| 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)
-
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
-
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
-
Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 9
-
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)
-
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
-
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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| 11. |
- Lübbe, Nils, 1982, et al.
(författare)
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Drivers’ comfort boundaries in pedestrian crossings: A study in driver braking characteristics as a function of pedestrian walking speed
- 2015
-
Ingår i: Safety Science. - : Elsevier BV. - 0925-7535 .- 1879-1042. ; 75, s. 100-106
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Tidskriftsartikel (refereegranskat)abstract
- Systems informing or warning a driver of an imminent collision with a pedestrian or automatically initiating braking have been introduced to the car market. One of the major challenges is to balance system performance against the possibility of undesired system activation. The distinction between desired and undesired system activation can be based on driver discomfort. In this study driver discomfort can be inferred from brake onset, which refers to the start of brake pedal depression, as the most intuitive way for a driver to resolve a conflicting situation. The influences of pedestrian walking speed on brake onset and brake deceleration levels were investigated in Toyota Motor Corporation’s high-fidelity driving simulator. One hundred and eight naive volunteers drove at a target speed of 30 km/h in an urban environment and were subjected to two animations of pedestrian crossing situations projected inside the driving simulator. The pedestrian speed was 1 m/s and 2 m/s. Time To Collision (TTC) at brake onset, one of the recorded quantities, might be a suitable measure for comfort zone boundaries as it is less affected by driving speed than other measures.Pedestrian speed was found to have a statistically significant influence on brake onset. For pedestrian speeds of 1 m/s, 90% of drivers braked before 2.6 s TTC. For 2 m/s this value was 2.2 s. These values can be used to differentiate between desired and undesired system activation in the design of an "unjustified system response" test in the assessment of pedestrian safety systems.
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| 12. |
- Lübbe, Nils, 1982, et al.
(författare)
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Injury risk curves to guide safe speed limits on Swedish roads using German crash data supplemented with estimated non-injury crashes
- 2024
-
Ingår i: Accident Analysis and Prevention. - 0001-4575. ; 202
-
Tidskriftsartikel (refereegranskat)abstract
- Vision Zero postulates that no one should be killed or seriously injured in road traffic; therefore, it is necessary to define evidence-based speed limits to mitigate impact severity. The overall aims to guide the definition of safe speeds limits by establishing relations between impact speed and the risk of at-least-moderate (MAIS2+) and at-least-severe (MAIS3+) injuries for car occupants in frontal and side crashes in Sweden. As Swedish in-depth data are unavailable, the first objective was to assess the applicability of German In-depth Accident Study (GIDAS) data to Sweden. The second was to create unconditional injury risk curves (risk of injury given involvement in any crash), rather than risk curves conditional on the GIDAS sampling criterion of suspected-injury crashes. Thirdly, we compared the unconditional and conditional risk curves to quantify the practical implications of this methodological choice. Finally, we provide an example to demonstrate how injury risk curves facilitate the definition of safe, evidence-based speed limits in Sweden. Characteristics important for the injury outcome were similar between GIDAS and Swedish data; therefore, the injury risk curves using German GIDAS data are applicable to Sweden. The regression models yielded the following results for unconditional injury risk curves: 10 % MAIS2+ at 25 km/h impact speed for frontal head-on crashes, 20 km/h for frontal car-to-object crashes, 55 km/h in far-side crashes, and 45 km/h in near-side crashes. A 10 % MAIS3+ risk was reached between 70 and 75 km/h for all crash types. Conditional injury risk curves gave substantially different results; the 10 % MAIS3+ risk in near-side crashes was 140 km/h, twice the unconditional value. For example, if a 10 % MAIS3+ risk was acceptable, treating remaining uncertainty conservatively, assuming compliance with speed limits and that Automated Emergency Braking takes 20 km/h of the travel speed before impact in longitudinal traffic, the safe speed limit for car occupants on most Swedish roads would be 80 km/h and 60 km/h in intersections.
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| 13. |
- Lübbe, Nils, 1982
(författare)
-
Integrated Pedestrian Safety Assessment: A Method to Evaluate Combinations of Active and Passive Safety
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pedestrian road casualties are a major concern in many countries. Vehicle safety systems attempt to reduce casualties, and the accurate assessment of such systems is therefore essential. Passive safety assessment is well established, and additional active safety assessment has recently emerged. However, assessment methods accounting for the interaction between active and passive safety do not exist in today’s regulatory or consumer testing. An integrated safety assessment can help reduce pedestrian casualties more effectively and efficiently by taking information gained through active safety assessment into consideration and modifying the passive safety assessment accordingly.This research develops an integrated pedestrian safety assessment method and demonstrates its use in assessing combinations of passive safety and the active systems of Automated Emergency Braking (AEB) and Forward Collision Warning (FCW).Firstly, a method was developed that predicts causality costs for a vehicle using data from passive safety and AEB evaluations. Casualty costs were then compared for vehicles with good, average or poor Euro NCAP passive safety ratings in combination with an A-pillar airbag and an AEB system. The results show that the AEB system has a safety benefit broadly equivalent to increasing the Euro NCAP passive safety rating from poor to average or average to good, and that the estimated benefit of the A-pillar airbag exceeded that of the AEB system.Secondly, the method was extended to assess FCW systems. Data to model driver reactions required for the FCW assessment were obtained in a volunteer study. Applying this method for different types of FCW systems showed that such systems can, but do not necessarily, provide benefits similar to those of AEB systems. An early activating FCW system with a haptic (brake pulse) warning interface was as effective as an AEB system in reducing casualty cost.These assessments of AEB and FCW systems measure True Positive performance, which is, broadly speaking, the performance of an activated system in situations in which activation was needed. Additional False Positive requirements are proposed to ensure that active safety systems are not activated too early; a threshold of what could be considered too early was developed from the quantification of driver comfort boundaries in volunteer studies. The integrated assessment method proposed has the benefit of estimating overall safety performance with a single indicator, casualty cost, making results for different vehicles easily comparable. Furthermore, as the method aims at a realistic assessment of a vehicle’s ability to protect pedestrians, all body regions and injury severities, as well as impact kinematics, all relevant impact speeds, and their interdependencies are taken into account making this the most complete method currently developed. However, since the method relies on the testing of a vehicle’s active safety systems in representative scenarios, and on the testing of its passive safety with existing impactor tests, limitations of these existing test procedures will necessarily have an impact.It is suggested that the proposed integrated pedestrian safety method be implemented in consumer testing to assess the total benefit offered by any combination of active and passive safety technology. In addition, findings suggest that testing for active safety should be expanded to FCW systems and, furthermore, that False Positive tests should be implemented. In the test scenarios already in use for assessment of speed reductions, AEB and FCW system activation before comfort boundary timing should be discouraged. On implementing these proposals, assessment would more accurately reflect the total safety benefit offered by different systems and therefore aid the development and proliferation of the most effective and efficient pedestrian safety systems.
