Samenvatting
Using a method designed in 1978, whereby an observer practically sticks his head in the car while it is waiting at traffic lights, the development of safety belt usage is described and analysed. There are two appendices to this report: a comparison of the old and new methods carried out simultaneously in 1979, and an examination of the representatively of the sampling techniques used with the new method. The report is a follow-up on B 18383 and B 19539.