包摂的な衝突試験用ダミー：標準モデルと参照モデルの再考

The Challenge

In engineering design, the medium-sized male body (175 cm; 75.5 kg) has been taken as the norm. It is no surprise then than men fitting this profile suffer the fewest injuries in automobile accidents (Carter et al., 2014).

When crash data is analyzed by sex, age, height, and weight, injury rates are higher among people who don’t fit the mid-sized male norm. Elderly drivers have high fatality rates per vehicle mile driven (Augenstein et al., 2003). Obese drivers also risk death and serious injury. And women are more likely than men to be injured in crashes. When considering the compounding interaction of these factors, elderly females and obese males suffer greater injury in crashes of equal severity than the “standard” male (Carter et al., 2014).

Gendered Innovation 1: Expanding Established Norms

Numerous efforts are underway to expand computational models to represent greater diversity of human bodies, such as properly modeled females (Östh et al., 2016), elderly and overweight females and males, (Hu et al., 2012), and children (Carter et al., 2014). Still lacking are physical crash dummies to model these populations, with the exception of children (see Method: Rethinking Standards and Reference Models).

Females: Women are involved in fewer severe automobile crashes overall, but when they are involved in a crash, they are more likely to sustain serious injuries, even when using seat belts. National U.S. automotive crash data from 1998 to 2008 revealed that the odds for a belt-restrained female driver to sustain severe injuries were 47% higher than those for a belt-restrained male driver involved in a comparable crash, when controlling for weight and body mass (Bose et al., 2011).

Crash test dummies designed to represent the 5th percentile “female” by height and weight (151 cm, 47.3 kg) were developed beginning in 1966, but these are only scaled-down versions of the standard, mid-sized male and not modeled on the female population. Thus, the 5th percentile dummy does not represent the average: 1) female geometry, such as the shape and form of the torso; 2) female muscle and ligament strength; 3) female spinal alignment; 4) female dynamic responses to trauma; 5) mass distribution of different body parts (Linder & Svedberg, 2019) (see Method: Analyzing Sex).

Researchers have developed a computer model of a 50th percentile female low severity impact dummy—the EvaRID—and a physical prototype of a 50th percentile female dummy—the BioRID 50F. But these models have not yet lead to commercially produced dummies for use in national automotive testing either in Europe or in the U.S. (Linder et al., 2013a; Linder et al., 2013b; Hu, et al. 2012). For certain tests, a 5th percentile dummy is included only in the passenger seat (apparently assuming that women don’t drive; Linder & Svedberg, 2019).

Obese People: The 50th percentile male dummy used in tests today represents the average height and weight of men in the late 1970s and early 1980s (Schneider et al., 1983). Today, the U.S. Centers for Disease Control classify almost 40 percent of Americans as obese (Centers for Disease Control, 2018). People with high Body Mass Index (BMI) are more likely to suffer severe lower extremity and thorax injuries in crashes than people with low BMI (Carter et al., 2014). Data from field tests, cadaver tests, and computational studies have shown that increased body mass causes obese individuals to move forward in a frontal crash, increasing the risk of injury to the thorax and the knee, thigh, and hip complex (Hu et al., 2012).

Elderly: Populations in many countries are aging. By 2030, over 25% of the populations in Europe and North American are expected to be over age 60 (United Nations, 2015). National U.S. data show that older people are more likely to experience serious injuries in almost every crash type (Carter et al., 2014). Older people have less dense bones and experience changes to the thorax region which increase injury risk. Older women are at the greatest risk of bone fracture (Hu et al., 2012).

Gendered Innovation 2: Pregnant Computer Crash Simulations

The advances discussed above systematically exclude pregnant bodies. Conventional seatbelts do not fit pregnant women properly, and motor vehicle crashes are the leading cause of fetal death related to maternal trauma (Weiss et al., 2001; Acar et al., 2018). Even a relatively minor crash at 56km/h (35 mph) can cause harm. With over 13 million women pregnant across the European Union and United States each year, the use of seatbelts during pregnancy is a major safety concern (Eurostat, 2011; Finer & Kost, 2011).

