The optimal position for short-statured drivers consists of a pelvic angle between 112-120 degrees.

1 Build an automotive sled model with the following characteristics:

Automobile “neutral” with a seat, seatbelt, airbag, and steering column

Impact at 40mph

Frontal collision

Adjustable driver position

Wearing seatbelt, which adjusts to the driver position

Airbag deployed upon impact

For initial simulations, 50th FE Rigid Dummy

No other structural safety elements were included in the vehicle sled model in order to focus on the interaction between dummy positioning and the seatbelt and steering column with an airbag.

2 Measure human participants to describe seating position

This was done in order to get a pool of actual sitting positions.

Length and angle measurements taken according to Driver Seat: Relative Position Measurements Chart

A: line of sight from eye to windshield

B: nose to top of steering wheel

C: middle of chest to middle of steering wheel

D: knee to bottom of steering wheel

E: knee to bottom of dashboard

Pelvic Angle (II)

Angles I and III were deemed insignificant and not collected

3 Run sled simulation using human participant data to set positioning for VATD in the crash.

Can adjust VATD by translating or rotating VATD limbs or entire body along the X, Y, or Z axes

4 Post-process simulation: analyze mathematical outputs of the simulation to determine:

chest deflection (mm)

maximum chest acceleration (G)

Chest Severity Index

head acceleration (G)

Head Injury Criteria

This data was compiled into a composite injury score, a method developed to classify total injury score by adding up points from each injury output, wherein the primary indicator is chest deflection and the least important are chest acceleration and CSI.

5 Optimize seating position by identifying subset of high-injury, short-stature occupant models and adjusting parameters to minimize injury severity

*I had to upload a YouTube link because the file was too large.

Optimizing Automotive Seating Position to Reduce Injury Severity in Short-Statured Drivers

Sophie Krajmalnik, Texas Academy of Science, Plano West Senior High School

Teacher: Emily Sharma, Plano West Senior High School

This project’s goal is to determine the optimal seating position for short-statured drivers to reduce injury severity in a frontal collision.

The student researcher was inspired by her own experience. When she began doing her in-car driver’s education in summer 2019, she found that there was no truly safe position for her to drive in as a 5’2” female. If she sat in the car’s default driving position, she couldn’t reach the pedals or see over the steering wheel, while if she adjusted her seat to where she could properly see and reach everything, her head was a foot or less away from the windshield. After looking into this, the student researcher realized that this was not, in fact, an isolated issue, nor her being far too anxious. This is an actual issue.

Cars are a necessary aspect of our modern lives. According to the American Driving Survey (2015-2016) conducted by the Foundation for Traffic Safety, people spend an average of nearly one hour behind the wheel per day. That hour provides countless opportunities to have your life gravely affected, and this disproportionately affects short-statured people, who generally happen to be women.

Short-statured drivers are 47% more likely to be severely injured and 17% more likely to die in a car crash. This discrepancy is due to insufficient vehicle safety guidelines resulting from continued use of physical crash test dummies with limited biofidelity. A prime example of this is the fact that female crash test dummies were introduced 60 years after male dummies, and none of these dummies are anthropomorphically correct. Even today, no testing requires accurate dummies that are representative of the broader population. Most testing is done with a 50th percentile male dummy.

Find the optimal seating position for short-statured drivers that reduces the severity of injury in a frontal collision by performing a multi-physics, in-silica simulation using LS-DYNA to determine force and duration of impact through a range of possible seating positions for drivers of varying stature/anatomy and compare the force to the maximum force the human body can handle depending on their anatomy.

Discussion

This project’s goal is to determine the optimal seating position for short-statured drivers to reduce injury severity in a frontal collision.

In LS-DYNA, an automotive sled model was built. This model was an automobile “neutral” with a seat, seatbelt, airbag, and steering column, with no other structural safety elements included in order to focus on the interaction between dummy positioning and the aforementioned elements. This model also included the impact (40 mph), type of collision (frontal), the airbag being deployed upon impact, and an adjustable driver position of a driver wearing a seatbelt that adjusts to their position. 40 mph was chosen as it is used in standard collision tests performed by the National Institute of Highway Safety. For initial simulations, a 50th percentile FE (Finite Element) Rigid Dummy was used.

