This study aims to explore and evaluate the effect of various foot positions on
the kinematic and kinetic response of the lower extremity during frontal crashes
using a realistic vehicle interior. Frontal impact sled tests were performed
with the Test Device for Human Occupant Restraint, 50th-percentile Male
(THOR-50M) and Test Device for Human Occupant Restraint, 5th-percentile Female
(THOR-05F) anthropometric test device (ATD) in the driver’s seat of a midsize
SUV testing buck (with realistic interior components including an instrument
panel with steering wheel and steering wheel airbag, seat, three-point seat belt
with pretensioner and force-limiter, accelerator pedal, brake pedal, knee
airbag, and seat belt retractor pretensioner). Six sled tests were performed in
two principal directions of force (PDOF) [three each in frontal (0°) and oblique
(−20°) configurations]. The right foot was positioned on the accelerator pedal,
fully on the brake, and half on the brake. A single test was conducted with the
THOR-05F in an oblique configuration with the foot on the accelerator.
Ankle response was analyzed from internal ATD instrumentation. Restraint
engagement was found to be consistent across all testing cases. Ankle moment and
angle varied based on PDOF and the tested foot condition. Right ankle moment
ranged from 70 to −70 Nm in inversion/eversion. Right ankle angles ranged from
37° inversion to 28° eversion. Left ankle moment ranged from 10 to −41 Nm in
inversion/eversion. Left ankle angles ranged from 10° eversion to 23°
inversion.
Differences in lower extremity motion and loading were observed for each testing
condition. Placing the foot on the accelerator pedal produced greater ankle
moment than either brake pedal condition. Placing the foot on the brake pedal
resulted in the highest dorsiflexion angle response. Obliquity increased ankle
moment and rotation for both ankles. The United States New Car Assessment
Program (US-NCAP) foot position with an oblique PDOF created the highest ankle
moment while the in-line brake position in oblique created the highest
dorsiflexion rotation. By combining these findings with other efforts focused on
naturalistic driving and foot positioning, these results might aid in
development of additional testing practices that might enhance our understanding
of the lower extremity in nonstandard initial positions.
