Trucking - Automotive Dealership Trailer = Able to detach trailer for repairs and return to it, also in city center - some bridges too low for trailer and you will get hit
It would be great if we could drop the trailer in a parking lot - go to auto repair repair truck - and go reconnect. If it is possible, nobody seems to know about it.
At least 1 bridge in city center around pillbox = its too low for trailer and you will hit and rubberband back.
Can't do anything about the bridges, take an alternate route.
You can drop the trailer, GTA has controls for this.