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| 14. |
- Lübbe, Nils, 1982
(författare)
-
Integrated pedestrian safety assessment methodology
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pedestrian fatalities and injuries are a concern in many regions. Passive safety assessment is well established, and additional active safety assessment has recently emerged. However, assessment methods reflecting on the interaction between active and passive safety do not exist in regulatory or consumer testing. An integrated safety assessment that takes consideration to the information gained by active safety evaluation and modifies the passive safety assessment accordingly is needed to reduce pedestrian casualties effectively and efficiently. Such an assessment can guide the development and proliferation of vehicles offering the greatest benefit in terms of total safety offered.The goal of this thesis is to contribute to the development of an integrated pedestrian safety assessment methodology. Firstly, conceptual work identifies key issues and a way forward for the assessment of True Positive performance, which is predicted injury reduction in test conditions in which safety systems are to be activated.Secondly, False Positive test procedures are considered to provide guidance on balancing between True Positive performance and False Positive driver annoyance (activation of automatic emergency braking or forward collision warnings in test conditions in which safety systems are not meant to activate leading to driver mistrust and switched-of systems). To do so, driver comfort zone boundaries for pedestrian crossing situations are quantified indicating the transition point from normal situations to uncomfortable driving situations in which the driver will take corrective action. This data can be used to differentiate between desired and undesired False Positive activation, which in turn can help in designing False Positive test procedures.A concept for the development of an integrated pedestrian safety assessment methodology is presented in Paper I. Further work is needed to collect data to facilitate the design of a usable and accurate assessment method from this concept.Comfort zone boundaries for pedestrian crossing situations were quantified in Papers II and III. Time-To-Collision (TTC) had comparably low variation in the driver population in two complimentary studies on both a test track and in a driving simulator. The comfort zone boundary TTC was independent of the car’s travelling speed but depended on pedestrian crossing speed. The 90 percentile value for TTC at the comfort zone boundary for 1 m/s pedestrian speed was 2.5 s in Paper II and 2.6 s in Paper III. The value for pedestrian speed of 2 m/s was 2.2 s TTC identified in Paper III.The methodology as suggested in this thesis relies on the testing of active safety systems in representative scenarios, and testing of passive safety with impactor tests. Thus, any limitations with the test procedures for active and passive safety, such as unrealistic reflectivity of test targets or lack of biofidelity of impactors, will have its impact on the integrated methodology.
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| 15. |
- Lübbe, Nils, 1982, et al.
(författare)
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Pedestrian crossing situations: Quantification of comfort boundaries to guide intervention timing
- 2014
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 71, s. 261-266
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Technical systems that warn or brake for vehicle-pedestrian encounters reduce injuries more effectively the earlier an intervention is initiated. However, premature intervention can irritate drivers, leading to system deactivation and, consequently, no injury reduction whatsoever. It has been proposed that no intervention should be initiated as long as attentive drivers are within their comfort zones. This study aims at quantifying driver comfort boundaries for pedestrian crossing situations to offer guidance for the appropriate timing of interventions. Methods: Sixty two volunteers drove through an intersection on a test track at 30 and 50 km/h. A pedestrian dummy was launched from behind an obstruction towards the driving path of the approaching car. Brake onset indicated discomfort. Time to collision (TTC), longitudinal and lateral distance were measured at brake onset. Results: TTC was independent of driving speed ranging from 2.1 to 4.3 s with a median of 3.2 s. Longitudinal distance ranged from 19 to 48 meters with an apparent difference between driving speeds. Lateral distances differed slightly, but significantly between driving speeds. The median was 3.1 m (3.2 m for 30 km/h and 2.9 m for 50 km/h) and values ranged from 1.9 to 4.1 m. Lateral distance in seconds ranged from 1.9 to 4.3 s with a median value of 3.1s (3.2 s for 30 km/h and 3.0 s for 50 km/h). Discussion: TTC was independent of driving speed, trial order and volunteer age. It might be considered suitable to intervene in situations where, for example, 90% of drivers have exceeded their comfort boundary, i.e. when drivers have already initiated braking. This percentile value translates to intervention at a TTC of 2.5 s (95% confidence 2.4-2.7 s). The study was limited to Swedish nationals, fully aware drivers, and two driving speeds, but did not investigate behavioural changes due to system interaction. Conclusion: This study showed that TTC at brake onset was a suitable measure for the quantification of driver comfort boundaries in pedestrian crossing situations. All drivers applied their brakes prior to 2.1 s TTC.
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| 16. |
- Lübbe, Nils, 1982, et al.
