| 1. |
- Dozza, Marco, 1978, et al.
(författare)
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How do drivers negotiate intersections with pedestrians? Fractional factorial design in an open-source driving simulator
- 2017
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Ingår i: Proceeding of the Road Safety and Simulation International Conference, RSS2017, 17-19 October 2017.
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Konferensbidrag (refereegranskat)abstract
- Forward collision warning (FCW) and autonomous emergency braking (AEB) systems are increasingly available and promise to prevent or mitigate collisions by alerting the driver or autonomously braking the vehicle. Threat-assessment and decision-making algorithms for FCW and AEB aim to find the best compromise for safety by intervening at the “right” time: neither too early, potentially upsetting the driver, nor too late, possibly missing opportunities to avoid the collision.Today, the extent to which intervention times for FCW and AEB should depend on factors such as pedestrian speed and lane width is unknown. To guide the design of FCW and AEB intervention time, we employed a fractional factorial design, and determined how seven factors (crossing side, car speed, pedestrian speed, crossing angle, pedestrian size, zebra presence, and lane width) affect the driver’s response process and comfort zone when negotiating an intersection with a pedestrian. Ninety-four volunteers drove through an intersection in a fixed-base driving simulator, which was based on open-source software (OpenDS). Several parameters, including pedestrian time-to-arrival and driver response time, were calculated to describe the driver response process and define driver comfort boundaries.Linear mixed-effect models showed that driver responses depended mainly on pedestrian time-to-arrival and visibility, whereas factors such as pedestrian size, zebra presence, and lane width did not significantly influence the driver response process. Some drivers changed their negotiation strategy to minimize driving effort over the course of the experiment. Experienced drivers changed more than less experienced drivers; nevertheless, all drivers behaved similarly, independent of driving experience. The flexible and customizable driving environment provided by OpenDS proved to be a viable solution for behavioural experiments in driving simulators.Results from this study suggest that visibility and pedestrian time-to-arrival are the most important factors for defining the earliest acceptable FCW and AEB activations. Fractional factorial design effectively compared the influence of several factors on driver behaviour within a single experiment; however, this design did not allow in-depth data analysis. In the future, OpenDS may became a standard platform, enabling crowdsourcing and favouring repeatability across studies in traffic safety. Finally, this study may guide future design and evaluation of FCW and AEB by highlighting which factors deserve further investigation and which ones do not.
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| 2. |
- Dozza, Marco, 1978, et al.
(författare)
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How do drivers negotiate intersections with pedestrians? The importance of pedestrian time-to-arrival and visibility
- 2020
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 105524:June 2020
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Tidskriftsartikel (refereegranskat)abstract
- Forward collision warning (FCW) and autonomous emergency braking (AEB) systems are increasingly available and prevent or mitigate collisions by alerting the driver or autonomously braking the vehicle. Threat-assessment and decision-making algorithms for FCW and AEB aim to find the best compromise for safety by intervening at the “right” time: neither too early, potentially upsetting the driver, nor too late, possibly missing opportunities to avoid the collision. Today, the extent to which activation times for FCW and AEB should depend on factors such as pedestrian speed and lane width is unknown. To guide the design of FCW and AEB intervention time, we employed a fractional factorial design, and determined how seven factors (crossing side, car speed, pedestrian speed, crossing angle, pedestrian size, zebra-crossing presence, and lane width) affect the driver’s response process and comfort zone when negotiating an intersection with a pedestrian. Ninety-four volunteers drove through an intersection in a fixed-base driving simulator, which was based on open-source software (OpenDS). Several parameters, including pedestrian time-to-arrival and driver response time, were calculated to describe the driver response process and define driver comfort boundaries. Linear mixed-effect models showed that driver responses depended mainly on pedestrian time-to-arrival and visibility, whereas factors such as pedestrian size, zebra-crossing presence, and lane width did not significantly influence the driver response process. Some drivers changed their negotiation strategy (proportion of pedal braking to engine braking) to minimize driving effort over the course of the experiment. Experienced drivers changed more than less experienced drivers; nevertheless, all drivers behaved similarly, independent of driving experience. The flexible and customizable driving environment provided by OpenDS may be a viable platform for behavioural experiments in driving simulators. Results from this study suggest that visibility and pedestrian time-to-arrival are the most important variables for defining the earliest acceptable FCW and AEB activations. Fractional factorial design effectively compared the influence of several factors on driver behaviour within a single experiment; however, this design did not allow in-depth data analysis. In the future, OpenDS might become a standard platform, enabling crowdsourcing and favouring repeatability across studies in traffic safety. Finally, this study advises future design and evaluation procedures (e.g. new car assessment programs) for FCW and AEB by highlighting which factors deserve further investigation and which ones do not.
