Plenty of Turkish trucks around these days. One Turkish firm even has a depot in Warwick.Stuff that comes in from outside the EU will enter via ports or airports, rarely by truck.
The largest volume is undoubtedly containerised and can be unloaded from the ship and left on the quayside while awaiting clearance.
The volume coming in from the EU would cause chaos if this system was implemented, there is simply not enough trained staff or customs agents at the moment.