Objective: To determine whether varying the seat belt load limiter (SBL) according to crash and occupant characteristics could have real world injury reduction benefits in frontal impacts and if so, to quantify those benefits. Methods:Real world UK accident data were used to identify the target population of vehicle occupants and frontal crash scenarios where improved chest protection could be most beneficial. Generic baseline driver and front passenger numerical models using a 50 th percentile dummy were developed with MADYMO software.Simulations were performed where the load limiter threshold was varied in selected frontal impact scenarios.For each SBL setting, restraint performance, dummy kinematics and injury outcome were studied in five different frontal impact types. Thoracic injury predictions were converted into injury probability values using AIS 2+ age dependent thoracic risk curves which were developed and validated based on a methodology proposed by Laituri et al. (2005). Real world benefit was quantified using the predicted AIS 2+ risk and assuming an appropriate adaptive system was fitted to all the cars in a real world sample of recent frontal crashes involving European passenger cars. Results:From the accident data sample the chest was the most frequently injured body region at an AIS 2+ level in frontal impacts (7% of front seat occupants). The proportion of older vehicle front seat occupants (>64 years) with AIS 2+ injury was also greater than the proportion of younger occupants. Additionally, older occupants were more likely to sustain seat belt induced serious chest injury in low and moderate speed frontal crashes. In both front seating positions, the low SBL provided the best chest injury protection, without increasing the risk to other body regions. In severe impacts, the low SBL allowed the driver to move dangerously close to the steering wheel. Compared to the driver side, greater ride down space on the passenger side gave a higher potential for using the low SBL's. When applying the AIS 2+ risk reduction findings to the weighted accident data sample, the risk of sustaining an AIS 2+ seat belt injury changed to 0.9%, 4.9% and 8.1%for young, mid and older occupants respectively from their actual injury risk of 1.3%, 7.6% and 13.1%. Conclusions:These results suggest the potential for improving the safety of older occupants with the development of smarter restraint systems. This is an important finding since the number of older users is expected to increase rapidly over the next 20 years. The greatest benefits were seen at lower crash severities. This is also important since most real world crashes occur at lower speeds.
The introduction of automated L5 driving technologies will revolutionise the design of vehicle interiors and seating configurations, improving occupant comfort and experience. It is foreseen that pre-crash emergency braking and swerving manoeuvres will affect occupant posture, which could lead to an interaction with a deploying airbag. This research addresses the urgent safety need of defining the occupant’s kinematics envelope during that pre-crash phase, considering rotated seat arrangements and different seatbelt configurations. The research used two different sets of volunteer tests experiencing L5 vehicle manoeuvres, based in the first instance on 22 50th percentile fit males wearing a lap-belt (OM4IS), while the other dataset is based on 87 volunteers with a BMI range of 19 to 67 kg/m2 wearing a 3-point belt (UMTRI). Unique biomechanics kinematics corridors were then defined, as a function of belt configuration and vehicle manoeuvre, to calibrate an Active Human Model (AHM) using a multi-objective optimisation coupled with a Correlation and Analysis (CORA) rating. The research improved the AHM omnidirectional kinematics response over current state of the art in a generic lap-belted environment. The AHM was then tested in a rotated seating arrangement under extreme braking, highlighting that maximum lateral and frontal motions are comparable, independent of the belt system, while the asymmetry of the 3-point belt increased the occupant’s motion towards the seatbelt buckle. It was observed that the frontal occupant kinematics decrease by 200 mm compared to a lap-belted configuration. This improved omnidirectional AHM is the first step towards designing safer future L5 vehicle interiors.
Objective: This study aimed to explore how pedestrians safety perception concerning the built environmental characteristics can assist in designing a safer built environment in an urban area in Mexico. Methods: The study involved two stages of data collection. In the first stage, a physical audit on selected urban roads was performed to assess the characteristics that may increase the perceived risk of a collision. An observational framework to evaluate the crossing areas, sidewalks and organizational factors was developed and used for data collection. In the second stage, an on-street questionnaire was applied to collect the perception of a group of 299 pedestrians about safety risks, road characteristics and their ideas for designing a safer built environment. Results: The physical road audit identified several features in the crossing areas and sidewalks, such as parked cars, movable and fixed obstacles, and lack of traffic signage, which may increase the risk of a pedestrian being involved in a collision. More than half of the road users who were interviewed either agree (27%) or strongly agree (29%) with the statement that crossing the roads in the area was safe. However, pedestrians also identified the following elements as detrimental for the safe use of roads: lack of traffic lights, too much traffic, lack of signs, and parked cars that obstruct visibility. Participants also raised issues beyond the physical infrastructure; for instance, a lack of respect shown by drivers to pedestrians. For designing a safer built environment, participants suggested several ideas highlighting pedestrianization of the road and widening the sidewalks, along with restricting parking of cars on the road. Conclusions: This combination of findings provide valuable support for the premise that pedestrians may have a good sense of recognizing safety problems and the ability to see the solutions. Although the research was undertaken in the context of a municipality in Guadalajara, the role of pedestrian safety perception may be applicable in other urban settings in low and middle-income countries (LMICs), where local authorities are in charge of designing the road environment. This study highlights the relevance of including pedestrians' participation for a safer and human-centred design of our cities.
Objective: Improving crash protection for older car occupants is a matter of urgency since the number of older car users is forecast to grow dramatically over the next two decades. The thorax is particularly vulnerable in older occupants, and this study aimed to provide real-world in-depth analysis of factors contributing to chest injuries in frontal impacts involving European cars. Methods: Real world crash injury data were interrogated, focusing on cars with current restraint components. The research examined belted front-seat occupants in frontal impacts where air bags, pretensioners and load limiters were present. Results: The chest was the most often injured body region at AIS 2+, 3+ and 4+ injury levels. The rate of AIS 2+ and AIS 3+ chest injuries was highest among elderly occupants and lowest among young occupants, and elderly occupants sustained proportionally more severe chest injuries in low/moderate speed impacts compared to young and middle-aged occupants. However, it should be noted that rates of AIS 2 chest injury were also significantly higher for middle-aged occupants compared to the young. The front passenger seat was shown to be more often associated with significant chest injury than the driver seat. The higher proportion of elderly female occupants was postulated as a reason for this. Skeletal injury was the most frequent type of AIS 2+ chest injury and the rate of injury for elderly occupants with such injuries was higher than for young and middle-aged occupants. With the increase in the number of rib fractures, the risk of pulmonary complications and organ injuries tended to increase. The major cause of chest injury was identified as restraining loads transmitted to the chest via the seat belt. The absence of intrusion in the majority of cases, suggests an opportunity for the restraint system to better manage the crash pulse. Not only for elderly occupants but for those who are middle-aged as well. Conclusions: This study shows the necessity for safety interventions, through new vehicle crashworthiness systems to improve chest protection especially for middle aged and elderly car occupants. Deployment of appropriate injury risk criteria, use of an appropriate dummy thorax, development of a low energy restraint test, and the development of more adaptive restraints have been discussed as possible solutions to the problem.
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