If the towed vehicle is on its own 4 wheels use of Yakima hitch racks is approved as the driving dynamics will be consistent with the vehicle driving down the road under its own power.
If the towed vehicle is on a trailer or half trailer then it would significantly change the possible forces on the rack and we would not approve use of our hitch racks.
If you have further questions please contact us here, or by phone at 888-925-4621 during business hours.