Parking lock system for a transmission of a reducer or a gearbox of a motor vehicle, the system comprising: - a latch mounted pivotally to move from a locking position engaged in a recess of a locking wheel rotationally linked to an output of the transmission, to an unlocking position disengaged from the recess; - a carriage mounted at the end of a guide rod and sliding to alternatively adopt a locking position, in which the carriage forces the pivoting of the latch into the locking position, or an unlocking position in which the latch is returned by a first spring to the unlocking position; the carriage comprising a first roller and a second roller, each mounted freely in rotation around a pin, the first roller being positioned to roll on the latch during the passage of the carriage into the locking position, and the second roller being positioned to roll, in counter-support, on a fixed wall of the system opposite the latch; the carriage being in the form of a cage with open upper and lower walls for the radial overflow of the rollers; characterized in that it comprises - a first lever connected to the rod, and pivoting to push or pull the rod and cause the sliding of the carriage; furthermore: - a second lever intended to be pivoted by an actuator; and - a second spring positioned between the first lever and the second lever, the return force of the second spring being less than the force required to pivot the second lever, so that the pivoting in a first direction of the first lever causes the pivoting of the second lever and the engagement of the latch if it is facing a recess of the locking wheel, otherwise the compression of the second spring. - a latch mounted pivotally to move from a locking position engaged in a recess of a locking wheel rotationally linked to an output of the transmission, to an unlocking position disengaged from the recess; - a carriage mounted at the end of a guide rod and sliding to alternatively adopt a locking position, in which the carriage forces the pivoting of the latch into the locking position, or an unlocking position in which the latch is returned by a first spring to the unlocking position; the carriage comprising a first roller and a second roller, each mounted freely in rotation around a pin, the first roller being positioned to roll on the latch during the passage of the carriage into the locking position, and the second roller being positioned to roll, in counter-support, on a fixed wall of the system opposite the latch; the carriage being in the form of a cage with open upper and lower walls for the radial overflow of the rollers; - a first lever connected to the rod, and pivoting to push or pull the rod and cause the sliding of the carriage; furthermore: - a second lever intended to be pivoted by an actuator; and - a second spring positioned between the first lever and the second lever, the return force of the second spring being less than the force required to pivot the second lever, so that the pivoting in a first direction of the first lever causes the pivoting of the second lever and the engagement of the latch if it is facing a recess of the locking wheel, otherwise the compression of the second spring.