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| 3. |
- Åkerberg Boda, Christian-Nils, 1989, et al.
(författare)
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Modelling discomfort: How do drivers feel when cyclists cross their path?
- 2020
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 146
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Even as worldwide interest in bicycling continues to grow, cyclists constitute a large part of road fatalities. A major part of the fatalities occurs when cyclists cross a vehicle path. Active safety systems and automated driving systems may already account for these interactions in their control algorithms. However, the driver behaviour models that these systems use may not be optimal in terms of driver acceptance. If the systems could estimate driver discomfort, their acceptance might be improved. Method: This study investigated the degree of discomfort experienced by drivers when cyclists crossed their travel path. Participants were instructed to drive through an intersection in a fixed-base simulator or on a test track, following the same experimental protocol. The effects of demographic variables (age, gender, driving frequency, and yearly mileage), controlled variables (car speed, bicycle speed, and bicycle-car configuration), and a visual cue (car’s time-to-arrival at the intersection when the bicycle appears; TTAvis) on self-reported discomfort were analysed using cumulative link mixed models (CLMM). Results: Results showed that demographic variables had a significant effect on the discomfort felt by drivers—and could explain the variability observed between drivers. Across both experimental environments, the controlled variables were shown to significantly influence discomfort. TTAvis was shown to have a significant effect on discomfort as well; the closer to zero TTAvis was (i.e., the more critical the situation), the more likely the driver red great discomfort. The prediction accuracies of the CLMM with controlled variables and the CLMM with the visual cue were similar, with an average accuracy between 40 and 50%. Surprise trials in the simulator experiment, in which the bicycle appeared unexpectedly, improved the prediction accuracy of the models, more notably the CLMM including TTAvis. Conclusions: The results suggest that the discomfort was mainly driven by the visual cue rather than the deceleration cues. Thus, it is suggested that an algorithm that estimates driver discomfort be included in active safety systems and autonomous driving systems. The CLMM including TTAvis was presented as a potential candidate to serve this purpose.
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| 4. |
- Åkerberg Boda, Christian-Nils, 1989, et al.
(författare)
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Modelling how drivers respond to a bicyclist crossing their path at an intersection: How do test track and driving simulator compare?
- 2018
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 111, s. 238-250
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Tidskriftsartikel (refereegranskat)abstract
- Bicyclist fatalities are a great concern in the European Union. Most of them are due to crashes between motorized vehicles and bicyclists at unsignalised intersections. Different countermeasures are currently being developed and implemented in order to save lives. One type of countermeasure, active safety systems, requires a deep understanding of driver behaviour to be effective without being annoying. The current study provides new knowledge about driver behaviour which can inform assessment programmes for active safety systems such as Euro NCAP. This study investigated how drivers responded to bicyclists crossing their path at an intersection. The influences of car speed and cyclist speed on the driver response process were assessed for three different crossing configurations. The same experimental protocol was tested in a fixed-base driving simulator and on a test track. A virtual model of the test track was used in the driving simulator to keep the protocol as consistent as possible across testing environments. Results show that neither car speed nor bicycle speed directly influenced the response process. The crossing configuration did not directly influence the braking response process either, but it did influence the strategy chosen by the drivers to approach the intersection. The point in time when the bicycle became visible (which depended on the car speed, the bicycle speed, and the crossing configuration) and the crossing configuration alone had the largest effects on the driver response process. Dissimilarities between test-track and driving-simulator studies were found; however, there were also interesting similarities, especially in relation to the driver braking behaviour. Drivers followed the same strategy to initiate braking, independent of the test environment. On the other hand, the test environment affected participants' strategies for releasing the gas pedal and regulating deceleration. Finally, a mathematical model, based on both experiments, is proposed to characterize driver braking behaviour in response to bicyclists crossing at intersections. This model has direct implications on what variables an in-vehicle safety system should consider and how tests in evaluation programs should be designed.