Seatbelts were first installed in automobiles in the 1950s, and their use became mandatory in the late 1980s and early 1990s. As early as 1967, the American Medical Association advocated the use of seatbelts by pregnant women (Committee, 1972). At that time, little laboratory research in seatbelt design addressed pregnant women, making it difficult to assess the comparative effectiveness of various seatbelt designs and other safety technologies, such as the airbag (Insurance Institute for Highway Safety, 1972). As seatbelt usage increased, injuries caused by lap belts began to raise concerns that seatbelts might be hazardous to the fetus even when mothers are not injured (Committee, 1972).

Current research suggests that pregnant women should use the 3-point seatbelt (McGwin et al., 2004), yet for many women, particularly those who carry low, 3-point seatbelts ride up on the pregnant belly. In a crash, this increases force transmission to the abdomen by three- or four-fold relative to the force transmitted when the belt is worn below the uterus‚ with a corresponding increased risk of fetal injury (Pearlman et al., 1996).

The development of pregnant crash test dummies and computer simulations have the potential to play a key role in increasing seatbelt safety for fetuses.

While improvements to the pregnant crash test dummy (the MAMA-2B created in 1996) are ongoing, in 2002 researchers in the U.S. adapted crash simulation software to model a 5th percentile dummy equipped with a virtual uterus, placenta, and amniotic fluid as well as uterosacral and round ligaments (Moorcroft, 2003). Using this computer model, validated by cadaver and real-world crash data, researchers modeled differences in outcomes between unbelted, belted, and improperly belted pregnant passengers. In 2008, researchers further improved this computer model by adding a realistic 38-week fetus (developed using ultrasound images) and modeling in utero fetal motion during impact (Acar et al., 2009).

In 2002, Volvo also developed a virtual pregnant crash dummy "Linda" in her 36th week of pregnancy . Other car companies and researchers have also used computer models and pregnant crash test dummies in safety testing (Hitosugi et al., 2018; Vladutiu & Weiss, 2012).

Conclusions

Gendered Innovations have led to more inclusive standards for crash test dummies. In 2019, Volvo announced its E.V.A. (Equal Vehicles for All), an initiative that recognizes that virtual models and physical dummies need to represent a greater variety of body types. To this end, they are sharing their research and data from real-world crashes (Volvo, 2019). Academic and industry researchers are now ramping up efforts to expand crash test dummies to better model the human population. Women’s bodies, pregnant bodies, older bodies, and larger bodies, however, are still not standard or required in automobile safety tests.

Next Steps

1. The U.S. National Highway Traffic Safety Administration (NHTSA) currently requires safety testing using dummies modeling average and small male bodies, but not 95th percentile males, elderly people, obese people, pregnant women, or female bodies (the 5th percentile female is a scaled-down male dummy). The European New Car Assessment Programme (Euro NCAP) utilizes the same Hybrid III dummies as prescribed by the U.S. NHTSA, and as a result does not model a wide range of bodies in crash tests (Euro NCAP, 2010; Euro NCAP, 2009; Linder, A., & Svedberg W., 2019; Linder, A., & Svensson, M., 2019). Governments should mandate vehicle safety testing using crash test dummies or simulations that represent the anatomical features of both the 50th percentile female and male, pregnant, obese, tall, and elderly bodies.

In 2021, the Furthering Advanced and Inclusive Research for Crash Tests Act (FAIR Crash Tests Act) was introduced into a U.S. Congressional Committee. The Act would order the Government Accountability Office to evaluate NHTSA’s failure to use crash test dummies that represent the driving public, especially women, while assessing vehicle safety through its 5-star safety rating program.

2. The traditional 3-point seatbelt can harm a fetus. Redesigning seatbelts to accommodate pregnancy should become a priority for automobile makers. Private developers have introduced supplementary devices to hold conventional lap belts in place‚ but these have not undergone rigorous government safety testing (Klinich, 2009). A better solution may be a redesign of the conventional 3-point seatbelt to provide greater safety for all passengers.