Q: Why does SENIORS still see potentials in passive instead of active vehicle safety systems which, more and more, are entering the market being able to avoid road traffic accidents?
R: Although active vehicle safety systems, especially emergency braking systems, promise a large potential to avoid or mitigate road traffic crashes, their market penetration requires time and further development loops are needed to tune them to deliver their full safety potential by also covering a wide range of realistic traffic scenarios. Remember, crashes are often unique incidents that are difficult to predict and where multiple parameters interact with each other in a very short time. SENIORS encourages innovative passive vehicle safety systems that will either act subsequently as part of the integrated safety or as the sole system operating in a high number of crashes. The project partners are convinced that adapted passive vehicle safety systems are required to reach the internationally set goals for the road injury statistics in near- to mid-term.
Q: Biomechanics is a key word in SENIORS. What is biomechanics and why is it required?
R: Related to humans, biomechanics is where mechanical engineering and biology meet, and describes the effects for the skeletal and musculature system as well as other organs under different loading conditions. In particular regarding crash loadings, there is still little known and related experiments are challenging. In SENIORS, the obtained data is transferred e.g. into numerical models and hardware test tools that allow continuing basic research and assessing safety systems more realistically. Without this knowledge, no specific injury estimates could be made. In general, far more biomechanical research is required to understand better the diversity of human response to crash loads and to be able to choose most effective measures in the road traffic safety area.
Q: How can computer simulations help to improve the safety of older road users?
R: SENIORS considers the latest crash and biomechanical information that allows to distinguish between younger and older road users. For example, the change of the rib cage by age, in particular regarding its material properties and geometry, is considered and allows the modification of finite element human body models towards more precise thorax injury predictions. These tools still require various development steps, but will definitely support the development of effective safety systems that finally helps both, older and younger road users.
Globally, the number of older persons (those aged 60 years or over) is growing faster than the numbers of people in any other age group and, that growth, is projected to accelerate in the coming years. By 2030, older persons will outnumber children aged 0-9 years (1.4 billion versus 1.3 billion); by 2050, there will be more people aged 60 years or over than adolescents and youth aged 10-24 years (2.1 billion versus 2.0 billion).
This fact is poised to become one of the most significant social transformations of the twenty-first century, with implications for nearly all sectors of society, including the demand for goods and services, such as housing, transportation and social protection.
In an ageing society, the European Project SENIORS (funded under the H2020 framework programme) aims at improving the safe mobility of older road users. In order to increase the elderly’s level of safe mobility, the characteristics of current road traffic collisions, involving the elderly and the injuries that they sustain, need to be understood in detail.
SENIORS has complemented existing knowledge from previous projects with many crash and hospital datasets regarding older (65 years and older), overweight and obese road users in order to obtain a more complete picture of their injury patterns. The results obtained have been compared with the results of mid-aged road users (25-64 years) by determining the body regions most frequently and severely injured, specific injuries sustained and types of crashes involved to derive safety strategies for automotive applications. The results were prepared on macroscopic and microscopic levels considering the official injury severity classifications “slightly, seriously and fatally injured” and the detailed AIS coding and determination of specific, frequent injuries.
The road traffic accident analysis revealed that injury severity increases with the age of the casualties and varies for specific body regions of different road user types. The elderly suffered in all body regions more often from higher injury severities (AIS 2 and AIS 3+) compared with younger road users in these crashes. Recent statistics have revealed that the 75-84 age group was shown to have the highest fatality rate while the 65-74 group had the lowest. These differences were put down to reduced personal mobility with increasing age and the greater frailty of elderly persons.
The results also show differences in gender fatalities where almost two-thirds of the elderly fatalities were men. However, women made up a higher proportion of fatalities among the elderly (36%) than within the whole population (24%). Figure 1 shows the injury distributions for different age groups and road user types in all kinds of road traffic crashes.
Elderly car occupants are overrepresented in the road injury statistics
Seniors of today are more mobile than seniors of earlier generations leading to an increase in the number of elderly road users and consequently the risk of being involved in crashes.