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| 5. |
- Batkovic, Ivo, 1992, et al.
(författare)
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A Computationally Efficient Model for Pedestrian Motion Prediction
- 2018
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Konferensbidrag (refereegranskat)abstract
- We present a mathematical model to predict pedestrian motion over a finite horizon, intended for use in collision avoidance algorithms for autonomous driving. The model is based on a road map structure, and assumes a rational pedestrian behavior. We compare our model with the state-of-the art and discuss its accuracy, and limitations, both in simulations and in comparison to real data.
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| 6. |
- Dean, Morgan E., et al.
(författare)
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Assessing the applicability of impact speed injury risk curves based on US data to defining safe speeds in the US and Sweden
- 2023
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Ingår i: Accident Analysis and Prevention. - 0001-4575. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Vision Zero is an approach to road safety that aims to eliminate all traffic-induced fatalities and lifelong injuries. To reach this goal, a multi-faceted safe system approach must be implemented to anticipate and minimize the risk associated with human mistakes. One aspect of a safe system is choosing speed limits that keep occupants within human biomechanical limits in a crash scenario. The objective of this study was to relate impact speed and maximum delta-v to risk of passenger vehicle (passenger cars and light trucks and vans) occupants sustaining a moderate to fatal injury (MAIS2+F) in three crash modes: head-on vehicle-vehicle, frontal vehicle–barrier, and front-to-side vehicle-vehicle crashes. Data was extracted from the Crash Investigation Sampling System, and logistic regression was used to construct the injury prediction models. Impact speed was a statistically significant predictor in head-on crashes, but was not a statistically significant predictor in vehicle-barrier or front–to–side crashes. Maximum delta-v was a statistically significant predictor in all three crash modes. A head-on impact speed of 62 km/h yielded 50% (±27%) risk of moderate to fatal injury for occupants at least 65 years old. A head-on impact speed of 82 km/h yielded 50% (±31%) risk of moderate to fatal injury for occupants younger than 65 years. Compared to the impact speeds, the maximum delta-v values yielding the same level of risk were lower within the head-on crash population. A head-on delta-v of 40 km/h yielded 50% (±21%) risk of moderate to fatal injury for occupants at least 65 years old. A head-on delta-v of 65 km/h yielded 50% (±33%) risk of moderate to fatal injury for occupants younger than 65 years. A maximum delta–v value of approximately 30 km/h yielded 50% (±42%) risk of MAIS2+F injury for passenger car occupants in vehicle-vehicle front-to-side crashes. A maximum delta–v value of approximately 44 km/h yielded 50% (±24%) risk of MAIS2+F injury for light truck and van occupants, respectively, in vehicle-vehicle front-to-side crashes.
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| 7. |
- Jonsson, Jonathan, 1989, et al.
(författare)
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The Effect of Advanced Automatic Collision Notification (AACN) on Road Fatality Reduction in Sweden
- 2015
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Ingår i: Proceedings of the 3rd International Symposium on Future Active Safety Technology Towards Zero Traffic Accidents (FAST-zero 2015).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper aims at estimating the effect of the Advanced Automatic Collision Notification (AACN) post–crash system on road fatality reduction in Sweden. The analysis was based on the Swedish Traffic Accident Data Acquisition (STRADA) database in combination with in-depth studies of fatal accidents. Logistic regression with backward selection was used to identify relevant variables and develop a statistical model. The variables ‘admission to trauma center’, ‘age’ and ‘injury severity’ were identified as significant and by applying the final model on fatalities in passenger cars the estimated fatality reduction due to AACN was calculated. AACN was estimated to potentially reduce road fatalities by 9.6% (95% CI = -0.1-18.4%)
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| 8. |
- Kovaceva, Jordanka, 1980, et al.
