Assessing the applicability of impact speed injury risk curves based on US data to defining safe speeds in the US and Sweden.

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.

European NCAP Program Developments to Address Driver Distraction, Drowsiness and Sudden Sickness.

Driver distraction and drowsiness remain significant contributors to death and serious injury on our roads and are long standing issues in road safety strategies around the world. With developments in automotive technology, including driver monitoring, there are now more options available for automotive manufactures to mitigate risks associated with driver state. Such developments in Occupant Status Monitoring (OSM) are being incorporated into the European New Car Assessment Programme (Euro NCAP) Safety Assist protocols. The requirements for OSM technologies are discussed along two dimensions: detection difficulty and behavioral complexity. More capable solutions will be able to provide higher levels of system availability, being the proportion of time a system could provide protection to the driver, and will be able to capture a greater proportion of complex real-word driver behavior. The testing approach could initially propose testing using both a dossier of evidence provided by the Original Equipment Manufacturer (OEM) alongside selected use of track testing. More capable systems will not rely only on warning strategies but will also include intervention strategies when a driver is not attentive. The roadmap for future OSM protocol development could consider a range of known and emerging safety risks including driving while intoxicated by alcohol or drugs, cognitive distraction, and the driver engagement requirements for supervision and take-over performance with assisted and automated driving features.

Communicating Intent of Automated Vehicles to Pedestrians.

While traffic signals, signs, and road markings provide explicit guidelines for those operating in and around the roadways, some decisions, such as determinations of "who will go first," are made by implicit negotiations between road users. In such situations, pedestrians are today often dependent on cues in drivers' behavior such as eye contact, postures, and gestures. With the introduction of more automated functions and the transfer of control from the driver to the vehicle, pedestrians cannot rely on such non-verbal cues anymore. To study how the interaction between pedestrians and automated vehicles (AVs) might look like in the future, and how this might be affected if AVs were to communicate their intent to pedestrians, we designed an external vehicle interface called automated vehicle interaction principle (AVIP) that communicates vehicles' mode and intent to pedestrians. The interaction was explored in two experiments using a Wizard of Oz approach to simulate automated driving. The first experiment was carried out at a zebra crossing and involved nine pedestrians. While it focused mainly on assessing the usability of the interface, it also revealed initial indications related to pedestrians' emotions and perceived safety when encountering an AV with/without the interface. The second experiment was carried out in a parking lot and involved 24 pedestrians, which enabled a more detailed assessment of pedestrians' perceived safety when encountering an AV, both with and without the interface. For comparison purposes, these pedestrians also encountered a conventional vehicle. After a short training course, the interface was deemed easy for the pedestrians to interpret. The pedestrians stated that they felt significantly less safe when they encountered the AV without the interface, compared to the conventional vehicle and the AV with the interface. This suggests that the interface could contribute to a positive experience and improved perceived safety in pedestrian encounters with AVs - something that might be important for general acceptance of AVs. As such, this topic should be further investigated in future studies involving a larger sample and more dynamic conditions.

Analysis of the mechanism of injury in non-fatal vehicle-to-pedestrian and vehicle-to-bicyclist frontal crashes in Sweden.

The aim of this paper is to analyse and compare injuries and injury sources in pedestrian and bicyclist non-fatal real-life frontal passengercar crashes, considering in what way pedestrian injury mitigation systems also might be adequate for bicyclists. Data from 203 non-fatal vehicle-to-pedestrian and vehicle-to-bicyclist crashes from 1997 through 2006 in a city in northern Sweden were analysed by use of the hospitals injury data base in addition to interviews with the injured. In vehicle-to-pedestrian crashes (n = 103) head and neck injuries were in general due to hitting the windscreen frame, while in vehicle-to-bicycle crashes (n = 100) head and neck injuries were typically sustained by ground impact. Abdominal, pelvic and thoracic injuries in pedestrians and thoracic injuries in bicyclists were in general caused by impacting the bonnet. In vehicle-to-pedestrian crashes, energy reducing airbags at critical impact points with low yielding ability on the car, as the bonnet and the windscreen frame, might reduce injuries. As vehicle-to-bicyclist crashes occurred mostly in good lighting conditions and visibility and the ground impact causing almost four times as many injuries as an impact to the different regions of the car, crash avoidance systems as well as separating bicyclists from motor traffic, may contribute to mitigate these injuries.

