The impact of sex on crash injury outcomes

Crash test dummies have been used in vehicle testing for decades. In the United States, testing beginning in 1973 with a male test dummy based upon 50th percentile, or average, males. These test dummies were labeled as “adult-sized” test dummies, even though they only represented the structure and measurements of a male body. Vehicle regulations for female occupant dummies did not come into effect until 2003, with a female dummy not being incorporated into the standard for any testing until 2006. However, these “female” test dummies are not structurally representative of female bodies. These dummies are only based upon the dimensions of a 5th percentile female and their makeup is based upon scaled data from a 50th percentile male dummy.

This vehicle testing divide is similar across the globe. These half million dollar crash test dummies do not represent female bodies, but rather scaled down male dummies. Further, even today, only 50th percentile male dummies are used in the driver’s seat in any vehicle testing in the United States. Due to this design error, female drivers are often described as natural “out of position drivers.” This lack of design for females in vehicles has been gaining traction in media recently, from CityLab to Consumer Reports to BBC.

Likely connected with vehicle design, several previous studies have concluded that in comparable crash conditions, female drivers are more likely to experience higher injury severity. One study suggested that these differences, at least in non-fatal cases, are not related to driving skill-level, but rather outside factors. However, to date, it is unknown what the impact driver sex has on all possible primary injury location outcomes in comparable crash conditions using a large-scale data set. This study aimed to fill this literature gap.

Study Setup

UMassSafe developed a new data linkage process connecting crash data from the Massachusetts Crash Data System (CDS), reported by police, and emergency medical services (EMS) data from the Massachusetts Ambulance Trip Record Information System (MATRIS). Using this new linked data of crashes from 2015 to 2016, primary injury location, driver sex, driver age, airbag deployment, first harmful event in crash, and manner of collision were used to explore relationships. Binary logistic modeling and k-fold cross validation were used in both the explanatory analysis and predictive analysis of 26,015 cases, along with a variety of reporting methods.

The Impact of Sex on Driver Injury

Likelihood of Primary Injury Location Outcome (Reference: Male Driver)

The odds ratios represent the odds that a particular outcome will occur given certain exposure. An odds ratios equal to one represents that female drivers are not at a higher risk of that specific injury than male drivers are. An odds ratio greater than one represents that female drivers have lower odds than male drivers of having a specific injury outcome. Finally, an odds ratio less than one represents the opposite; that female drivers have higher odds of having a specific injury outcome than male drivers.

These results highlight the injuries that female drivers are more likely to experience than male drivers in EMS responsive crashes in comparable conditions.

The Takeaway

An EMS responsive crash resulting in no injury is 24% less likely to be a female driver than a male driver, representing that male drivers are less likely to have any injury in these conditions. Overall, female drivers are more likely than male drivers to experience their primary injury in their abdomen by 97%, chest by 17%, lower extremity by 27%, and neck by 17%. On the other hand, male drivers are more likely to have their primary injury in their back by 25% or generally/globally by 8% compared to female drivers. Given this information, researchers, vehicle designers, and vehicle testers should consider the vehicle design components which may increase injury risk for female drivers compared to male drivers.

As an example, female drivers were found to be at an increased risk of neck injuries. This may be caused by vehicle design and testing, which does not account for the height of females and the placement of their neck against a headrest, as well as the lower total neck muscle volume that females have compared to males.

Given that the current design standards of vehicles revolve around the male body structure, the primary injury locations found to be more prominent and significant in female driver crashes compared to male driver crashes provide insight into potential design features that future safety technology design could (and should) consider. Overall, it is necessary and equitable to provide in-vehicle safety technology that accounts for the varying body structures of all drivers and occupants.

Read the full paper for details:

The impact of sex on motor vehicle crash injury outcomes. Alyssa Ryan, Francis Tainter, Cole Fitzpatrick, Jennifer Gazzillo, Robin Riessman, and Michael Knodler. Journal of Transportation Safety & Security (2020).