(författare)
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Predicted road traffic fatalities in Germany: The potential and limitations of vehicle safety technologies from passive safety to highly automated driving
- 2018
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2018-September, s. 17-52
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Konferensbidrag (refereegranskat)abstract
- It has been proposed that automated vehicles will greatly increase road traffic safety. However, few attempts have been made to quantify this thesis and to compare the expected benefits with more traditional safety systems. This study was carried out in five steps, adding systems in each step (from passive safety, standard Advances Driver Assistance Systems (ADAS), advanced ADAS, safety-minded driving, to cautious driving) in order to capture the benefit of increasing levels of automation. Conservative and optimistic rules based on the expected performance of each safety system were developed and applied to the German In-Depth Accident Study database. Adding safety systems was effective in preventing fatalities, ranging from 12-13% (step 1, passive safety, no automation, conservative-optimistic estimate) to 45-63% (step 5, cautious driving). The highest automation level, in step 5, achieved a reduction of Vulnerable Road User (VRU) fatalities of 33-41%. Thus, passive and active safety systems contribute substantially to preventing fatalities and their further development and deployment should not be abandoned. Even the safest foreseeable, highly automated passenger cars are not likely to avoid all crashes and all road traffic fatalities. While increased market penetration across safety systems will make road traffic substantially safer, more efforts are needed to protect VRUs.
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| 17. |
- Meng, Shiyang, et al.
(författare)
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Craniofacial Injuries for Helmeted and Unhelmeted Bicyclists in Germany
- 2023
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 105-112
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Konferensbidrag (refereegranskat)abstract
- Current bicycle helmet standards require impact testing mostly covering cranial or skull vault. Bicyclists are exposed to impacts to the face causing facial and basilar skull fractures, and soft tissue injuries, in addition to traumatic brain injuries. We aim to describe patterns and frequencies of craniofacial injuries grouped by anatomical and injury sites to inform new test method development in future bicycle helmet standards and subsequently promote protective designs. We analysed fully reconstructed crashes involving a bicycle from the German In-Depth Accident Study (GIDAS), crash years 2010-2022. The type and location of an injury was determined through the Abbreviated Injury Scale (2015 version), a GIDAS-own variable, and free-text information. We found that a substantial portion of craniofacial injuries were to the face for both helmeted and unhelmeted bicyclists. Facial injuries shifted from the upper face to the mid- and lower face when a helmet was worn. We identified the mid-face as the most prominent region for improving bicycle helmet safety. Hence, a new test method with an extended test area covering mid- and lower face is recommended and injury risk to commonly fractured facial bones should be assessed in future standards. Protective designs appear technically feasible: A visor in connection with a chin guard, or novel concepts using inflatable technology, can improve bicycle helmet designs for facial impact protection and could be assessed in future standards.
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| 18. |
- Meng, Shiyang, et al.
(författare)
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Evaluation of full-face, open-face, and airbag-equipped helmets for facial impact protection
- 2023
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Ingår i: Accident Analysis and Prevention. - 0001-4575. ; 191
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Two-wheeler riders frequently sustain injuries to the head and face in real-world crashes, including traumatic brain injury, basilar skull fracture, and facial fracture. Different types of helmets exist today, which are recognized as preventing head injuries in general; however, their efficacy and limitations in facial impact protection are underexplored. Biofidelic surrogate test devices and assessment criteria are lacking in current helmet standards. This study addresses these gaps by applying a new, more biofidelic test method to evaluate conventional full-face helmets and a novel airbag-equipped helmet design. Ultimately, this study aims to contribute to better helmet design and testing standards. Methods: Facial impact tests at two locations, mid-face and lower face, were conducted with a complete THOR dummy. Forces applied to the face and at the junction of the head and neck were measured. Brain strain was predicted by a finite element head model taking both linear and rotational head kinematics as input. Four helmet types were evaluated: full-face motorcycle and bike helmets, a novel design called a face airbag (an inflatable structure integrated into an open-face motorcycle helmet), and an open-face motorcycle helmet. The unpaired, two-sided student's t-test was performed between the open-face helmet and the others, which featured face-protective designs. Results: A substantial reduction in brain strain and facial forces was found with the full-face motorcycle helmet and face airbag. Upper neck tensile forces increased slightly with both full-face motorcycle (14.4%, p >.05) and bike helmets (21.7%, p =.039). The full-face bike helmet reduced the brain strain and facial forces for lower-face impacts, but not for mid-face impacts. The motorcycle helmet reduced mid-face impact forces while slightly increasing forces in the lower face. Significance of results: The chin guards of full-face helmets and the face airbag protect by reducing facial load and brain strain for lower face impact; however, the full-face helmets’ influence on neck tension and increased risk for basilar skull fracture need further investigation. The motorcycle helmet's visor re-directed mid-face impact forces to the forehead and lower face via the helmet's upper rim and chin guard: a thus-far undescribed protective mechanism. Given the significance of the visor for facial protection, an impact test procedure should be included in helmet standards, and the use of helmet visors promoted. A simplified, yet biofidelic, facial impact test method should be included in future helmet standards to ensure a minimum level of protection performance.
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| 19. |
- Mishra, Ekant, et al.