Pretensioner loading to rear-seat occupants during static and dynamic testing.

OBJECTIVE: Pretensioners reduce the seat belt slack and couple the occupant early to the restraint system. There is a growing prevalence of rear seat pretensioners and it is essential to determine whether the load from the pretensioner itself can cause injuries to rear-seated children. The aim of the study was to investigate the loading to the neck, chest, and abdomen of various sizes of anthropometric test devices (ATDs) during the pretensioner deployment phase and the crash phase in low-severity frontal sled tests and during static deployment. METHODS: Low-severity frontal sled tests were conducted with the Hybrid III (HIII) 3-year-old, HIII 6-year-old, HIII 5th percentile, and HIII 50th percentile ATDs. Two different retractor pretensioners with varying pretensioner force were used. The child ATDs were restrained on a booster cushion (BC), with and without a back. The loading to the neck and chest was compared to injury assessment reference values (IARVs) reported by Mertz et al. (2003). The chest loading to the HIII 5th percentile and HIII 50th percentile ATDs was also analyzed using age-related injury risk curves. Static pretensioner tests with the Q-series 10-year-old ATD, equipped with an advanced abdominal loading device, were conducted in standard ATD position and out-of-position with the lap belt positioned high on the abdomen. RESULTS: During the crash phase, head excursion and neck loading were reduced for both pretensioners for all ATDs compared to testing without a pretensioner. The pretensioner reduced chest deflection to the adult ATDs but not to child ATDs when seated on a BC with a back during the crash phase. When the back was removed, chest deflection was reduced below IARV. The head excursion was reduced for all ATDs with both pretensioners. During the pretensioner deployment phase, the chest deflection exceeded the IARV for the HIII 3-year-old with the stronger pretensioner when seated on booster with a back and it was reduced below the IARV with the lower force pretensioner. For all ATDs, neck and chest loading during the pretensioner deployment phase were reduced when a pretensioner with lower force was used. Abdominal loading to the Q10 in the static pretensioner deployments indicated a low risk of abdominal injury in all tested positions. CONCLUSION: This study indicates the need to balance the pretensioner force and seat belt geometry to gain good pretensioner performance in both the pretensioner deployment phase and the crash phase.

A real-life based evaluation method of deployable vulnerable road user protection systems.

OBJECTIVE: The aim of this study was to develop a real-life-based evaluation method, incorporating vulnerable road user (VRU) full-body loading to a vehicle with a deployable protection system in relevant test setups, and use this method to evaluate a prototype pedestrian and cyclist protection system. METHODS: Based on accident data from severe crashes, the most common scenarios were selected and developed into 5 test setups, 2 for pedestrians and 3 for bicyclists. The Polar II pedestrian anthropomorphic test device was used, either standing or on a standard bicycle. These test setups could then be used to evaluate real-life performance of a prototype protection system, regarding both positioning and protection, for vulnerable road users. The protection system consisted of an active hood and a windshield airbag and was mounted on a large passenger car with a conventional hood-type front end. Injury evaluation criteria were selected for head, neck, and chest loading derived from occupant frontal and side impact test methods. RESULTS: The protection system managed to be fully deployed, obtaining the intended position in time-that is, before VRU body contact-in all test setups, and head protection potential was not negatively influenced by the preceding thoracic impact. Head loading resulted in head injury criterion (HIC) values ranging up to 4400 for the standard car, and all HIC values were below 650 with the protection system. The risk of severe (Abbreviated Injury Scale [AIS] 3+) head injury decreased from 85% to 100% in 3 test setups (mainly to the windscreen frame), to less than a 20% risk in all setups. In general, there were larger differences between structures impacted than between the pedestrian and cyclist setup. Neck loading was maintained at an acceptable level or was slightly decreased by the protection system, and chest loading was decreased from high values in 2 test setups in which the cyclist was impacted laterally with chest impact mainly to the hood area. CONCLUSIONS: A test method was developed to evaluate a more real-life-based test condition, as a complement to current component test methods. Being real-life based, including full-body loading, it is suggested as a complementary test method to the more simplified legal and rating component tests. Together these test methods will provide a more thorough evaluation of a protection system. The evaluated protection system performed well regarding both positioning and protection, indicating a capability to obtain the intended position in time with the potential to prevent the most common severe upper-body injuries of a pedestrian or cyclist in typical real-life accidents, without introducing negative side effects.

