It’s a Bike Shuttle Trailer. This one in particular seems to be the smallest one I’ve seen so far. I have a tiny car so I don’t wanna be hauling a refurbished lawn care uhaul trailer. I want something that can carry 6 bikes and a toolbox just in case.
If you’re going to make something like that, perhaps skip the axle and construct it on something like this. No additional registration, less drag while hauling.