmiljön snarare än barns ålder påverkar hur väl kraven på uppmärksamhet uppfylls i en situation. Detta går hand i hand med tidigare forskning som visar att det till stor del beror på trafikmiljön om det är säkert att vistas där, och att det inte finns någon allmän åldersgräns för när det är lämpligt att röra sig i trafiken. Snarare spelar utformningen av miljön en betydande roll för hur väl kraven på uppmärksamhet kan hanteras. Det visade sig också ha betydelse om eleverna rörde sig i grupp eller själva och hur grupperna var sammansatta både i termer av ålder och färdsätt. Resultaten från datainsamlingarna visar att utformning av infrastruktur, vart man är på väg, trafikslag och trafikregler påverkar vilka områden som är viktiga att titta åt för att säkerställa att vägen är fri. Genom att lägga till sådan information i ett geografiskt informationssystem (GIS) kan man systematiskt undersöka hur förändringar i infrastrukturen påverkar kraven på uppmärksamheten för olika trafikslag och i olika situationer. En första implementation har gjorts i projektet för att visa på potentialen för ett GIS-verktyg som tar hänsyn till krav på uppmärksamhet. Ett sådant verktyg skulle underlätta för planerare och andra som gestaltar trafikmiljöer så att dessa kan utformas på ett sätt som är tryggt och trafiksäkert för barn och unga. Sammantaget visar resultaten att trafikmiljön snarare än ålder och kognitiv mognad sätter ramarna för vem som kan eller bör vistas i transportsystemet. Utgångspunkten att barn inte är kapabla att vistas i trafiken behöver nyanseras.
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| 48. |
- Kircher, Katja, 1973-, et al.
(författare)
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Children and youngster's gaze behaviour when cycling in familiar environments
- 2023
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Ingår i: Journal of Cycling and Micromobility Research. - : Elsevier. - 2950-1059. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- Active travel is beneficial for individuals and society in many ways. As transportation habits are formed at a young age, active school transport should be promoted. However, young children are often portrayed as not being able to cope with the demands traffic imposes on them. Most studies tend to confirm the notion that older children perform better than younger children, however, they are usually conducted in controlled environments that are unfamiliar to the participants. Here, 28 participants in two age groups (6–12 and 13–18 years) cycled their usual way to school to guarantee familiarity with the environment. They wore eye trackers, and the surroundings were filmed by a camera on the handlebars and by another camera mounted on the bicycle of an experimenter, who followed the participant. For each trip, all attentional target areas were identified based on infrastructure layout, traffic rules and turning direction. It was coded whether the children monitored these areas. Additionally, glance targets and glance purpose were coded. More than 80 % of all target areas were monitored. Regardless of age, a higher number of simultaneous target areas increased the likelihood that some relevant target areas were missed. The glance distribution across different types of target areas did not vary between the age groups. An increase in the number of simultaneous target areas led to a decrease in spare visual capacity and an increase in glances dedicated to checking for traffic. Overall, children in both age groups were generally attentive in their familiar environment. Difficulties were associated with a higher number of simultaneous target areas. A more controlled setup is needed to identify potentially modifying factors, and a comparison with adults is needed to for a fair valuation of the children’s performance.
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| 49. |
- Kircher, Katja, 1973-, et al.
(författare)
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Cyclist efficiency and its dependence on infrastructure and usual speed
- 2018
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Ingår i: Transportation Research Part F. - : Elsevier Ltd. - 1369-8478 .- 1873-5517. ; 54, s. 148-158
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Tidskriftsartikel (refereegranskat)abstract
- Bicyclists are a heterogeneous group, with varying abilities, traffic education and experience. While efficiency was identified as an important factor on utility bicycle trips, it might be traded for experienced safety, for example by choosing different pathways in a given situation, or by relinquishing one's right of way. In a semi-controlled study with 41 participants, a grouping was made according to self-reported riding speed in relation to other cyclists. The participants cycled twice along a 3 km inner-city route, passing four intersections with different priority rules. The cyclists were free to choose how to negotiate the intersections. Speed and the traffic surroundings were recorded via gps and cameras on the bike of the participant and of a following experimenter. For each cyclist, the ‘base’ speed on undisturbed segments was determined as reference. Based on this, the efficiency in different types of intersections was computed per cyclist group. It turned out that infrastructural aspects, cyclist group and the presence and behaviour of interacting traffic influenced cyclist efficiency. Faster cyclists were delayed more when the infrastructure required a stop regardless of the traffic situation, like at a red traffic light or a stop sign. The members of the so-called ‘comfort cyclists’ group were delayed the most in a roundabout with mixed traffic, where many chose to get off their bike and walk. In a society working for equality of access to the transport system, it is recommended to develop solutions that consider and accommodate the behaviours of different cyclist groups when planning bicycling infrastructure.
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- Kircher, Katja, 1973-, et al.
(författare)
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Cyklisters interaktion med extrautrustning, infrastrukturen och andra trafikanter : En semi-kontrollerad fältstudie
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Hur cyklister interagerar med infrastrukturen, och hur de integrerar utförandet av extrauppgifter, hänger ihop med den omgivande trafiksituationen och cyklistens egenskaper. För att studera sambanden närmare utfördes en semi-kontrollerad fältstudie med 41 cyklister, som tillhörde olika cyklistgrupper med avseende på deras vanliga hastighet under transportresor. Hastighet, blickriktning och taktiskt beteende som spårval och interaktion med inkommande textmeddelanden loggades, medan cyklisterna tillryggalade en sträcka i innerstaden på 6 kilometer. Intervjuer och tänka-högt protokoll samt filmning från olika perspektiv användes också.Det var vanligt för cyklister att ignorera inkommande textmeddelanden, en tredjedel besvarades direkt under cykling. De textmeddelanden som hanterades under cykling ledde inte till ökade brister i uppmärksamhet eftersom cyklisterna anpassade hanterandet efter omgivningen. Interaktionen med telefonen skilde sig inte nämnvärt mellan cyklistgrupperna. Däremot påverkade infrastrukturen de olika cyklisttyperna på olika sätt, där snabbare cyklister upplevde en större fördröjning, där infrastrukturen tvingar fram stopp, medan komfortcyklister fördröjdes mest i en otydligt utformad cirkulationsplats. Det kom även fram att trottoarcykling är vanligt förekommande och främst ett uttryck av upplevd osäkerhet i blandtrafik med bilar. Det är alltså viktigt att ta hänsyn till olika behov bland cyklisterna när infrastruktur utformas, så att inga irritationer, osäkerheter eller konflikter uppstår.
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