(författare)
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Assessing injury risks of reclined occupants in a frontal crash preceded by braking with varied seatbelt designs using the SAFER Human Body Model
- 2024
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Ingår i: Traffic Injury Prevention. - 1538-957X .- 1538-9588. ; 25:3, s. 445-453
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study investigated the effects of different seatbelt geometries and load-limiting levels on the kinematics and injury risks of a reclined occupant during a whole-sequence frontal crash scenario, using simulations with the Active SAFER Human Body Model (Active SHBM). Methods: The Active SHBM was positioned in a reclined position (50°) on a semi-rigid seat model. A whole-sequence frontal crash scenario, an 11 m/s2 Automated Emergency Braking (AEB) phase followed by a frontal crash at 50 km/h, was simulated. The seatbelt geometry was varied using either a B-pillar-integrated (BPI) or Belt-in-seat (BIS) design. The shoulder belt load-limiting level of the BPI seatbelt was also varied to achieve either similar shoulder belt forces (BPI_Lower_LL) or comparable upper body displacements (BPI_Higher_LL) to the BIS seatbelt. Kinematics of different body regions and seatbelt forces were compared. The risks of sustaining a mild traumatic brain injury (mTBI), two or more fractured ribs (NFR2+), and lumbar spine vertebral fractures were also compared. Results: During the pre-crash phase, head, first thoracic vertebra, and first lumbar vertebra displacements were greater with the BPI seatbelt than with the BIS, mainly due to the lack of initial contact between the torso and the seatbelt. Pelvis pre-crash displacements, however, remained consistent across seatbelt types. In the in-crash phase, variations in shoulder belt forces were directly influenced by the different load-limiting levels of the shoulder belt. The mTBI (around 20%) and NFR2+ (around 70–100%) risks were amplified with BPI seatbelts, especially at higher load-limiting force. However, the BPI design demonstrated reduced lumbar spine fracture risks (from 30% to 1%). Conclusions: The BIS seatbelt appears promising, as seen with the reduced mTBI and NFR2+ risks, for ensuring the protection of reclined occupants in frontal crashes. However, additional solutions, such as lap belt load limiting, should be considered to reduce lumbar spine loading.
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| 20. |
- Mishra, Ekant, et al.
(författare)
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Effects of Automated Emergency Braking and Seatbelt Pre-Pretensioning on Occupant Injury Risks in High-Severity Frontal Crashes
- 2022
-
Ingår i: Frontiers in Future Transportation. - : Frontiers Media SA. - 2673-5210. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- In high-severity crashes, occupant protection is challenging. Automated Emergency Braking (AEB) and seatbelt pre-pretensioning (PPT) are means to improve occupant protection; the purpose of this study was to quantify their effects on occupant injury risks in high-severity full-frontal crashes by Finite Element (FE) simulations. The SAFER Active average male Human Body Model was used as an occupant substitute. The crash pulses used were from separate full-frontal crash simulations using a Honda Accord FE model. The vehicle interior model comprised a seat, an instrument panel, a three-point pretensioned seatbelt system with a load-limiter of 3.1 kN force level, and a frontal passenger airbag. The effects of AEB and PPT were evaluated by simulating a 1 g pre-crash braking scenario for 0.5 s, with and without AEB, for three different PPT force levels: 0, 300, and 600 N. The impact speed of 80 km/h was reduced to 69 km/h by AEB. When neither system was activated, the predicted risk for an occupant to sustain two or more fractured ribs (NFR2+) was 100% for both 45- and 65-year-old male occupants. The risks were reduced when the AEB was activated, particularly for the 45-year-old occupant. When the AEB was activated, the risks of concussion and rib fractures were reduced; upper neck tension forces, pelvis Anterior Superior Iliac Spine (ASIS) forces, and lower extremity forces were also reduced. Increasing the PPT forces reduced the rib fracture risk further (to about 48% for a 45-year-old occupant with 600 N PPT force). The reduced speed due to AEB resulted in a lower concussion risk (from 71.3% to 31%). However, the concussion risk increased slightly with increased PPT forces.
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| 21. |
- Mishra, Ekant, et al.
(författare)
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Repositioning forward-leaning passengers by seatbelt pre-pretensioning
- 2023
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Ingår i: Traffic Injury Prevention. - 1538-957X .- 1538-9588. ; 24:8, s. 716-721
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The study determined the seatbelt pre-pretensioner force needed and the time required to reposition average male front-seat passengers from forward-leaning to upright using finite element simulations of the Active SAFER Human Body Model (Active SHBM). Methods: The Active SHBM was positioned in an initial forward-leaning position (29° forward from upright) on a deformable vehicle seat. A pre-pretensioner was modeled as a pre-loaded spring and its ability to reposition the forward-leaning Active SHBM to an upright position was simulated for twenty-four different pre-crash conditions. Four parameters were varied: (1) Automated Emergency Braking (AEB) active with 11 m/s2 or no AEB, (2) type of seatbelt system: Belt-In-Seat or B-pillar, (3) pre-pretensioner activation time (200 ms before, 100 ms before, or at the same time as AEB ramp-up), and (4) pre-pretensioner force (200 N, 300 N, 400 N, 600 N). The first thoracic vertebra fore-aft (T1 X) trajectories were compared against a reference upright position to determine the force and time needed to reposition and the effectiveness of repositioning in the different conditions. Results: The lowest force enabling repositioning in all simulations was 400 N (no AEB, Belt-In-Seat). It took about 350 ms. In the presence of AEB, activating the pre-pretensioner 200 ms before AEB and using 600 N pre-pretensioner force was needed for repositioning (taking 200 ms with Belt-In-Seat and 260 ms with B-pillar installations). Repositioning was faster and thus more effective with the Belt-In-Seat seatbelt in all simulations. Conclusions: All four parameters (presence of AEB, type of seatbelt system, pre-pretensioner activation time and force) affected the repositioning ability and time required. Far from all combinations repositioned a forward-leaning average male occupant model, but those found to be effective and fast appear as a feasible option for vehicle safety systems to reposition out-of-position occupants during pre-crash events.
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| 22. |
- Olleja, Pierluigi, 1995, et al.
(författare)
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Can non-crash naturalistic driving data be an alternative to crash data for use in virtual assessment of the safety performance of automated emergency braking systems?
