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Seat belts are the primary occupant-protection devices for vehicle crashes. Field statistics show that proper usage of seat belts substantially contributes to decreases in the fatality rate and injury level. To collect first-hand information regarding seat belt comfort and usability, a questionnaire survey was conducted. The most significant problems were found as belt trapping in the door, awkward negotiating with clothes, belt twisting, belt locking up, and difficulty to locate the buckle. The survey results indicated that drivers who are over 40 years old have more complaints than younger drivers. When the driver's age increases to 55 and above, belt pulling force and inappropriate and loose fitting of the belt on the body become major issues. Female drivers have more complaints than male drivers. Short statured drivers need both hands to pull and guide the retracting of the belt.

This paper proposes a new concept towards the understanding of seating comfort. Physical comfort is defined as the physiological and psychological state perceived during the autonomic process of relieving physical discomfort and achieving corporeal homeostasis. In addition to static and dynamic comfort in an automotive seat, the occupant will also experience transient comfort. This is the comfort perceived during posture change or fidgeting on the seat. It may depend most on the material properties if posture requirements are satisfied. Lumbar support is exemplified to illustrate this concept. New seat comfort evaluation tools should be developed to account for the transient properties of the seal supporting system.

This study evaluates the comfort benefits of adjustable pedals by determining their effect on the distance between the occupant and steering wheel, occupant posture and foot kinematics. For the study, 20 volunteers were tested in a small and large vehicle equipped with adjustable pedals. Twenty volunteers were tested in a small and large vehicle at 3 pedal positions: normal, comfortable and maximum tolerable. In the small car, the decrease in ankle-to-steering wheel distance between the normal and comfortable position was higher in the short-statured group than the medium group. The mean change in chest-to-steering wheel distance was about 50 mm in the medium and in the order of 40 mm in the short group. The seatback angle increased by 2° in the medium group and decreased by 3° in the short group. In the large car, the decrease in ankle-to-steering wheel distance between comfortable and the normal position was about 70 mm in the short-statured and medium group.

To facilitate the design and validation of comfortable automotive seats, it is necessary to thoroughly understand how the occupant-seat interface affects the perception of comfort. Previous studies indicated that the local supporting properties of the seat back, namely the regional compliance and regional stiffness, play a significant role in the perception of seat comfort. The purpose of this study was to investigate the effects of these properties on perceived comfort. The study used five production seats as test samples. The regional force-deflection properties of the seats were tested, and eighteen participates subjectively evaluated the seats for the perception of seat back compliance and stiffness. The quantitative and subjective test data was used to examine the relationships between the local supporting properties of the seat back and the perception of seat comfort. Based on the testing procedures, recommendations for regional stiffness and lumbar prominence were made.