Abstract: A dolly carries a fifth wheel for connecting a trailing vehicle, a drawing device (18,20,24) for pivotable connection of the dolly (8) to a drawing vehicle and elongated side supports (22) are movable from a free position to a locked position in which they form an essentially rigid connection between the dolly and a support element (24) carried by the drawing vehicle. Hereby the connection between the dolly and the drawing vehicle can be made sidewardly rigid if needed. By the side supports (22) being carried by pivotal supports (26), which allow sidewards pivoting of the side supports to the locked position, a vehicle rig, including the dolly, can maintain a maximum of allowed length both with and without sidewards rigidity.