A comparison of seat belt fit and comfort experience between older adults and younger front seat passengers in cars

Objective: The purpose was to study how occupant age affects seat belt fit and comfort by comparing older adults and younger occupants in the front seat of a passenger vehicle.

Methods: An exploratory user study was performed for the front seat of a stationary large passenger vehicle in a laboratory environment, including 11 older (aged 72–81) and 11 younger (aged 25–30) participants. Each participant first entered the vehicle and buckled up in a predefined seat position. Next, they adjusted the seat to their preferred seat position and buckled up again. Anthropometric data were collected on height, weight, and waist and hip circumferences. Photographs and measurements were taken of seat/seat belt positions and posture, and structured interviews were conducted regarding comfort perceptions of the 2 tested scenarios, including previous experience and awareness of seat belt usage and discomfort experienced as passengers in cars.

Results: Nonoptimal belt fit included shoulder belt on the shoulder edge or close to the neck or lap belt over the abdomen. Five of 11 older adults had nonoptimal belt fit in the predefined position, and in the preferred position 7 older adults had nonoptimal belt fit. Only one showed safety awareness and recognized the nonoptimal belt fit in the preferred position. In the younger group, 4 of 11 had nonoptimal belt fit in the predefined position and 4 in the preferred position. Two acknowledged the nonoptimal belt fit. Older adult participants with a more pronounced kyphotic posture had the upper part of the shoulder belt positioned closer to the suprasternal notch compared to younger participants. Older adults were also more likely to have the lower part of the shoulder belt higher up on the abdomen compared to younger participants. Participants with higher body mass indexes (BMIs) were more likely to have the shoulder belt higher up on the abdomen, independent of age and gender. When the shoulder belt was positioned higher up on the abdomen the upper portion of the shoulder belt was routed closer to the throat. Older adults preferred to sit higher up to achieve a better field of vision compared to younger adults.

Conclusions: The change in body posture due to aging influences belt fit. Older adults seemed less aware of safety related to belt fit. Increased BMI influenced shoulder belt fit, independent of age. These findings are important when designing restraint systems to ensure safety for all occupants.