| 1. |
- Engström, Johan A Skifs, 1973, et al.
(författare)
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Adaptive behavior in the simulator: Implications for active safety system evaluation
- 2011
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Ingår i: Handbook of Driving Simulation for Engineering, Medicine, and Psychology. - 9781420061017 ; , s. 41-1-41-16-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The Problem. Driving is, most of the time, a self-paced task where drivers proactively control the driving situation, based on their expectations of how things will develop in the near future. Crashes are typically associated with unexpected events where this type of proactive adaptation failed in one way or another. These types of scenarios are the main targets for active safety systems. In evaluation studies, drivers’ responses to expected events may be qualitatively different from responses to similar, but unexpected, events. Hence, creating artificial active safety evaluation scenarios that truly represent the targeted real-world scenarios is a difficult challenge. Role of Driving Simulators. Driving simulators offer great possibilities to test active safety systems with real drivers in specific target scenarios under tight experimental control. However, in simulator studies, experimental control generally has to be traded against realism. The objective of this chapter is to address some key problems related to driver expectancy and associated adaptive behavior in the context of simulator-based active safety system evaluation. Key Results of Driving Simulator Studies. The chapter briefly reviews common types of adaptive driver strategies found in the literature and proposes a general conceptual framework for describing adaptive driver behavior. Based on this framework, some key challenges in dealing with these types of issues in simulator studies are identified and potential solutions discussed. Scenarios and Dependent Variables. Key variables representing adaptive driver behavior include the selection of speed, headway, and lane position as well as the allocation of attention and effort. It will never be possible to create artificial simulator scenarios for active safety evaluation that perfectly match their real-world counterparts, but there are several means that could be used to reduce the discrepancy. Problems with expectancy and resulting adaptive behavior may at least be partly overcome by various means to “trick” drivers into critical situations, several of which are addressed in the chapter. Platform Specificity and Equipment Limitations. The issues discussed in this chapter should apply across all types of driving simulator platforms. However, some of the proposed methods for tricking drivers into critical situations may require specific simulator features, such as a motion base.
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| 2. |
- Engström, Johan A Skifs, 1973, et al.
(författare)
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Effects of working memory load and repeated scenario exposure on emergency braking performance
- 2010
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Ingår i: Human Factors. - : SAGE Publications. - 1547-8181 .- 0018-7208. ; 52:5, s. 551-559
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The objective of the present study was to examine the effect of working memory load on drivers' responses to a suddenly braking lead vehicle and whether this effect (if any) is moderated by repeated scenario exposure. Background: Several experimental studies have found delayed braking responses to lead vehicle braking events during concurrent performance of nonvisual, working memory-loading tasks, such as hands-free phone conversation. However, the common use of repeated, and hence somewhat expected, braking events may undermine the generalizability of these results to naturalistic, unexpected, emergency braking scenarios. Method: A critical lead vehicle braking scenario was implemented in a fixed-based simulator. The effects of working memory load and repeated scenario exposure on braking performance were examined. Results: Brake response time was decomposed into accelerator pedal release time and accelerator-to-brake pedal movement time. Accelerator pedal release times were strongly reduced with repeated scenario exposure and were delayed by working memory load with a small but significant amount (178 ms). The two factors did not interact. There were no effects on accelerator-to-brake pedal movement time. Conclusion:The results suggest that effects of working memory load on response performance obtained from repeated critical lead vehicle braking scenarios may be validly generalized to real world unexpected events. Application: The results have important implications for the interpretation of braking performance in experimental settings, in particular in the context of safety-related evaluation of in-vehicle information and communication technologies. © 2010, Human Factors and Ergonomics Society.
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| 3. |
- Kircher, Katja, 1973-, et al.
(författare)
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Secondary Task Workload Test Bench – 2TB : final report
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The main aim of this study was to investigate a selection of commonly used performance indicators (PIs) that have been reported to be sensitive to distraction and workload. More specifically, the PIs were tested for their ability to differentiate between task modalities (visual, cognitive and haptic) and task difficulty (easy, medium and hard). It was investigated whether possible differences were constant across two traffic situations (with/without lead vehicle) and two driving simulators. The experiment was conducted in the VTI Driving Simulator III, an advanced moving-base simulator, and in the Volvo Car Corporation driving simulator, an advanced fixed-base simulator. Both simulators were equipped with Smart Eye Pro eye tracking systems. A visual, a cognitive and a haptic secondary task were chosen to test the ability of the PIs to distinguish between the tasks’ loading on different modalities. Some of the main results from the study were:There were only minor differences between the two simulators for driving behaviour as described by longitudinal PIs. There was no overall offset, and the main difference was that the visual task led to stronger speed reductions in the moving-base simulator, which influenced both the mean speed and the speeding index.Regarding lateral PIs, major differences between the two simulators were found, both as a general offset and for those factor combinations that include modality and task difficulty level.With the visual or the haptic task active, the drivers positioned themselves further to the left and the variation in lateral position was higher in the fixed-base simulator.The number of lane crossings did not differ considerably between the simulators, but the lane departure area was larger on average in the fixed-base simulator, again influenced by modality, with the largest lane departure areas for the visual task, and in the case of the fixed-base simulator for the haptic task as well.Most of the eye movement related PIs had a general offset between the simulators. The drivers in the fixed-base simulator accumulated more time with their eyes off the road, especially during the visual and the cognitive tasks, while the drivers in the moving-base simulator cast longer single glances at the display.
