(C-88) Quantifying Differences in Head Kinematics by Track in Grassroots Dirt Track Racing

Introduction:: In auto racing, there is an inherent risk of injury during high-speed collisions. Drivers also experience transient head perturbations (e.g., side-to-side or vertical “bouncing”) during normal racing; however, more research is necessary to understand the neurocognitive effects of these perturbations [1]. Previous studies have characterized head acceleration events (HAEs) in motorsport with a mouthpiece-based sensor, but more work is necessary to elucidate factors associated with elevated exposure to HAEs [1,2]. Identifying factors associated with exposure to HAEs can inform strategies to improve driver safety. This study aimed to use a mouthpiece-based sensor to quantify HAEs experienced by a cohort of grassroots dirt track drivers and compare exposure across a subset of dirt tracks.


Materials and Methods:: Seven drivers were outfitted with a custom mouthpiece sensor containing a tri-axial accelerometer and angular rate sensor. Each driver was observed over 10 days of racing at nine unique tracks. The mouthpiece sensors recorded linear acceleration and rotational velocity at 200 Hz. Time-synchronized video was collected at each race to segment the head and vehicle kinematics on a per-lap basis. A moving average was subtracted from the head kinematics to remove head motion associated with the driver moving around the track. Deviations from the moving average (i.e., perturbations) were identified from linear acceleration (linear perturbation) and rotational velocity (rotational perturbations) data [1]. Resultant peak-to-peak linear acceleration, rotational acceleration, and rotational velocity were calculated as the difference between the maximum and minimum resultant magnitude of the perturbation segment [1]. Summary statistics of peak resultant head kinematics of racing laps and peak-to-peak kinematics of linear and angular perturbations were compared across tracks.

Results, Conclusions, and Discussions:: Results and Discussion: A total of 1019 laps were segmented at nine unique tracks. The median peak resultant linear acceleration (PLA), rotational acceleration (PRA), and rotational velocity (PRV) of racing laps were 3.00 g, 132 rad/s², and 2.47 rad/s, respectively. Distributions of peak resultant head kinematics are shown in Figure 1. The median (95th percentile) peak-to-peak linear acceleration, rotational acceleration, and rotational velocity was 1.08 (2.72) g, 45.5 (112) rad/s², and 0.87 (1.92) rad/s, respectively for angular perturbations. The median (95th percentile) peak-to-peak linear acceleration, rotational acceleration, and rotational velocity was 0.87 (2.56) g, 29.7 (99.2) rad/s², and 0.38 (1.55) rad/s, respectively for linear perturbations.



Conclusions: Tracks IN1 and IN2 had the greatest magnitude peak kinematics and peak-to-peak kinematics while Tracks IN3, NE, and OK had the smallest. Variation in exposure between tracks suggests opportunity to reduce exposure levels at relatively “high magnitude” locations. Factors influencing the differences in magnitudes (e.g., surface type, track quality, banking angles) should be explored to inform driver safety.





Acknowledgements (Optional): : This study was supported by Toyota Racing Development USA (Costa Mesa, California).

References (Optional): :



[1] Filben, T.M., Pritchard, N.S., Oravec, C.S., Hile, C.W., Bercaw, J.R., Zoch, S.R., Miller, L.E., Bullock, G.S., Flashman, L.A., Miles, C.M., Urban, J.E., Stitzel, J.D., 2022. Pilot characterization of head kinematics in grassroots dirt track racing. Traffic Inj Prev 23 sup1 . doi:10.1080/15389588.2022.2103688

[2] Miller, L.E., Patalak, J.P., Harper, M.G., Urban, J.E., Stitzel, J.D., 2023. Pilot Collection and Evaluation of Head Kinematics in Stock Car Racing. J Biomech Eng 145 3 . doi:10.1115/1.4056322/1152062