Next, real human participants were measured in order to get a pool of actual seating positions. Length measurements were taken from the line of sight (eye to windshield), nose to top of steering wheel, middle of chest to middle of steering wheel, knee to bottom of steering wheel, and knee to bottom of dashboard, as well as the pelvic angle. The human data was then used to set the positioning for the VATD in the crash by rotating or translating the limbs or entire body along the X, Y, or Z axes. The sled simulation was then run.

The mathematical outputs of the simulation were analyzed in post-processing in order to determine chest deflection, maximum chest acceleration, Chest Severity Index, head acceleration, and Head Injury Criteria. This data was compiled into a composite injury score, a method developed to classify total injury score by adding up points from each injury output, wherein the primary indicator is chest deflection and the least important are chest acceleration and CSI.

After completing the simulations and establishing the CIS, it was found that the shortest people (based on percentile and height) had the highest composite injury scores (Composite Injury Score Plot). Participant #15, while a seemingly higher percentile (because of age), was the overall shortest person with some of the most severe injuries, and so was selected for initial optimization. The B, C, and pelvic angle parameters were changed based on the Optimization Method Description Chart in order to find what combination minimized injury severity.

Marginal changes occurred in scenarios with bracketed changes to the position along the X axis and pelvic angle. Larger increases were not considered, as they might not be feasible due to the height of the driver (ex. reaching pedals and steering wheel, and visibility). In the final scenario with “As Seated” head and chest positions and a modified pelvic angle of 112 degrees, the Composite Injury Score decreased by 50%. This change drops the CIS from a high severity to a low severity injury.

This same process was then applied to all of the short-statured drivers. A total of 145 simulations were run, and after performing optimization simulations to the other short-statured drivers, changes to the pelvic angle, specifically a pelvic angle between 112 and 120 degrees, while keeping the head distance as close as possible to the baseline, proved to have the most significant positive change on the injury severity scores. For the drivers whose optimized positions exhibited improved injury severity scores, the overall effect was a 39% reduction in severity.

Conclusion

Drivers do not inherently know the safest position for them to drive in- they can only determine where they can reach the steering wheel and the pedals, have proper visibility, and be comfortable. There are, however, driving positions that are similarly physically realistic that are safer for the driver in a crash scenario. For example, in participant #15, the chest distance is the same as the baseline, but by adjusting the pelvic angle (and the head position by proxy), the injury severity decreases by 50%.

Statement of Support

After performing optimization simulations, half of the participants exhibited a reduction in injury severity. Those who didn’t exhibit a change already had quite safe CIS scores. Changes to the pelvic angle where it was between 112 and 120 degrees while maintaining the baselines head distance had a significant positive change on injury severity scores.

Error Analysis

The following are possible sources of error in this project and its evaluation.

Human response/personal preference: No simulation can accurately include how a human would respond to a car crash, as likely they would know it is coming and try to take measures against that. Humans are also likely to simply have personal preference when it comes to their seating positions.

Human error in measurement collection: There is the likely possibility that error was introduced into the data through human error in data collection.

Insufficient model fidelity: Since a student edition was run, the model is limited to 10,000 finite elements, which might have limited the accuracy of the data results. However, this would only produce marginal changes and not change the statistical significance. Also, only ⅔ of the main measurements were exactly matched.

Applications and Future Plans

Complete the LS-DYNA simulations by getting more human data, running simulations with a 5th percentile, non-rigid dummy, and performing statistical significance tests.

Design a mobile app using data to help the driver make informed seating decisions, like a “calculator”.

Create a sensor to alert the driver of an unsafe driving position to prompt readjustment.

Create a working, if scaled down, prototype that automatically readjusts seat based on safety data.

