Abstract: An adjustable frame for carrying vehicles between elongate upright sides preferably includes a length-adjusting mechanism for expanding the length of the frame to fit transport containers of different sizes, a friction-reducing mechanism for smoother, safer and faster lengthwise adjustment of the respective frame sections, and a door-protecting mechanism including not only the length-adjusting mechanism but also shock-absorbing bumper assemblies for protecting the container door, the frame and the vehicles on the frame through a reduction in the peak level of shock forces generated during collisions between the container door and the frame. Preferably, the adjustable frame has only two sections for faster locking and is configured to flexibly accommodate different vehicle lengths, including by support of a pair of vehicle wheels in a center position on the frame.