A convertible trailer vehicle is provided having a center section and a pair of end sections hinged at opposite corners to the center section. For transport the sections are aligned with each other for towing in a conventional manner by a tractor vehicle. At its destination the respective ends of the trailer swing in a horizontal plane forwardly and rearwardly against the opposite sides of the center section to define a symmetrical platform which may be used for a variety of purposes, particularly for supporting a roundabout amusement ride. The invention also includes the combination of a trailer vehicle and an amusement ride.