The present invention relates to a road or rail vehicle comprised of a lightweight perimeter frame with panel-like elements, which define a floor, a roof, side walls, and front and rear end elements. In this design the panels are made from high-strength materials wherein the panels are the primary structural elements and the perimeter frame is used primarily as a means of attaching the panels. However, the perimeter chassis is reinforced with heavier sections in certain areas to distribute concentrated forces and impact loads into the structural panels from the vehicle suspension, powertrain, doors, seating, and major access panels or hatches. The body/chassis structure is configured with front and rear chassis subcomponents to which all suspension, steering, engine, and powertrain elements are mounted, in a manner to allow the entire sub-assemblies at the front and rear of the vehicle to be easily installed and removed from the chassis structure.