Correlation Between Euro NCAP Pedestrian Test Results and Injury Severity in Injury Crashes with Pedestrians and Bicyclists in Sweden.

Pedestrians and bicyclists account for a significant share of deaths and serious injuries in the road transport system. The protection of pedestrians in car-to-pedestrian crashes has therefore been addressed by friendlier car fronts and since 1997, the European New Car Assessment Program (Euro NCAP) has assessed the level of protection for most car models available in Europe. In the current study, Euro NCAP pedestrian scoring was compared with real-life injury outcomes in car-to-pedestrian and car-tobicyclist crashes occurring in Sweden. Approximately 1200 injured pedestrians and 2000 injured bicyclists were included in the study. Groups of cars with low, medium and high pedestrian scores were compared with respect to pedestrian injury severity on the Maximum Abbreviated Injury Scale (MAIS)-level and risk of permanent medical impairment (RPMI). Significant injury reductions to both pedestrians and bicyclists were found between low and high performing cars. For pedestrians, the reduction of MAIS2+, MAIS3+, RPMI1+ and RPMI10+ ranged from 20-56% and was significant on all levels except for MAIS3+ injuries. Pedestrian head injuries had the highest reduction, 80-90% depending on level of medical impairment. For bicyclist, an injury reduction was only observed between medium and high performing cars. Significant injury reductions were found for all body regions. It was also found that cars fitted with autonomous emergency braking including pedestrian detection might have a 60-70% lower crash involvement than expected. Based on these results, it was recommended that pedestrian protection are implemented on a global scale to provide protection for vulnerable road users worldwide.

Pedestrian Injuries By Source: Serious and Disabling Injuries in US and European Cases.

US and European pedestrian crash cases were analyzed to determine frequency of injury by body region and by the vehicle component identified as the injury source. US pedestrian data was drawn from the Pedestrian Crash Data Study (PCDS). European pedestrian data was drawn from the German In-Depth Accident Study (GIDAS). Results were analyzed in terms of both serious injury (AIS 3+) and disabling injury estimated with the Functional Capacity Index (FCI). The results are presented in parallel for a more complete international perspective on injuries and injury sources. Lower extremity injury from bumper impact and head&face injury from windshield impact were the most frequent combinations for both serious and disabling injuries. Serious lower extremity injuries from bumper contact occurred in 43% of seriously injured pedestrian cases in US PCDS data and 35% of European GIDAS cases. Lower-extremity bumper injuries also account for more than 20% of disability in both datasets. Serious head &face injuries from windshield contact occur in 27% of PCDS and 15% of GIDAS serious injury cases. While bumper impacts primarily result in lower extremity injury and windshield impacts are most often associated with head & face injuries, the hood and hood leading edge are responsible for serious and disabling injuries to a number of different body regions. Therefore, while it is appropriate to focus on lower extremity injury when studying bumper performance and on head injury risk when studying windshield impact, pedestrian performance of other components may require better understanding of injury risk for multiple body regions.

Fatal Vehicle-to-Bicyclist Crashes in Sweden - an In-Depth Study of injuries and vehicle sources.

