Poster P11 - Quantifying Differences in Head Kinematics by Vehicle in Grassroots Dirt Track Racing

Introduction: Grassroots dirt racing is a form of short track racing with hobby and semi-professional drivers racing lightweight high-powered vehicles at speeds over 100 miles per hour. The unique environment of dirt racing sees racing in packs, frequent overtaking, and frequent rollover crashes [1]. In addition to risk of crashing,
drivers also experience perturbations under normal racing; however, more research is necessary to understand the neurocognitive effects of these perturbations [2]. Previous studies have investigated head kinematics in motorsports using mouthpiece-based sensors; however they have not been widely used to study head acceleration events (HAEs) in motorsports [2,3]. Quantifying these HAEs can be helpful and inform their mitigations and driver safety system design. This study aims to quantify HAEs experienced in grassroots dirt track racing across vehicles using a mouthpiece-based sensor.

Materials and

Methods: Seven drivers were outfitted with a custom mouthpiece sensor containing a tri-axial accelerometer and angular rate sensor. Linear acceleration and rotational velocity were recorded at 200 Hz. Additionally, time-synchronized video was recorded at each race to segment the head kinematics on a per-lap basis. Head motion associated with the driver moving around the track by subtracting a moving average from the head kinematics. Deviations from the moving average (i.e. perturbations) were identified from linear acceleration and rotational velocity data. Peak resultant head kinematics and magnitude of perturbations (i.e., peak-to-peak kinematics) were compared across vehicles.

Results, Conclusions, and Discussions: A total of 4788 laps were segmented at 25 unique tracks. Driver laps in a non-wing sprint cars resulted in the greatest median peak linear acceleration (5.85 g) while driver laps in a midget resulted in the greatest median peak rotational acceleration (171 rad/s2) and median peak rotational velocity (2.80 rad/s). Distributions of peak resultant head kinematics can be found in Figure 1. Drivers racing in non-wing sprint cars also resulted in the greatest magnitude of linear and angular kinematic metrics. Drivers experienced the greatest magnitude peak kinematics and peak-to-peak kinematics while racing midget cars and non-wing sprint cars. Factors influencing the differences in magnitudes between vehicles should be explored to inform driver safety.

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