- 2022
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Ingår i: Journal of Safety Research. - : Elsevier BV. - 0022-4375. ; 83, s. 139-151
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Developers of in-vehicle safety systems need to have data allowing them to identify traffic safety issues and to estimate the benefit of the systems in the region where it is to be used, before they are deployed on-road. Developers typically want in-depth crash data. However, such data are often not available. There is a need to identify and validate complementary data sources that can complement in-depth crash data, such as Naturalistic Driving Data (NDD). However, few crashes are found in such data. This paper investigates how rear-end crashes that are artificially generated from two different sources of non-crash NDD (highD and SHRP2) compare to rear-end in-depth crash data (GIDAS). Method: Crash characteristics and the performance of two conceptual automated emergency braking (AEB) systems were obtained through virtual simulations – simulating the time-series crash data from each data source. Results: Results show substantial differences in the estimated impact speeds between the artificially generated crashes based on both sources of NDD, and the in-depth crash data; both with and without AEB systems. Scenario types also differed substantially, where the NDD have many fewer scenarios where the following-vehicle is not following the lead vehicle, but instead catches-up at high speed. However, crashes based on NDD near-crashes show similar pre-crash criticality (time-to-collision) to in-depth crash data. Conclusions: If crashes based on near-crashes are to be used in the design and assessment of preventive safety systems, it has to be done with great care, and crashes created purely from small amounts of everyday driving NDD are not of much use in such assessment. Practical applications: Researchers and developers of in-vehicle safety systems can use the results from this study: (a) when deciding which data to use for virtual safety assessment of such systems, and (b) to understand the limitations of NDD.
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| 23. |
- Puthan Pisharam, Pradeep, 1983, et al.
(författare)
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Characterizing future crashes on Indian roads using counterfactual simulations of pre-crash vehicle safety technologies
- 2022
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Ingår i: IATSS Research. - : Elsevier BV. - 0386-1112. ; 46:4, s. 479-491
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Tidskriftsartikel (refereegranskat)abstract
- India's national road crash statistics indicate a continuing increase in casualties. Pre-crash safety technologies are effective in high-income countries, but it is unclear how these will perform in India and which crash types will remain after their implementation. The study objective was to predict and characterize the crashes resulting in moderate or more-severe injuries (Maximum Abbreviated Injury Scale 2 or above: MAIS2+) that remain on Indian roads after 22 pre-crash safety technologies have been implemented in all cars, heavy vehicles (buses and trucks), and Powered Two-Wheelers (PTW). Two deterministic rulesets (one optimistic and one conservative) were modeled for each of the pre-crash safety technologies. Each rule was designed and tuned to the functionality of one technology. The data were obtained from the Road Accident Sampling System India (RASSI) database. In addition to the effectiveness of each technology alone, the combined effectiveness of all technologies was estimated. Further, the characteristics of those crashes that none of the technologies would have avoided were determined. Rear-end-specific Autonomous Emergency Braking (AEB REAR-END) and Electronic Stability Control (ESC) installed in cars and heavy vehicles reduced MAIS2+ crashes the most. Crashes between PTWs and cars were significantly reduced by a rear-end-specific AEB installed in the cars. A pedestrian-specific AEB (AEB-PED) in cars and heavy vehicles was also shown to be effective. The only pre-crash safety technology in PTWs that was included, Antilock Braking Systems (ABS), reduced overall PTW crash involvement, but only reduced PTW-to-pedestrian crashes marginally. The largest proportion of remaining crashes were those that involved PTWs, indicating that PTW safety will remain a concern in future.
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| 24. |
- Puthan Pisharam, Pradeep, 1983, et al.
(författare)
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Defining crash configurations for Powered Two-Wheelers: Comparing ISO 13232 to recent in-depth crash data from Germany, India and China
- 2021
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 151
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Tidskriftsartikel (refereegranskat)abstract
- The motorcyclist safety standard ISO 13232, based on crash data from Europe and the USA from the 1970s, still sets the direction for the development and evaluation of protective measures today. However, it is unclear how relevant the crash configurations in the standard are to present-day motorcycle crashes in Europe, the USA and other parts of the world. We analyzed recent in-depth crash data from Germany, India and China, examining powered two-wheeler (PTW) crash configurations in which at least one police-reported serious injury was present. After assessing the relevance of the ISO's PTW crash configurations to those we found in each country, we suggested new configurations to guide the development of safety systems that would be more effective at reducing PTW-related fatalities and serious injuries. In all three databases, passenger cars were among the top two most frequent collision partners and a car front impacting the side of the PTW was the most common configuration. Notably, although collisions with trucks constituted the most common scenario in India and ground impact (primary collision) was a common scenario in both Germany and India, the ISO did not include either configuration. Further, in three of the seven ISO crash configurations, one of the collision partners is stationary, although stationary collision partners were rare in our data. Our results show that the ISO crash configurations do not represent the most frequent PTW road crashes in Germany, India or China. However, the Chinese database was confined to crashes with a collision partner with four or more wheels. Further, weighting factors for these data were not available, so we could not extrapolate the frequency of the Chinese crash configurations across the entire population. A revised version of the ISO could serve as a basis for a full-scale PTW crash test program. However, the observed differences between countries imply that a single global standard may not be feasible. To optimize the evaluation of a PTW safety system, we recommend the inclusion of configurations which are frequent in the region or country of interest—in addition to common configurations occurring frequently all around the world.
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| 25. |
- Ranmal, Aarti, et al.
