An on-board vehicle system including: an electronic computing and control unit connected to vehicle internal sensors and to a vehicle main computer, which in turn is connected to crash sensing related sensors and vehicle driving sensors, and the electronic computing and control unit is also operatively connected to an occupant weighing devices of the on-board vehicle system connected to seats of passengers which are operatively connected to inflators through controllers which are connected to electronic computing and control unit by using a method of occupant weighing, and wherein a restraint power line of an air bag of a child seat is connected to a low pressure air bag source which is connected to and controlled by the electronic computing and control unit.