The increased number of elderly drivers on the roads has an important impact on their share in crash accidents. Drivers over 65 years old involved in crash accidents represent 8% of the car accidents analysed, but elderly drivers’ incidence in traffic is lower – people over 65 make up 4.6% of all the trips performed by private vehicles. This shows the increasing importance of addressing safety of the elderly in road traffic. In terms of gender, the statistics have shown that older females suffer slightly more frequently from a serious or fatal injury outcome than males of this age group. The analysis performed focused on car occupants in passenger cars manufactured in 2005 or later.
Studies of injuries in elderly car occupants have identified a critical body region of concern: the thorax. The thorax is the most critical body region for car occupants, for severe injuries (AIS 3+ levels), see Figure 2, and the risk of thorax injury is at least twice as high for older car occupants than for the mid-aged ones.
External road users also at risk
More than one third of elderly fatalities in the EU-24 countries are pedestrians. Contrary to common perception, most times pedestrian traffic accidents occur when walking or crossing properly. In the case of people over 75 years, these represent 65% of all cases.
The likelihood of these older pedestrians hitting a car’s front and suffering from MAIS 2+ injuries is considerably higher than for mid-aged pedestrians by around 10 percentage points, see Figure 3. The studies carried out have detected injury priorities that differ from the mid-aged ones. The critical areas observed both for elderly pedestrians as for elderly cyclists, with severe (AIS3+) injuries, are located on the lower extremities; head and thorax, being the most injured body regions. The analysis performed focused on pedestrians or cyclists in crashes with passenger cars manufactured in 2006 or later.
The road injury statistics also distinguish different priorities in terms of gender. Male pedestrians sustain more severe thorax injuries and less pelvis injuries in comparison to females. In addition, females suffer less from severe head injuries compared to male pedestrians. Overall, severe injuries to older pedestrians were strongly biased towards females. In contrast, cyclist injuries were heavily biased towards males, while injuries to older pedestrians were strongly biased towards females.
Overall, based on the results from the crash data and analyses, older persons were found to suffer more often from higher injury severities compared to mid-aged road users. These users have different critical body regions that will be the basis for investigating and assessing the injury reduction, achieved through innovative tools and safety systems.
Additional information can be found in the following references:
Fornells, A., et al. (2017). “Senior Drivers, Bicyclists and Pedestrian Behavior Related with Traffic Accidents and Injuries”. SAE Technical Paper number 2017-01-1397.
Wisch, M., et. al. (2017). “Road Traffic Crashes in Europe Involving Older Car Occupants, Older Pedestrians or Cyclists in Crashes with Passenger Cars – Results from Seniors.” ESV Conference Paper number 2017-01-1397.
Wisch, M., et al. (2017). “Injury Patterns of Older Car Occupants, Older Pedestrians or Cyclists in Road Traffic Crashes with Passenger Cars in Europe–Results from SENIORS.” IRCOBI Conference Proceedings.
Fiorentino, A., et al. (2016). “Behavioural aspects of elderly as road traffic participants and model split.” Derivable Report D1.1.
Wisch, M., et al. (2017). “Road traffic accidents involving the elderly and obese people in Europe incl. investigation of the risk of injury and disabilities.” Deliverable Report D1.2.
For more information on the SENIORS project check out http://www.seniors-project.eu/
Adrià Ferrer, Innovation Project Manager (Applus+ IDIADA). E-mail: email@example.com
In Euro NCAP, there is currently a set of test procedures for evaluating the safety performance of cars when they impact pedestrians. The Euro NCAP test procedures comprise three sub-system impact tests to assess a car’s performance. Separate impactors are used to represent the pedestrian in each main phase of impact with respect to the relevant body loadings. The three impactor types are: a FlexPLI for the assessment of pedestrian lower leg and knee injuries; an upper legform impactor representing the thigh and pelvis to record bending moments and forces; and child and adult head impactors to record head accelerations during impact on the vehicle front including the bonnet leading edge. Each impactor is propelled into the car and the output from the impactor instrumentation is used to establish whether the energy absorbing characteristics of the car are acceptable.