Simulation Data

The Simulation Data Results Table summarizes the important demographic data from the human measurements, the original and optimized seating positions simulated and the results they respectively produced. Included in the chart are only the participants that were categorized as short-statured, with the limit being under 50th percentile for their biological sex and/or still shorter than a 50th percentile male (5’9”). After working with LS-DYNA, it was found that the most important human measurements to be matched were B (nose to top of steering wheel), C (middle of chest to middle of steering wheel), and the pelvic angle.

Composite Injury Score

The Composite Injury Score (CIS) was developed to easily classify total injury severity by adding up scores from the different parameters using a tiered point system, as indicated in the Composite Injury Score Guidelines pictured above. A lower CIS indicates a higher level of safety. In the CIS, the primary indicator is chest deflection. The least important components are chest acceleration and CSI, and so are given a maximum of three points. The highest HIC score considered safe and therefore for a car to be allowed on the road is 700, and so 700+ is a score of 5 in the CIS.

After completing the simulations and establishing the CIS, it was found that the shortest people (based on percentile and height) had the highest composite injury scores (Composite Injury Score Plot). Participant #15, while a seemingly higher percentile (because of age), was the overall shortest person with some of the most severe injuries, and so was selected for initial optimization.

Optimization

The first participant taken through the optimization process was participant #15, who was the shortest participant with some of the highest injury severity scores. Participant #15 was taken through multiple optimization scenarios as depicted below in the Optimization Method Description Chart.

Optimization Method Description Chart:

B25: X translated -25 mm

F25: X translated +25 mm

B4D: Pelvic angle rotated -4 degrees

PAM: Match pelvic angle of seat in initial sled (112 degrees) but adjust head and chest distance to match participant baseline data

Marginal changes occurred in scenarios with bracketed changes to X position and pelvic angle.  Larger increases were not considered, as they might not be feasible due to the height of the driver (ex. reaching pedals and steering wheel, and visibility). In the final scenario with “As Seated”  head and chest positions and a modified pelvic angle of 112 degrees, the Composite Injury Score decreased by 50%. This change drops the CIS from a high severity to a low severity injury.

This same process was then applied to all of the short-statured drivers. A total of 145 simulations were run, and after performing optimization simulations to the other short-statured drivers, changes to the pelvic angle, specifically a pelvic angle between 112 and 120 degrees, while keeping the head distance as close as possible to the baseline, proved to have the most significant positive change on the injury severity scores. For the drivers whose optimized positions exhibited improved injury severity scores, the overall effect was a 39% reduction in severity.

All graphs, charts, images, and graphics were created by the Student Researcher unless otherwise stated.

Image from “Car Side View Person No Airbag No Seat Belt.” 123RF; Measurements and Angles added by Student Researcher; 11/20/2019

Taken by Student Researcher, 11/23/2019

Loaded by Student Researcher, 12/2/2019

Feigenoff, Charlie. “Why Do Women and Obese Passengers Suffer the Worst Car-Crash Injuries?” UVA Today, 19 Oct. 2018, news.virginia.edu/content/why-do-women-and-obese-passengers-suffer-worst-car-crash-injuries .

Lesinski, Nancy. “Safely Simulating Safety.” 3DS Transportation & Mobility, 23 Feb. 2017, blogs.3ds.com/3dsmobility/safely-simulating-safety/ .

Welsh, Ruth, et al. “The Effect of Height on Injury Outcome for Drivers of European Passenger Cars.” Annual Proceedings. Association for the Advancement of Automotive Medicine, Association for the Advancement of Automotive Medicine, 2003, www.ncbi.nlm.nih.gov/pmc/articles/PMC3217531/ .

Nordhoff, Lawrence S. “Biomechanics: a Primer for Motor Vehicle Collision Injuries.” Plaintiff Magazine, 2007, www.plaintiffmagazine.com/recent-issues/item/biomechanics-a-primer-for-motor-vehicle-collision-injuries .

OTUA, OTUA. “Male or Female Crash Test Dummies?” AASP MA | Alliance Of Automotive Service Providers Massachusetts, 22 Jan. 2019, aaspma.org/male-or-female-crash-test-dummies/ .