(författare)
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Rib and sternum fracture risks for restrained occupants in frontal car crashes
- 2024
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Ingår i: Traffic Injury Prevention. - 1538-957X .- 1538-9588. ; 25:4, s. 616-622
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Tidskriftsartikel (refereegranskat)abstract
- Objective Most car occupant fatalities occur in frontal crashes and the thorax is the most frequently injured body region. The objectives of the study were, firstly, to quantify the relation between risk factors (such as speed and occupant age) and rib and sternum fracture injury probability in frontal car crashes, and, secondly, to evaluate whether rib fracture occurrence can predict sternum fractures. Methods Weighted German data from 1999-2021 were used to create the injury risk curves to predict both, at least moderate and at least serious, rib and sternum fracture risks. A contingency table for rib and sternum fractures allowed the calculation of sensitivity, specificity, and precision, as well as testing for the association. Results Elderly occupants (>= 65 years old) had increased rib and sternum fracture risk compared to mid aged occupants (18-64 years old). Besides occupant age, delta-V was always and sex sometimes a significant predictor for skeletal thoracic injury. Sternum fractures were more common than rib fractures and more likely to occur at any given delta-V. Sternum fractures occurred often in isolation. Female occupants were at higher risk than males to sustain at least moderate rib and sternum fractures together and sternum fractures in isolation. Rib and sternum fractures were associated, but low sensitivity and precision show that rib fractures do not predict sternum fractures well. Conclusions Elderly and female occupants were at the highest risk and should be targeted by thoracic injury criteria and thresholds for frontal crash occupant protection. Rib and sternum fractures were not associated. Therefore, sternum fractures need to be predicted and evaluated separately from rib fractures.
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| 26. |
- Rizzi, Matteo, 1979, et al.
(författare)
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PROPOSED SPEED LIMITS FOR THE 2030 MOTOR VEHICLE
- 2023
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Ingår i: 27th ESV Conference Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Vision Zero builds on the aspiration to keep kinetic energy below human tolerance to prevent fatalities and serious injuries. In this work, a Swedish expert group within the SAFER arena estimated the maximum safe speed limits for the 2030 motor vehicle based on the boundary conditions of vehicles, road infrastructure and human crash tolerance to achieve close to zero road fatalities and serious injuries. The present work was based on expert consensus, rather than a retrospective quantitative analysis of crash data. Different load cases were discussed separately, with the involvement of a passenger car being the common denominator. The passenger car and its collision partner were assumed to be of model year 2030, thus reflecting the base safety level of the Swedish car fleet by approximately 2050. The boundary conditions were set based on pre-crash autonomous braking ability and the maximum acceptable impact speeds that would result in a very low risk of death or serious injury among the car occupants and the car’s collision partner. In the case of car to pedestrian impacts, the acceptable impact speed was set to zero, as any impact with pedestrians can lead to serious injuries as a result of ground impacts. It was expected that the responsibility to comply with speed limits will move from the driver to the car itself, and that travel speeds will be autonomously reduced when low road friction, sight obstructions, and other challenges in the traffic environment are detected. This function was expected to be non-overridable. Lateral control was also expected to be further enhanced with lane support technologies, although it was assumed that it will be still possible to override such technologies. Over time, increased performance of vehicle safety technologies will likely be able to prevent an increasingly large proportion of crashes in all load cases. However, in line with Vision Zero design principles, human crash tolerance will always be the ultimate boundary condition to guarantee a safe outcome in a crash. As a result, the recommended maximum travel speeds in the road transport system containing motor vehicles only of model year 2030 and beyond are: Rizzi 1 5-7 km/h in pedestrian priority areas, 40 km/h in mixed traffic urban areas, if there are no obstructed sensor sightlines, e.g. due to parked vehicles along the sidewalk, 50 to 80 km/h on roads without mid- and roadside barriers, 100+ km/h on roads with continuous mid- and roadside barriers, 40 to 60 km/h in intersections, depending on vehicle mass differences. The results from this work can be used to inform the development and amendment of transport planning guidelines when moving away from the economical paradigm into Safe System boundary conditions in the setting of speed limits.
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| 27. |
- Sander, Ulrich, 1971, et al.
(författare)
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Market penetration of intersection AEB: Characterizing avoided and residual straight crossing path accidents
- 2018
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 115:June 2018, s. 178-188
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Tidskriftsartikel (refereegranskat)abstract
- Car occupants account for one third of all junction fatalities in the European Union. Driver warning can reduce intersection accidents by up to 50 percent; adding Autonomous Emergency Braking (AEB) delivers a reduction of up to 70 percent. However, these findings are based on an assumed 100 percent equipment rate, which may take decades to achieve. Our study investigates the relationship between intersection AEB market penetration rates and avoidance of accidents and injuries in order to guide implementation strategies. Additionally, residual accident characteristics (impact configurations and severity) are analyzed to provide a basis for future in-crash protection requirements. We determined which accidents would have been avoided through the use of an Intersection AEB system with different sensor field-of-view (180°) by means of re-simulating the pre-crash phase of 792 straight crossing path (SCP) car-to-car accidents recorded in the German In-Depth Accident Study (GIDAS) and the associated Pre-Crash Matrix (PCM). Intersection AEB was activated when neither of the conflict opponents could avoid the crash through reasonable braking or steering reactions. For not-avoided accidents, we used the Kudlich-Slibar rigid body impulse model to calculate the change of velocity during the impact as a measure of impact severity and the principal direction of force. Accident avoidance over market penetration is not linear but exponential, with higher gains at low penetration rates and lower gains at higher rates. A wide field-of-view sensor (180°) substantially increased accident avoidance and injury mitigation rates compared to a 120° field-of-view sensor. For a 180° field-of-view sensor at 100 percent market penetration, about 80 percent of the accidents and 90 percent of the MAIS2+F injuries could be avoided. For the remaining accidents, AEB intervention rarely affected side of impact. The median change of velocity (delta-V) of the remaining crashes reduces only marginally at low penetration rates but this reduction increases with higher penetration rates. With 100 percent market penetration, one quarter of the vehicles still involved in straight crossing path accidents will sustain a delta-V higher than 17 km/h. Intersection AEB is very effective. Enabling a fast initial implementation of systems with wide field-of-view sensor(s) and ensuring a high market penetration over the longer term is essential to achieve high crash avoidance and injury mitigation rates over time. The standards for in-crash protection must be high to mitigate injury in the unavoidable, residual accidents.