Designing effective vehicle-based countermeasures for vulnerable road users demands an understanding of the relationship between injury and injury source. The aim of this study was to explore this association for bicyclists in fatal real-life-crashes. All fatal crashes in Sweden where a bicyclist was killed when hit by the front of a passenger car between 2002 and 2008 were studied in detail using on-scene data. An analysis was performed to determine the body region containing the injury causing death, and the point of the car accountable for the fatal injury. These crashes were then compared to a previous study with the same selection criteria for vehicle-to-pedestrian fatal crashes.A combined analysis revealed that the dominating injury mechanism was head/neck injury from the windshield area. The most frequent injurious windshield parts were structural; the frame and lower parts of the glass area with instrument panel situated within the head's line of motion. This study indicates that bicyclists' injury sources were located more rearwardly on the car (e.g. windshield relative to hood), in comparison to injury sources in fatal vehicle-to-pedestrian crashes.If countermeasures to prevent fatal bicyclist injury in vehicle impacts were to be concentrated on mitigating head and thorax impact to the structural parts of the windshield, a dominant share of fatal bicyclist crashes could be prevented. This study shows that pedestrian countermeasures also have a potential for reducing injury in bicyclist crashes, but indicating that these countermeasures should be extended to address higher areas of the windshield.

Potential of pedestrian protection systems--a parameter study using finite element models of pedestrian dummy and generic passenger vehicles.

OBJECTIVE: To study the potential of active, passive, and integrated (combined active and passive) safety systems in reducing pedestrian upper body loading in typical impact configurations. METHODS: Finite element simulations using models of generic sedan car fronts and the Polar II pedestrian dummy were performed for 3 impact configurations at 2 impact speeds. Chest contact force, head injury criterion (HIC(15)), head angular acceleration, and the cumulative strain damage measure (CSDM(0.25)) were employed as injury parameters. Further, 3 countermeasures were modeled: an active autonomous braking system, a passive deployable countermeasure, and an integrated system combining the active and passive systems. The auto-brake system was modeled by reducing impact speed by 10 km/h (equivalent to ideal full braking over 0.3 s) and introducing a pitch of 1 degree and in-crash deceleration of 1 g. The deployable system consisted of a deployable hood, lifting 100 mm in the rear, and a lower windshield air bag. RESULTS: All 3 countermeasures showed benefit in a majority of impact configurations in terms of injury prevention. The auto-brake system reduced chest force in a majority of the configurations and decreased HIC(15), head angular acceleration, and CSDM in all configurations. Averaging all impact configurations, the auto-brake system showed reductions of injury predictors from 20 percent (chest force) to 82 percent (HIC). The passive deployable countermeasure reduced chest force and HIC(15) in a majority of configurations and head angular acceleration and CSDM in all configurations, although the CSDM decrease in 2 configurations was minimal. On average a reduction from 20 percent (CSDM) to 58 percent (HIC) was recorded in the passive deployable countermeasures. Finally, the integrated system evaluated in this study reduced all injury assessment parameters in all configurations compared to the reference situations. The average reductions achieved by the integrated system ranged from 56 percent (CSDM) to 85 percent (HIC). CONCLUSIONS: Both the active (autonomous braking) and passive deployable system studied had a potential to decrease pedestrian upper body loading. An integrated pedestrian safety system combining the active and passive systems increased the potential of the individual systems in reducing pedestrian head and chest loading.

Priorities of pedestrian protection--a real-life study of severe injuries and car sources.

