Abstract: A supporting structure for a lightweight vehicle has a central cross tube (10) extending across the vehicle under driver's and occupant's seats. The tube has an enclosed volume formed from a floor plate (14), a top plate (11), a front wall (12) and a rear wall (13). The ends of the cross tube are fixedly attached to longitudinal support members (21, 22), forming a lightweight, rigid and safe structure. The cross-section of the central cross tube is made large (at least 15.times.25 cm) to absorb side impact forces and can contain traction power batteries which results in good weight distribution. Side rings define door openings and are rigidly attached to the cross tube and longitudinal support structure and to transverse roof struts to form a complete passenger enclosure.