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| 28. |
- Sander, Ulrich, 1971, et al.
(författare)
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Prediction of Accident Evolution by Diversification of Influence Factors in Computer Simulation: Opportunities for Driver Warnings in Intersection Accidents
- 2016
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Ingår i: Methodenentwicklung für Aktive Sicherheit und Automatisiertes Fahren. - 9783816933656 ; 2016, s. 13-41
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Konferensbidrag (refereegranskat)abstract
- Single Accident Reconstructions and Traffic Simulation have both been frequently utilizedfor prospective assessment of advanced driver assistance and active safety systems. Whereas Single Accident Reconstructions cannot estimate False Positive rates due to the limitation to accidents and hence to True Positives and True Negatives, Traffic Simulation is prone to neglecting rare surprise events that are important for system performance. Further, a False Positive intervention does not necessarily imply driver non-acceptance.Driver comfort boundaries seem to be a more eligible metric for intervention acceptance. Intersection accidents are frequent and harmful. In the US, about 50% of all crashes with injuries are located in intersections or are intersection related. Approximately one third ofall fatal crashes occur at these locations. About 24% of the road traffic fatalities in Europe are attributed to junction accidents. For Germany, straight crossing path accidents (SCP) and left turn across path accidents with traffic in opposite direction (LTAP/OD) are the most frequent intersection conflict types, covering one quarter of all car-to-car accidents.The objective of this study was the application of Single Accident Reconstruction data to virtual simulation to quantify the time available between comfort zone boundaries and physical limits for collision avoidance in the intersection scenarios SCP and LTAP/OD. Thus, the question is answered, if warning is an appropriate measure for intersection accident avoidance. We investigated different warning levels comprising the ego and target vehicle drivers’ alternatives to avoid impending collisions by either braking or steering within comfort margins and a range of warning thresholds at 3m/s^2 , 5m/s^2 , and7m/s^2 longitudinal and lateral acceleration.The results show that the available time is limited with 0.6 to 0.7 seconds (SCP) and 0.2 to 0.6 seconds (LTAP/OD) for the lowest warning level and a threshold of 3m/s 2longitudinal and lateral acceleration. For higher warning levels and thresholds, available times decreased substantially. Negative times occurred in LTAP/OD scenarios when braking was considered on its own as a warning intervention decision, indicating that forsome accidents comfort braking can be initiated later than braking at the physical limit.
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| 29. |
- Sander, Ulrich, 1971, et al.
(författare)
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The potential of clustering methods to define intersection test scenarios: Assessing real-life performance of AEB
- 2018
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 113, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Intersection accidents are frequent and harmful. The accident types ‘straight crossing path’ (SCP), ‘left turn across path – oncoming direction’ (LTAP/OD), and ‘left-turn across path – lateral direction’ (LTAP/LD) represent around 95% of all intersection accidents and one-third of all police-reported car-to-car accidents in Germany. The European New Car Assessment Program (Euro NCAP) have announced that intersection scenarios will be included in their rating from 2020; however, how these scenarios are to be tested has not been defined. This study investigates whether clustering methods can be used to identify a small number of test scenarios sufficiently representative of the accident dataset to evaluate Intersection Automated Emergency Braking (AEB). Data from the German In-Depth Accident Study (GIDAS) and the GIDAS-based Pre-Crash Matrix (PCM) from 1999 to 2016, containing 784 SCP and 453 LTAP/OD accidents, were analyzed with principal component methods to identify variables that account for the relevant total variances of the sample. Three different methods for data clustering were applied to each of the accident types, two similarity-based approaches, namely Hierarchical Clustering (HC) and Partitioning Around Medoids (PAM), and the probability-based Latent Class Clustering (LCC). The optimum number of clusters was derived for HC and PAM with the silhouette method. The PAM algorithm was both initiated with random start medoid selection and medoids from HC. For LCC, the Bayesian Information Criterion (BIC) was used to determine the optimal number of clusters. Test scenarios were defined from optimal cluster medoids weighted by their real-life representation in GIDAS. The set of variables for clustering was further varied to investigate the influence of variable type and character. We quantified how accurately each cluster variation represents real-life AEB performance using pre-crash simulations with PCM data and a generic algorithm for AEB intervention. The usage of different sets of clustering variables resulted in substantially different numbers of clusters. The stability of the resulting clusters increased with prioritization of categorical over continuous variables. For each different set of cluster variables, a strong in-cluster variance of avoided versus non-avoided accidents for the specified Intersection AEB was present. The medoids did not predict the most common Intersection AEB behavior in each cluster. Despite thorough analysis using various cluster methods and variable sets, it was impossible to reduce the diversity of intersection accidents into a set of test scenarios without compromising the ability to predict real-life performance of Intersection AEB. Although this does not imply that other methods cannot succeed, it was observed that small changes in the definition of a scenario resulted in a different avoidance outcome. Therefore, we suggest using limited physical testing to validate more extensive virtual simulations to evaluate vehicle safety.
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| 30. |
- Sui, Bo, 1987, et al.
