Even on trains, where speed is the only operator controlled parameter, the unmanned option is not generally accepted by the travelling public.
Yesterday, about 70 miles south of here, on the inaugural run of a new "high speed" train between Seattle and Portland, the train derailed. At least 3 people dead, 80 injured, and the main southbound freeway between Seattle and Oregon is still closed.
The human controlled train entered a 30 mph corner at 80+ mph.
Everyone is asking why the (currently available and certified) COMPUTER system to prevent such a human error wasn't installed...