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 . <EOS>