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| 4. |
- Ljung Aust, Mikael, 1973, et al.
(författare)
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A conceptual framework for requirement specification and evaluation of active safety functions
- 2011
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Ingår i: Theoretical Issues in Ergonomics Science. - : Informa UK Limited. - 1464-536X .- 1463-922X. ; 12:1, s. 44-65
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Tidskriftsartikel (refereegranskat)abstract
- Active safety functions intended to prevent vehicle crashes are becoming increasingly prominent in traffic safety. Successful evaluation of their effects needs to be based on a conceptual framework, i.e. agreed-upon concepts and principles for defining evaluation scenarios, performance metrics and pass/fail criteria. The aim of this paper is to suggest some initial ideas toward such a conceptual framework for active safety function evaluation, based on a central concept termed 'situational control'. Situational control represents the degree of control jointly exerted by a driver and a vehicle over the development of specific traffic situations. The proposed framework is intended to be applicable to the whole evaluation process, from 'translation' of accident data into evaluation scenarios and definition of evaluation hypotheses, to selection of performance metrics and criteria. It is also meant to be generic, i.e. applicable to driving simulator and test track experiments as well as field operational tests.
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| 5. |
- Ljung Aust, Mikael, 1973, et al.
(författare)
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Effects of forward collision warning and repeated event exposure on emergency braking
- 2013
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Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478. ; 18, s. 34-46
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Tidskriftsartikel (refereegranskat)abstract
- Many experimental studies use repeated lead vehicle braking events to study the effects of forward collision warning (FCW) systems. It can, however, be argued that the use of repeated events induce expectancies and anticipatory behaviour that may undermine validity in terms of generalisability to real-world, naturalistic, emergency braking events. The main objective of the present study was to examine to what extent the effect of FCW on response performance is moderated by repeated exposure to a critical lead vehicle braking event. A further objective was to examine if these effects depended on event criticality, here defined as the available time headway when the lead vehicle starts to brake. A critical lead vehicle braking event was implemented in a moving-base simulator. The effects of FCW, repeated event exposure and initial time headway on driver response times and safety margins were examined. The results showed that the effect of FCW depended strongly on both repeated exposure and initial time headway. In particular, no effects of FCW were found for the first exposure, while strong effects occurred when the scenario was repeated. This was interpreted in terms of a switch from closed-loop responses triggered reactively by the situation, towards an open-loop strategy where subjects with FCW responded proactively directly to the warning. It was also found that initial time headway strongly determined response times in closed-loop conditions but not in open-loop conditions. These results raise a number of methodological issues pertaining to the design of experimental studies with the aim of evaluating the effects of active safety systems. In particular, the implementation of scenario exposure and criticality must be carefully considered.
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| 6. |
- Ljung Aust, Mikael, 1973, et al.
(författare)
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Manual for DREAM version 3.2
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Driving Reliability and Error Analysis Method (DREAM) is based on the Cognitive Reliability and Error Analysis Method (CREAM; Hollnagel, 1998). CREAM was developed to analyse accidents within process control domains such as nuclear power plants and train operation, and DREAM is an adaptation of CREAM to suit the road traffic domain. The purpose of DREAM is to make it possible to systematically classify and store accident and incident causation information. This means that DREAM, like all other methods for accident/incident analysis, is not a provider but an organiser of explanations. For any of the contributing factor categories available in DREAM to be used, it must be supported by relevant empirical information. DREAM in itself cannot tell us why accidents happen (if it could, we would need neither on-scene investigations nor interviews).DREAM includes three main components: an accident model, a classification scheme and a detailed procedure description which step by step goes through what needs to be done in order to perform a DREAM analysis on an investigated accident/incident. Below, the accident model will be given more detailed descriptions. After this follows a description of the classification scheme, and then comes the analysis process, including example cases and recommendations for how to do the categorisation in certain typical scenarios.
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| 7. |
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| 8. |
- Habibovic, Azra, 1982, et al.
