Self-reported Non-nominal Sitting in Passengers is Influenced by Age and Height

Automotive safety devices, such as airbags and seatbelts, are generally designed for optimal performance when occupants adopt a "nominal" upright anatomical sitting position. While a driver's sitting behavior is largely influenced by the requirements of driving, a passenger may adopt any number of non-nominal positions and behaviors. Very few studies have investigated the behaviors that teen and adult passengers actually adopt. The present study investigates self-reported nonnominal sitting in passengers and quantifies the influence of age and anthropometrics on these behaviors. A better understanding of passenger behavior is a timely research topic because advanced sensors may eventually allow better detection of non-nominal sitting and the advent of autonomous vehicles increases the number of passengers and seating options. Ten online survey questions were created to assess how frequently non-nominal sitting was adopted. Results were obtained from 561 anonymous participants, ranging in age from 14 to 83 years old. Analyses included 1) averages for each question, 2) a statistical linear mixed model to test for the influence of age and height on responses, and 3) correlations between all questions. Statistical significance was set at p<0.05. In summary, there was a sizable percentage of participants who self-reported behaviors or sitting positions that potentially increase risk of injury. Younger subjects were significantly more likely to adopt non-nominal sitting. Shorter subjects adopted non-nominal foot position more often, while taller subjects' knees were significantly closer to the dash. Participants opted not to wear their seat belt in the rear seat more than the front seat.