Since primary safety is the unique possibility to protect automobilists in 1/2 of the crashes. it needs to quantify the efficiency of these systems. The authors consider that a primary safety system is efficient only if it avoids dead or injured people;​ Both the driver and the system have to be trailed at the same time. The ABS has recently been studied in this aim through a IOU-drivers experiment. Preliminary results are shown. Although the ABS is famous, it appears that most drivers don’t know how it works and misused it.