(författare)
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Driver behavior in car-to-pedestrian incidents: An application of the Driving Reliability and Error Analysis Method (DREAM)
- 2013
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 50, s. 554-565
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Tidskriftsartikel (refereegranskat)abstract
- To develop relevant road safety countermeasures, it is necessary to first obtain an in-depth understanding of how and why safety-critical situations such as incidents, near-crashes, and crashes occur. Video-recordings from naturalistic driving studies provide detailed information on events and circumstances prior to such situations that is difficult to obtain from traditional crash investigations, at least when it comes to the observable driver behavior. This study analyzed causation in 90 video-recordings of car-to-pedestrian incidents captured by onboard cameras in a naturalistic driving study in Japan. The Driving Reliability and Error Analysis Method (DREAM) was modified and used to identify contributing factors and causation patterns in these incidents. Two main causation patterns were found. In intersections, drivers failed to recognize the presence of the conflict pedestrian due to visual obstructions and/or because their attention was allocated towards something other than the conflict pedestrian. In incidents away from intersections, this pattern reoccurred along with another pattern showing that pedestrians often behaved in unexpected ways. These patterns indicate that an interactive advanced driver assistance system (ADAS) able to redirect the driver's attention could have averted many of the intersection incidents, while autonomous systems may be needed away from intersections. Cooperative ADAS may be needed to address issues raised by visual obstructions.
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| 9. |
- Ljung Aust, Mikael, 1973, et al.
(författare)
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Causation patterns and data collection blind spots for fatal intersection accidents in Norway
- 2010
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Ingår i: 4:th International Conference ESAR - Expert Symposium on Accident Research, Hannover, Germany.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Norwegian fatal intersection accidents from the years 2005-2007 were analysed to identify any causation patternsamong their underlying contributing factors, and also to evaluate whether the data collection and documentation proceduresused by the Norwegian in-depth investigation teams produces the information necessary to perform causation patternanalysis. A total of 28 fatal accidents were analysed. Details on crash contributing factors for each driver in each crash werefirst coded using the Driving Reliability and Error Analysis Method (DREAM), and then aggregated based on whether thedriver was going straight or turning. Analysis results indicate that turning drivers to a large extent are faced with perceptiondifficulties and unexpected behaviour from the primary conflict vehicle, while at the same time trying to negotiate ademanding traffic situation. Drivers going straight on the other hand have less perception difficulties. Instead, their mainproblem is that they largely expect turning drivers to yield. When this assumption is violated, they are either slow to react ordo not react at all. Contributing factors often pointed to in literature, e.g. high speed, drugs and/or alcohol and inadequatedriver training, played a role in 12 of 28 accidents. While this confirms their prevalence, it also indicates that most driversend up in these situations due to combinations of less auspicious contributing factors.In terms of data collection and documentation, information on blunt end factors (those more distant in time/space, yetimportant for the development of events) was more limited than information on sharp end factors (those close in time/spaceto the crash). A possible explanation is that analysts may view some blunt end factors as event circumstances rather thancontributing factors in themselves, and therefore do not report them. There was also an asymmetry in terms of reportedobstructions to view due to signposts and vegetation. While frequently reported as contributing for turning drivers, they wererarely reported as contributing for their counterparts in the same accidents. This probably reflects an involuntary focus of theanalyst on identifying contributing factors for the driver legally held liable, while less attention is paid to the driver judgednot at fault. Since who to blame often is irrelevant from a countermeasure development point of view, this underlyinginvestigator mindset needs addressing to avoid future bias in crash investigation reports.
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| 10. |
- Ljung Aust, Mikael, 1973, et al.
(författare)
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Fatal intersection crashes in Norway: Patterns in Contributing Factors and Data Collection Challenges
- 2012
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 45, s. 782-791
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Tidskriftsartikel (refereegranskat)abstract
- Fatal motor vehicle intersection crashes occurring in Norway in the years 2005–2007 were analyzed to identify causation patterns among their underlying contributing factors, and also to assess if the data collection and documentation procedures used by the Norwegian in-depth investigation teams produces the information necessary to do causation pattern analysis. 28 fatal accidents were analyzed. Causation charts of contributing factors were first coded for each driver in each crash using the Driving Reliability and Error Analysis Method (DREAM). Next, the charts were aggregated based on a combination of conflict types and whether the driver was going straight or turning. Analysis results indicate that drivers who were performing a turning maneuver in these crashes faced perception difficulties and unexpected behavior from the primary conflict vehicle, while at the same time trying to negotiate a demanding traffic situation. Drivers who were going straight on the other hand had less perception difficulties but largely expect anyturning drivers to yield, which led to either slow reaction or no reaction at all. In terms of common contributing factors, those often pointed to in literature as contributing to fatal crashes, e.g. high speed, drugs and/or alcohol and inadequate driver training, contributed in 12 of 28 accidents. This confirmstheir prevalence, but also shows that most drivers end up in these situations due to combinations of less auspicious contributing factors. In terms of data collection and documentation, there was an asymmetry in terms of reported obstructions to view due to signposts and vegetation. These were frequently reported as contributing for turning drivers, but rarely reported as contributing for their counterparts in the same crashes. This probably reflects an involuntary focus of the analyst on identifying contributing factors for the driver held legally liable, while less attention is paid to the driver judged not at fault. Since who toblame often is irrelevant from a countermeasure development point of view, this underlying investigator approach needs to be addressed to avoid future bias in crash investigation reports.
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