Tefft, B. C. (2018, January). American Driving Survey: 2015-2016. (Research Brief). Washington, D.C.: AAA Foundation for Traffic Safety

Brown, Dalvin. “Back-to-School Cars: These Are Some of the Best Vehicles for Teenage Drivers.” USA Today, Gannett Satellite Information Network, 20 Aug. 2019, www.usatoday.com/story/money/cars/2019/08/20/report-these-best-cars-teenage-drivers-2019/2049291001/.

IIHS, HLDI. “About Our Tests.” IIHS, 2019, www.iihs.org/ratings/about-our-tests.

Criado-Perez, C. (2019, February 23). The deadly truth about a world built for men – from stab vests to car crashes. Retrieved from https://www.theguardian.com/lifeandstyle/2019/feb/23/truth-world-built-for-men-car-crashes

Welsh, R., Morris, A., & Clift, L. (2003). The effect of height on injury outcome for drivers of European passenger cars. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3217531 /

Asadinia, Navid, Khalkhali, Abolfazl, & Saranjam, Mohammad Javad. (2018). Sensitivity analysis and optimization for occupant safety in automotive frontal crash test. Latin American Journal of Solids and Structures, 15(7), e55. Epub July 19, 2018.https://doi.org/10.1590/1679-78254666

Thank you to Enrique Krajmalnik, VP of Business Development at Zuken USA, for serving as my mentor for this project.

Thank you to each and every one of my human participants for allowing me to measure you and analyze your data.

In eighth grade, my life changed a lot. My move from a small private school to a huge public school came with many challenges but the most notable difference was science fair. Science fair, the bane of most people’s existence, but the love of mine. I love it for everything I’ve learned, about the content of my projects and myself, the friends I’ve made, and most of all, the hope it’s given me for our collective future.

I am 16 years old, making me a member of Generation Z, known for our technology dependence, memes, and nihilism. We have more than enough reason to be scared: climate change, still no water in Flint, Michigan, endangered animals, needing new fuel and power sources, and deforestation and desertification, to name a few. I am a firm believer that many of our problems can be solved through science, and that my generation is uniquely suited to solve these problems, due to the values of science fair.

Science fair allows education in whatever you want in any direction you want. After all, there’s never one answer, solution, or approach to a problem, which in itself can be viewed from different angles. Science fair is the best escape from the standardized testing-focused classroom, where the textbook is king. Classrooms give us our knowledge while science fairs allows us to acquire it hands-on, using both imagination and discipline. Seeing these unbelievable projects, I know firsthand the blood, sweat, and tears behind these trifold boards and know our future is safe, because these science fair kids are answering questions to make our world better and are gearing up to tackle the next problem, and continue doing so for the rest of their life. Creativity is a skill that can be developed and a way of thinking taught by science fair, crucial because creativity is the most valuable tool in the 21st century, and science fair is the definition of creativity, especially at the level where kids care- they aren’t just looking up ideas to make a grade, they’re creating or finding something incredible.

Sarah Scripps, a history professor at the University of Wisconsin at Stevens Point who has studied science fairs, said that science fairs took on a dimension of national security. Now, in our insanely interconnected world, science fair is global security. We need to trust ourselves and give ourselves a lot more credit. We are generation Z and it is our responsibility to use the tools at hand to make tomorrow better.

This isn't my first rodeo. My first science fair project in eighth grade was a volleyball glove that collected telemetry in order to predict and provide guidance on a volleyball serve. The next year, inspired by my love of Fox's Bones, I created a device and method that determined bone health using visible light. Working on these projects built my confidence, solidified my love of STEM and science fair, and provided me with the skills I needed to tackle this year's project.

When I sat in my dad's car to start driving in summer 2019 and found myself in the unsafe position mentioned in my rationale, I knew I had the opportunity to do something great not just for myself but for society. This was a problem greater than myself, and that inspired me to work better and harder, and it paid off.