The aim of this study was to aid the optimisation of future, vehicle based, pedestrian injury countermeasures. The German In-Depth Accident Study (GIDAS) database was queried for pedestrians impacted by the front of a passenger car or van. A total of 1030 cases from 1998 to 2008 were studied including 161 severely (AIS3+) injured pedestrians. Considering the severe injuries, the most frequent injury mechanisms were "leg-to-front end", "head-to-windscreen area", "chest-to-bonnet area", and "chest-to-windscreen area". For children, a "head-to-bonnet area" impact was the second most common source of injury. With safety systems targeting these five injury mechanisms, 73% (95% confidence interval [CI], 65-81%) of the severely injured pedestrians would be provided protection from all of their vehicle-induced severe injuries. Omitting the windscreen area, this figure is decreased to 44% (CI, 36-53%). Furthermore, 31% of the surviving pedestrians were estimated to sustain a permanent medical impairment at any level. For more severe impairment, head was the dominating body region. The study shows that when developing countermeasures for the windscreen area to mitigate head injuries, attention should be paid to the structural parts of the windscreen area with a special focus on brain injuries. Finally, the incidence and risk of severe injury were derived as functions of impact speed for different body regions and injury sources.

Pedestrian injury mitigation by autonomous braking.

The objective of this study was to calculate the potential effectiveness of a pedestrian injury mitigation system that autonomously brakes the car prior to impact. The effectiveness was measured by the reduction of fatally and severely injured pedestrians. The database from the German In-Depth Accident Study (GIDAS) was queried for pedestrians hit by the front of cars from 1999 to 2007. Case by case information on vehicle and pedestrian velocities and trajectories were analysed to estimate the field of view needed for a vehicle-based sensor to detect the pedestrians one second prior to the crash. The pre-impact braking system was assumed to activate the brakes one second prior to crash and to provide a braking deceleration up to the limit of the road surface conditions, but never to exceed 0.6 g. New impact speeds were then calculated for pedestrians that would have been detected by the sensor. These calculations assumed that all pedestrians who were within a given field of view but not obstructed by surrounding objects would be detected. The changes in fatality and severe injury risks were quantified using risk curves derived by logistic regression of the accident data. Summing the risks for all pedestrians, relationships between mitigation effectiveness, sensor field of view, braking initiation time, and deceleration were established. The study documents that the effectiveness at reducing fatally (severely) injured pedestrians in frontal collisions with cars reached 40% (27%) at a field of view of 40 degrees. Increasing the field of view further led to only marginal improvements in effectiveness.

Influence of impact speed on head and brain injury outcome in vulnerable road user impacts to the car hood.

EuroNCAP and regulations in Europe and Japan evaluate the pedestrian protection performance of cars. The test methods are similar and they all have requirements for the passive protection of the hood area at a pedestrian to car impact speed of 40 km/h. In Europe, a proposal for a second phase of the regulation mandates a brake-assist system along with passive requirements. The system assists the driver in optimizing the braking performance during panic braking, resulting in activation only when the driver brakes sufficiently. In a European study this was estimated to occur in about 50% of pedestrian accidents. A future system for brake assistance will likely include automatic braking, in response to a pre-crash sensor, to avoid or mitigate injuries of vulnerable road users. An important question is whether these systems will provide sufficient protection, or if a parallel, passive pedestrian protection system will be necessary. This study investigated the influence of impact speed on head and brain injury risk, in impacts to the carhood. One car model was chosen and a rigid adjustable plate was mounted under the hood. Free-flying headform impacts were carried out at 20 and 30 km/h head impact velocities at different under-hood distances, 20 to 100 mm; and were compared to earlier tests at 40 km/h. The EEVC WG17 adult pedestrian headform was used for non-rotating tests and a Hybrid III adult 50th percentile head was used for rotational tests where linear and rotational acceleration was measured. Data from the rotational tests was used as input to a validated finite element model of the human head, the Wayne State University Head Injury Model (WSUHIM). The model was utilized to assess brain injury risk and potential injury mechanism in a pedestrian-hood impact. Although this study showed that it was not necessarily true that a lower HIC value reduced the risk for brain injury, it appeared, for the tested car model, under-hood distances of 60 mm in 20 km/h and 80 mm in 30 km/h reduced head injury values for both skull fractures and brain injuries. An earlier study showed that the corresponding value for a test speed of 40 km/h is 100 mm. A 10 km/h reduction in head impact velocity, as in automatic braking, allowed 20 mm less under-hood clearance with maintained head protection of the vulnerable road user.