Christer Ahlstrom

Christer Ahlstrom
Swedish National Road and Transport Research Institute | VTI

PhD

About

95
Publications
22,465
Reads
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1,900
Citations
Introduction
Working as a Senior Researcher at the Swedish National Road and Transport Research Institute (VTI) with acquisition, processing and analysis of data, with particular interest in biomedical engineering aspects of driver inattention and driver sleepiness. Also holds a position as an associate professor in biomedical signal processing at the Department of Biomedical Engineering at Linköping University. Key proficiencies include an ability to extract valuable information from cluttered data sets and out-of-the-box thinking for signal and data analysis design.
Additional affiliations
June 2018 - present
Linköping University
Position
  • Professor (Associate)
August 2008 - present
Swedish National Road and Transport Research Institute
Position
  • Senior Researcher
August 2004 - July 2008
Örebro University Hospital
Position
  • Research Administrator

Publications

Publications (95)
Article
Full-text available
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 distr...
Article
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...
Article
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 s...
Article
Full-text available
Objective: The aim of this review is to identify how visual occlusion contributes to our understanding of attentional demand and spare visual capacity in driving and the strengths and limitations of the method. Background: The occlusion technique was developed by John W. Senders to evaluate the attentional demand of driving. Despite its utility,...
Article
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...
Article
Full-text available
The objective of this study was to compare the development of sleepiness during manual driving versus level 2 partially automated driving, when driving on a motorway in Sweden. The hypothesis was that partially automated driving will lead to higher levels of fatigue due to underload. Eighty-nine drivers were included in the study using a 2 × 2 desi...
Article
Objective.The objective of this paper is to present a driver sleepiness detection model based on electrophysiological data and a neural network consisting of convolutional neural networks and a long short-term memory architecture.Approach.The model was developed and evaluated on data from 12 different experiments with 269 drivers and 1187 driving s...
Article
Full-text available
With encounters between trucks and cyclists still being a major safety issue and physical as well as technological improvements far from ubiquitous implementation, training truck drivers in anticipatory driving to improve their interaction with cyclists may be a way forward. After a baseline drive in an urban environment, truck drivers inexperience...
Article
One of the more hazardous situations for a bicyclist is to go straight on in an intersection where a motor vehicle is turning right, and especially so when heavy vehicles are involved. The aim of this study was to investigate truck drivers’ speed choice, gaze behaviour and interaction strategies in relation to vulnerable road users (VRU) when turni...
Article
Full-text available
Driver sleepiness is a contributing factor in many road fatalities. A long-standing goal in driver state research has therefore been to develop a robust sleepiness detection system. It has been suggested that various heart rate variability (HRV) metrics can be used for driver sleepiness classification. However, since heart rate is modulated not onl...
Article
Full-text available
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 app...
Article
Even though often travelling on the same roads, it has been shown that cyclists and car drivers interpret their environment differently, which can lead to misunderstandings and collisions. Based on the Minimum Required Attention (MiRA) theory and the Salience, Effort, Expectancy, Value (SEEV) model, it is investigated whether the attentional requir...
Article
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...
Article
Objective To assess the attentional demand of different contextual factors in driving. Background The attentional demand on the driver varies with the situation. One approach for estimating the attentional demand, via spare capacity, is to use visual occlusion. Method Using a 3 × 5 within-subjects design, 33 participants drove in a fixed-base sim...
Article
Objective The present study strove to distinguish traffic-related glances away from the forward roadway from non-traffic-related glances while assessing the minimum amount of visual information intake necessary for safe driving in particular scenarios. Background Published gaze-based distraction detection algorithms and guidelines for distraction...
Conference Paper
Approximately 20-30% of all road fatalities are related to driver sleepiness. A long-lasting goal in driver state research has therefore been to develop a robust sleepiness detection system. Since the alertness level is reflected in autonomous nervous system activity, it has been suggested that various heart rate variability (HRV) metrics can be us...
Article
Full-text available
The first in-depth study on the use of electrocardiogram and electrooculogram for subject-dependent classification in driver sleepiness/fatigue under realistic driving conditions is presented in this work. Since acquisitions in simulated environments may be misleading for sleepiness assessment, performing studies on road are required. For that purp...
Article
Full-text available
Cyclists’ use of mobile phones in traffic has typically been studied in controlled experiments. How cyclists adapt their behaviour when they are not limited to a certain set of behaviours has not been investigated to any large extent. The aims of this study are to explore how cyclists adapt when texting and listening to music in a complex urban env...
Article
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 deprive...
Article
Full-text available
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...
Article
