Anti-submarining vehicle occupant restraint system

In a vehicle occupant restraint system provided in association with a vehicle seat (1) for preventing a vehicle occupant from slipping forward under a seat belt in an impact situation such as a vehicle crash, a pair of support members are provided on either side of the seat frame (4), and pivotally support a pair of arms (11,41) across which a cross member (70) extends. The cross member (70) comprises an energy absorbing structure adapted to undergo a controlled deformation under a load occurring as the front part of the seat bottom is raised. The energy absorbing structure may consist of a relatively deformable member wrapped around the cross member or a feature for controlling a mode of deformation of the cross member. When the cross member (70) consists of a pipe member, the energy absorbing structure may comprise a relatively deformable member filled inside the pipe member or perforations formed in the pipe member.