A vehicle passenger restraining system comprises a knee bolster, a bolster movement structure, a collision detecting section and a control section. The knee bolster is disposed in a front portion of a seat in a vehicle. The bolster movement structure is coupled to the knee bolster to apply a rearwardly directed pulling force to each transverse end of the knee bolster. The collision detecting section is configured and arranged to detect information relating to a collision of the vehicle and a probability of a collision of the vehicle. The control section is configured to operate the bolster movement structure based on the information from the collision detecting section.