Seat Conception
In seat conception, different body sizes of humans have to be considered. Their variation is described by a frequency distribution. The layout of the driver's seat considers the area starting from the 5 %-female (i.e. 5 % of all women are smaller) up to the 95 % male (i.e. 5 % of all men are larger), so that more than 90 % of the driver population is accounted for. The cumulative frequency can be determined by integrating the frequency distribution as shown in the figure.
During vehicle development, the growth of humans is to be considered. During the period between 1995 and 2000 the 5 % woman increased by 6 mm and the 95 % man, by 10 mm.
The absolute body height alone is not of importance in the design of the driver's seat. The size of individual extremities, e.g. body height, lengths of the fore arm and the upper arm, length of the thigh and the lower leg and also the distance between the heel and the toe are also to be taken into consideration. The appropriate values are available in the DIN 33402.