| 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. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Nilsson, Emma, 1982, et al.
(författare)
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Effects of cognitive load on response time in an unexpected lead vehicle braking scenario and the detection response task (DRT)
- 2018
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Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478. ; 59, s. 463-474
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Tidskriftsartikel (refereegranskat)abstract
- The effects of cognitive distraction on traffic safety and driver performance are unclear and under debate. Based on increased response times to stimuli or events in controlled driving experiments, concerns, primarily about cell phone usage during driving, have been raised. But while cognitive load repeatedly have been shown to increase response times in artificial tasks such as the Detection Response Task (DRT), the generalizability of the results to response times in critical traffic situations is questionable. Method: Two experiments were conducted. In Experiment 1, response times in the DRT were measured during simulated driving with and without execution of a cognitively loading secondary task. In Experiment 2, brake response times in an unexpected lead vehicle braking scenario were measured with and without the same cognitively loading task. Results: In Experiment 1, DRT response times increased with increased level of cognitive load. In Experiment 2, brake response times were unaffected by cognitive load. Conclusion: The response time results from the artificial DRT did not generalize to the critical lead vehicle braking scenario. This finding can possibly be explained by the cognitive control hypothesis, which suggests that cognitive load selectively impairs driving subtasks that rely on cognitive control (i.e. novel or inconsistent tasks) but leaves automatic performance unaffected (Engström, Markkula, Victor, & Merat, 2017). While the DRT responses, because of the task novelty, can be assumed to require cognitive control, responses to visually expanding objects, such as a braking lead vehicle with short time headway, are triggered automatically. Common interpretations of the effect of cognitive load on traffic safety thus need to be re-examined. It seems inappropriate to generalize from effects of cognitive load on DRT, or other artificial laboratory tasks that rely on cognitive control, to unexpected real-world situations where responses are triggered primarily by looming cues.
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| 7. |
- WALLÉN WARNER, HENRIETTE, 1972, et al.
(författare)
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Dream 3.0. Documentation of references supporting the links in the classification scheme
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Both the Driving Reliability and Error Analysis Method (DREAM; Ljung, 2002) and theSafetyNet Accident Causation System (SNACS; Ljung, 2006) have been successfully used astools for accident analysis in Sweden as well as in other European countries. While the drivervehicle/traffic environment-organisation triad are used as frames of reference and theContextual Control Model (COCOM; Hollnagel, 1998) is used to organise human cognition,the links in the classification schemes have not been established by referring to literature. Theaim of this literature review is therefore to investigate the empirical support for the links inthe classification scheme of DREAM 3.0 (an updated version of DREAM/SNACS).
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