Objective: To investigate the influence of prior experience with Level 2 automation on additional task performance during manual and Level 2 partially automated driving. Background: Level 2 automation is now on the market, but its effects on driver behavior remain unclear. Based on previous studies, we could expect an increase in drivers’ engagem...
Article
Objective To investigate the extent of a driver’s mental model with irrevocable visual occlusion and analysing the distance to crash. Background Drivers have a mental model of the immediate surroundings which allows them to predict their own as well as others’ travel paths. To navigate safely through traffic, this mental model has to be updated fr...
Article
The objective of this paper is to investigate if signal analysis and machine learning can be used to develop an accurate sleepiness warning system. The developed system was trained using the supposedly most reliable sleepiness indicators available, extracted from electroencephalography, electrocardiography, electrooculography, and driving performan...
Article
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 stud...
Article
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 if an active steering system can alleviate the musculoskeletal stress involved in manoeuvri...
Article
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...
Article
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 o...
Article
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 arti...
Article
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,...
Article
IntroductionThe 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...
Article
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 tim...
Article
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. T...
Article
The ability to assess the current attentional state of the driver is important for many aspects of driving, not least in the field of partial automation for transfer of control between vehicle and driver. Knowledge about the driver’s attentional state is also necessary for the assessment of the effects of additional tasks on attention. The objectiv...
Article
While in-vehicle eco-driving support systems have the potential to reduce greenhouse gas emissions and save fuel, they may also distract drivers, especially if the system makes use of a visual interface. The objective of this study is to investigate the visual behaviour of drivers interacting with such a system, implemented on a five-inch screen mo...
Article
Objective: To propose a driver attention theory based on the notion of driving as a satisficing and partially self-paced task and, within this framework, present a definition for driver inattention. Background: Many definitions of driver inattention and distraction have been proposed, but they are difficult to operationalize, and they are either...
Article
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...
Article
Semi-controlled studies provide a hybrid approach in between controlled experiments and naturalistic driving studies. As in controlled experiments, the researcher can assign participants to groups, select the route and define the tasks, but the participants are given more freedom when it comes to . if, when, where and . how to perform the tasks. In...
Conference Paper
The electroencephalogram (EEG) is one of the most reliable measures of sleepiness. The recorded biopotentials are however of very low amplitude, so when the EEG is used to assess sleepiness in active individuals (drivers) in a noisy environment (the vehicle), artifact handling is of utmost importance. This abstract introduces a new automated EEG ar...
Article
Purpose 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). Methods Forty raters assessed 54 video-clips showing drivers with varying levels of sleepiness. Th...
Article
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 provid...
Article
Full-text available
Animal vehicle collisions (AVC's) have large economic, medical and ecological consequences but have rarely been studied with respect to driver behaviour. The aim of this study was to investigate different AVC-relevant landscape settings (vegetation cover), with and without game fencing and in combination with encountering moose. Twenty-five partici...
Article
The increasing prevalence of mobile phone usage while cycling has raised concerns, even though the number of cyclists involved in accidents does not increase at a comparable rate. A reason for this may be how cyclists adapt travelling speed and task execution to the current traffic situation. The aim of this study is to investigate speed adaptation...
Article
Full-text available
Purpose To examine eye tracking data and compare visual behavior in individuals with normal hearing (NH) and with moderate hearing loss (HL) during two types of driving conditions: normal driving and driving while performing a secondary task. Methods 24 participants with HL and 24 with NH were exposed to normal driving and to driving with a seco...
Article
Full-text available
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 apnoea. Identification of sleep-related symptoms may help drivers determine their sleepiness, eye symptoms in particular show promise. Sixteen participants...
Article
Automatic eco-driving advice has the potential to improve fuel economy and reduce emissions. However, providing eco-driving information to the driver will inevitably draw attention away from the driving task. The objective of this research is to investigate the effects of intermittent versus continuous visual eco-driving information on glance behav...
Article
Full-text available
Objective: The study examines how drivers experience a conventional W-beam guardrail (metal crash barrier) along both sides of narrow versus wider roads (single carriageway with 2 lanes) in terms of stress, feelings, and driving patterns and whether subjective experience concurs with the actual driving patterns captured by the quantitative data....
Article
Full-text available
According to the literature, landscape (panoramas, heritage objects e.g. landmarks) affects people in various ways. Data are primarily developed by asking people (interviews, photo sessions, focus groups) about their preferences, but to a lesser degree by measuring how the body reacts to such objects. Personal experience while driving a car through...