Accident data points on head, thorax and lower extremities as the most relevant body regions not only for the average population, but in particular for the elderly. Consequently, SENIORS is also focusing on the improvement and development of impactors representing these body regions and the definition of test and assessment procedures.
Improving kinematics correlation by adding mass
The overall goal within the external road user branch of SENIORS is the enhancement of the safety of older road users. Taking into account the latest accident data analysis, existing pedestrian test tools for the head and lower extremities will be improved. Prior to prototyping of the improved tools and definition of updated test and assessment procedures, a broad variety of human body model and impactor simulations serve as a basis for further development, as shown in Figure 1.
The need to improve the current headform impactor arises during impacts on angled or curved vehicle surfaces when, sometimes, partly high impactor rotations lead to unrealistic results in terms of linear accelerations and calculated values for the Head Injury Criterion (HIC). The purpose of a new Head Neck Impactor (HNI) is to improve the kinematics correlation and the injury assessment by adding a neck mass. The application of an additional neck mass to the impactor is meant to limit the impactor rotation in these cases, bringing the results back into a more realistic range. Simulations with the head neck impactor already showed at an early stage of the programme that the development derived from the APROSYS project is not yet ready for implementation within consumer or regulatory testing.
The FlexPLI updated with a pedestrian torso mass surrogate (UBM – upper body mass) differs from the previous one in that it has an upper body mass which significantly changes the impact response of the lower limb. Through current test tool FlexPLI, the testing of vehicles with high leading edges cannot always be performed in an appropriate way. The starting point for the improvement of the upper body mass for the FlexPLI and the development of a test procedure were comparative simulations with THUMS and the FlexPLI-UBM against generic vehicle frontends. The FlexPLI-UBM shows a much higher correlation with HBM kinematics and time histories as it can be used to address femur injuries and assess higher vehicles, as can be seen in Figure 2.
HBM as well as impactor simulations with added mass were carried out under identical impact conditions against a generic test rig that was developed out of data from more than 160 actual vehicles and that is representing four different vehicle categories (Sedan, SUV, Sport Car, MPV/Van) with three different frontshapes each category.
In the next step, the impactor will be fine-tuned and transfer functions for the injury parameters (knee elongations and femur and tibia bending moments) will be established before validating the final version with simulations against actual vehicles.
Designing new prediction tools
In addition to the legform and headform impactors, a thorax injury prediction tool is being explored in SENIORS. According to the accident data analysis done [article 1], in terms of AIS 3+ pedestrian and cyclists injuries, the thorax is the most relevant body region for the elderlies . For this reason, SENIORS is focusing on the development of a new test tool for the assessment of thoracic injuries of pedestrian and cyclists named Thorax Injury Prediction Tool (TIPT).
The first promising simulation results with TIPT have indicated that the ES-2 torso is applicable for assessing rib injuries to vulnerable road users at speeds representing consumer or regulatory vehicle speeds of 40 km/h and 35 km/h respectively. However, the results were still not that satisfying in terms of correlations that were aimed to be established, but indicated the general possibility for the development of a test tool with good thoracic injury assessment ability. A modification of the TIPT by adding a weight to the neck or to the neck and the pelvis likewise did not improve the overall results in terms of correlations, but could significantly improve correlations for the 4th rib. Figure 3 shows a comparative of the simulations with THUMS and TIPT.
Furthermore, a simplified simulation setup will be considered to eliminate possible scatter of results due to the usage of the SAE buck. If transfer functions can be established in a next step, the original plan to validate the new tool against actual vehicles will be maintained. Prototyping of a first impactor is planned during a subsequent research project.
Additional information can be found in the following papers:
For more information on the SENIORS project check out http://www.seniors-project.eu/
Inquiries: Adrià Ferrer, Innovation Project Manager (Applus+ IDIADA). E-mail: firstname.lastname@example.org