(författare)
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A clustering approach to developing car-to-two-wheeler test scenarios for the assessment of Automated Emergency Braking in China using in-depth Chinese crash data
- 2019
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 132
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Tidskriftsartikel (refereegranskat)abstract
- Two-wheeled vehicles (motorized and non-motorized, referred to as TWs) are an important part of the transport system in China. They also represent an important challenge for road safety, with many TW user fatalities and injuries every year. Recently, active safety systems for cars, such as Automated Emergency Braking (AEB), promise to reduce road traffic fatalities and injuries. For these systems to work effectively, it is necessary to understand and define the complex traffic scenarios to be addressed. The aim of this study is to contribute to the development of test procedures for AEB specifically, drawing on the China In-Depth Accident Study (CIDAS) data from July 2011 to February 2016 to describe typical scenarios for crashes between cars and TWs by means of cluster analysis. In total, 672 car-to-TW crashes were extracted. The data was clustered according to five main crash characteristics: time of crash, view obstruction, pre-crash driving behavior of the car driver and the TW driver, and relative moving direction. The analysis resulted in six car-to-TW crash scenarios typical of China. In three scenarios the car and the TW travel perpendicularly to each other before the crash, in two they travel in the same direction, and in one they travel in opposite directions. Further, each scenario can be described with three characteristics (the road speed limit, the TW's first contact point on the car, and the car's first contact point on the TW) that can be included in an AEB test suite. Some scenarios were similar to those in the Euro New Car Assessment Program (Euro NCAP). For example, in one, a TW moving straight ahead was hit by a car moving perpendicularly, and in the other the car hit a TW traveling in the same direction. Both occurred in daytime, without a visual obstruction. However, in contrast to the Euro NCAP, typical scenarios in China included night-time scenarios, scenarios where the car or the TW was turning, and those in which the TW was hidden from the car by an obstruction. The results contribute to a proposed novel AEB test suite with realistic scenarios specific to China.
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| 31. |
- Sui, Bo, et al.
(författare)
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Evaluating automated emergency braking performance in simulated car-to-two-wheeler crashes in China: A comparison between C-NCAP tests and in-depth crash data
- 2021
-
Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 159
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Tidskriftsartikel (refereegranskat)abstract
- Automated Emergency Braking (AEB) is an effective way to prevent crashes from happening or mitigate their severity. Because riders of two-wheelers (TWs) are among the most vulnerable road users, New Car Assessment Programs, like the China New Car Assessment Program (C-NCAP), have recently introduced test scenarios for the assessment of AEB for cars encountering TWs (TW-AEB). The main aim of this study was to determine how well two different C-NCAP test scenario datasets reflect real-world crash scenarios for the purpose of assessing TW-AEB performance. We used virtual counterfactual simulations to determine whether the hypothetical TW-AEB's performance, when applied to the two C-NCAP datasets, was similar to its performance when applied to a set of reconstructed car-to-TW crashes representing real-world crashes. The test datasets were the current C-NCAP scenario set and a proposed C-NCAP scenario set; the real-world crash dataset comprised 113 reconstructed crashes from the Shanghai United Road Traffic Safety Scientific Research Center database (SHUFO). The performances were compared with respect to crash avoidance rate and the characteristics of the remaining crashes. A substantially higher proportion of crashes was avoided in the current C-NCAP scenario set than in the other two (with the sensor field of view (FoV) set to 70° and the activation time to 1.1 s TTC). In fact, with these parameter settings, no crashes remained in the current C-NCAP scenarios, while only 37% and 46% of the crashes in the proposed C-NCAP scenario set and SHUFO crash set were avoided, respectively. Our findings show that TW-AEB systems which are optimized for the current C-NCAP test scenarios are likely to provide benefits in real-world crashes. However, including additional test scenarios which reflect real-world crash situations more accurately would likely lead to a higher correlation between C-NCAP scores and real-world TW-AEB performance. In particular, we recommend the introduction of longitudinal same-direction scenarios with the car or TW turning and perpendicular scenarios with high TW traveling speed, in future C-NCAP releases. Inclusion of these scenarios in C-NCAP might reward improvements of future TW-AEBs toward systems that can save more lives. Furthermore, our study shows that there is likely to be a substantial number of crashes with an impact speed higher than 40 km/h still remaining even after the widespread application of TW-AEB. Therefore, passive safety for TW riders on Chinese roads will be still needed.
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| 32. |
- Svenning, Erik, 1986, et al.
(författare)
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Comparing the Frontal Impact Responses of the VIVA+ Average Female and SAFER Average Male Human Body Models in a Generic Seat
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The VIVA+ 50F average female Human Body Model (HBM), currently in early beta status, was compared to the SAFER average male HBM Version 9 with the aim of investigating differences between females and males in terms of kinematics and injury assessment in frontal impacts. The VIVA+ HBM is under development within the research project VIRTUAL and will be released as open source during the summer 2022. The comparison between the HBMs was carried out using LS-DYNA version R9.3.1 in a generic sled test interior consisting of a semi-rigid seat, a footwell and a pretensioned three-point belt system with 3.5 kN load limiter. The HBMs were positioned in a pre-simulation using spring and damper elements attached to target points estimated using an automobile driving posture prediction model from the literature. Subsequently, the HBMs were subjected to a frontal crash corresponding to an initial velocity of 50 km/h. Occupant kinematics were analyzed by comparing head, chest, and pelvis kinematics between the two models. Additionally, HIC15, rib peak strains, and upper neck, lumbar spine and pelvis anterior superior iliac spine (ASIS) resultant forces were compared between the two models. The largest differences between SAFER HBM and the beta version of VIVA+ were found for rib peak strains, where VIVA+ predicts higher strain than SAFER HBM, and lumbar spine forces, where VIVA+ predicts lower forces than SAFER HBM. Furthermore, higher neck forces and ASIS forces were predicted by SAFER HBM compared to VIVA+.
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