Article
Full-text available
Objective: There is an increase in electronic advertising billboards along major roads, which may cause driver distraction due to the highly conspicuous design of the electronic billboards. Yet limited research on the impact of electronic billboards on driving performance and driver behavior is available. The Swedish Transport Administration recen...
Article
Driver distraction is a contributing factor to many crashes; therefore, a real-time distraction warning system should have the potential to mitigate or circumvent many of these crashes. The objective of this paper is to investigate the usefulness of a real-time distraction detection algorithm called AttenD. The evaluation is based on data from an e...
Article
Driver sleepiness contributes to a considerable proportion of road accidents, and a fit-for-duty test able to measure a driver’s 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) a...
Article
Driver distraction is a contributing factor to many crashes, and a real-time distraction warning system has the potential to mitigate or circumvent many of these crashes. The objective of this chapter is to describe in detail the distraction detection algorithm AttenD and explain the theory underlying different design choices. Future aspects and di...
Conference Paper
Using induced unintentional lane departure (ULD) in an advanced driving simulator, we investigated car drivers’ acceptance of rumble strips and lane departure warning system (LDW), respectively, and driving performance with each of these warning types. Twenty-four participants drove with simulated rumble strips in one trial and with a simulated LDW...
Article
The crash risk in tunnels is lower than on the open road network, but the consequences of a crash are often severe. Proper tunnel design is one measure to reduce the likelihood of crashes, and the objective of this work is to investigate how driving performance is influenced by design factors, and whether there is an interaction with secondary task...
Article
Driver distraction and driver inattention are frequently recognized as leading causes of crashes and incidents. Despite this fact, there are few methods available for the automatic detection of driver distraction. Eye tracking has come forward as the most promising detection technology, but the technique suffers from quality issues when used in the...
Article
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 tr...
Article
Full-text available
The aim of this study was to describe the effects of sleep loss on behavioural and subjective indicators of sleepiness on a road containing a milled rumble strip in the centre of the lane. Particular attention was paid to behavioural and subjective indicators of sleepiness when using the centre lane rumble strip, and to possible erratic driving beh...
Article
Full-text available
VTI was commissioned by the Swedish Government to compile relevant research on mobile phone and other communication device usage whilst driving. Thus, a sub-set of those activities that can distract a driver in traffic are treated in the compilation. A review of several hundred publications reveals that the topic is very complex. Even though a lar...
Article
Full-text available
Many incidents and crashes can be attributed to driver distraction, and it is essential to learn how to detect distraction in order to develop efficient countermeasures. A number of distraction detection algorithms have been developed over the years, and the objective of this paper is to summarize available approaches and to describe these algorith...
Article
Full-text available
When using eye movements to determine the state of a car driver it is important that the eye tracker is robust, unobtrusive, inexpensive and fully automatic. The objectives of this study are to compare the performance of a one-camera system with a three-camera system and to investigate if the accuracy and availability of the one-camera system is su...
Article
Full-text available
Behavioral variables are often used as performance indicators (PIs) of visual or internal distraction induced by secondary tasks. The objective of this study is to investigate whether visual distraction can be predicted by driving performance PIs in a naturalistic setting. Visual distraction is here defined by a gaze based real-time distraction det...
Article
To investigate use of signal analysis of heart sounds and murmurs in assessing severity of mitral valve regurgitation (mitral regurgitation [MR]) in dogs with myxomatous mitral valve disease (MMVD). 77 client-owned dogs. Cardiac sounds were recorded from dogs evaluated by use of auscultatory and echocardiographic classification systems. Signal anal...
Article
Full-text available
Patients have reported that they perceive their own heart sounds differently after open cardiac surgery than before the surgery. The present study was designed to investigate whether changes in heart sounds can be quantitatively measured. Heart sounds were recorded from 57 patients undergoing coronary artery bypass graft (CABG) surgery and from a c...
Article
Full-text available
Percent road centre (PRC) is a performance indicator which is sensitive to driver distraction. The original definition of PRC is based on fixation data extracted from eye movement recordings, but it has also been suggested that PRC can be determined directly from the gaze data without segmenting it into saccades and fixations. The primary aim of th...
Article
Full-text available
Driver distraction is a field which has received increasing attention in the last years, especially after it became evident that distraction is a major factor contributing to road casualties. Monitoring, detecting and limiting driver distraction could contribute significantly to improve road traffic safety. With the introduction of novel unobtrusiv...
Chapter
We have developed a physiological signal platform where presently phonocardiographic (PCG) and electrocardiographic (ECG) signals can be acquired and on which our signal analysis techniques can be implemented. The platform can also be used to store patient data, to enable comparison over time and invoke distance consultation if necessary. Our studi...