(författare)
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A new framework for modelling road-user interaction and evaluating active safety systems
- 2018
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Ingår i: 7th International Cycling Safety Conference 2018.
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Konferensbidrag (refereegranskat)abstract
- In the road transport system, cyclists account for a significant share of fatalities and serious injuries. Advance driver assistance systems (ADAS) that address potential crashes of passenger cars with cyclists are being developed and introduced to the market. Safety benefit evaluation of these ADAS is important to verify if current ADAS actually reduce real-world crashes and to determine the extent to which novel algorithms may improve current ADAS, before entering the market. ADAS safety benefit evaluation requires an agreed framework with defined concepts for target scenario specification, models of road‑user behaviour and road‑user interaction, and performance metrics.
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| 9. |
- Larsson, Karl-Johan, 1985, et al.
(författare)
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Rib Cortical Bone Fracture Risk as a Function of Age and Rib Strain: Updated Injury Prediction Using Finite Element Human Body Models
- 2021
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate vehicle occupant injury risk, finite element human body models (HBMs) can be used in vehicle crash simulations. HBMs can predict tissue loading levels, and the risk for fracture can be estimated based on a tissue-based risk curve. A probabilistic framework utilizing an age-adjusted rib strain-based risk function was proposed in 2012. However, the risk function was based on tests from only twelve human subjects. Further, the age adjustment was based on previous literature postulating a 5.1% decrease in failure strain for femur bone material per decade of aging. The primary aim of this study was to develop a new strain-based rib fracture risk function using material test data spanning a wide range of ages. A second aim was to update the probabilistic framework with the new risk function and compare the probabilistic risk predictions from HBM simulations to both previous HBM probabilistic risk predictions and to approximate real-world rib fracture outcomes. Tensile test data of human rib cortical bone from 58 individuals spanning 17–99 years of ages was used. Survival analysis with accelerated failure time was used to model the failure strain and age-dependent decrease for the tissue-based risk function. Stochastic HBM simulations with varied impact conditions and restraint system settings were performed and probabilistic rib fracture risks were calculated. In the resulting fracture risk function, sex was not a significant covariate—but a stronger age-dependent decrease than previously assumed for human rib cortical bone was evident, corresponding to a 12% decrease in failure strain per decade of aging. The main effect of this difference is a lowered risk prediction for younger individuals than that predicted in previous risk functions. For the stochastic analysis, the previous risk curve overestimated the approximate real-world rib fracture risk for 30-year-old occupants; the new risk function reduces the overestimation. Moreover, the new function can be used as a direct replacement of the previous one within the 2012 probabilistic framework.
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| 10. |
- Lübbe, Nils, 1982, et al.
(författare)
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Assessment of Integrated Pedestrian Protection Systems with Forward Collision Warning and Automated Emergency Braking
- 2015
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Ingår i: 2015 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury. ; , s. 385-397
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Konferensbidrag (refereegranskat)abstract
- Automated Emergency Braking systems reduce impact speeds, and consequently, injuries in car‐ to‐pedestrian impacts. The development of assessment methods for these systems has received considerable attention. Forward Collision Warning systems similarly aim at reducing impact speed, but have received less attention. Casualty cost reductions of several simplified but realistic Forward Collision Warning and Automated Emergency Braking systems were calculated using simulations and a modified AsPeCSS method. Automated Emergency Braking systems were assessed to result in approximately 25% casualty cost reductions. Forward Collision Warning effectiveness ranged from “no benefit” for an audio‐visual warning system with late activation, to a benefit of 25 % casualty cost reduction for an early activating warning system including an additional short brake pulse. As Forward Collision Warning seems to have the potential to reduce pedestrian casualties of the same magnitude as Automated Emergency Braking, the authors suggest including a Forward Collision Warning assessment in a modified AsPeCSS method to rate pedestrian protection of cars.
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