A framework fixed to the structure of a vehicle, which framework carries a generally planar seat proper via mobility structure for providing the seat proper with mobility relative to the framework. The seat proper is rigid and is suspended from the framework via a deformable structure which is deformable in at least one of the dimensions of the plane of the seat proper. The plane of the framework for supporting the seat proper is disposed above the plane of the seat proper that is supported by the framework, so as to impart a pendular type structure to the structure providing mobility to the seat proper relative to the framework.