The problem with autonomous car or are are when the system's fail's, because they will one day.
On a icy road with low visibility, snowing, heavy winds, Im not sure the system with handle that like a human can, or decide to drive on another day.
Another.important thing, cargo transported can be stopped and emptied due to unawareness of systems to respond to such events, unless they have Robocop driving it.
Also - recently a hacker managed to take over a flying 767 without the pilots even knowing it, via the on board WiFi system.