Families in the Western world have a car and several family members share the same car. In this study, 154 participants have adjusted a driver's seat three times. The primary objective was to study intrapersonal repeatability and intraclass correlation (ICC) on seat; length adjustment, backrest angle, seat front edge and seat rear edge adjustment, related to participant age, sex, stature and weight. Length adjustment has the best intrapersonal repeatability within two repetitions, 49 mm and ICC-value 0.87. Females and younger participants (age < 40 years) adjust seats generally more accurately. Females adjust the seat 41 mm more forward, 120 mm compared to men 79 mm counted from 0-starting position. Females sit with more upright seat backrests, 46 degree compared to 43 degrees for males counted from 0-starting position. Females sit higher than males in both the frontal and rear part of the seat cushion.