Passive safety belt system

A motor vehicle having a seat adjacent to a door, the seat being provided with a safety belt, a master piston-and-cylinder unit connected between the door and the vehicle body so that opening and closing movements of the door cause displacement of fluid therein, the location of the connection of the master piston-and-cylinder unit to the vehicle body relative to the door hinge pivot axis being such that the master piston-and-cylinder unit passes through a dead-center position between the half open and fully open positions of the door, a slave piston-and-cylinder unit, having smaller bore and larger stroke than the master piston-and-cylinder unit, fluidically connected to the master piston and cylinder so that a relatively short displacement of the piston of the latter causes a longer displacement of the piston of the former, the slave piston-and-cylinder unit being connected to the safety belt adjacent to one of the anchorages thereof and arranged to displace the safety belt forwardly away from the seat as the adjacent door is opened.