As in freight trains?<p>Because freight trains have problems that need to be solved in the middle of nowhere.<p>For example, a car shell&#x27;s a wheel and it needs to be cut out to a siding in the middle of Utah in the middle of winter. Communication is limited to say the least.<p>The siding is rarely used and is covered with snow and ice. The switch is a manual switch and is jammed with ice.<p>A human can deal with getting these issues, cut out the defective car, put the train back together and proceed.<p>How does a driverless freight train deal with this?<p>The point here is that exceptions to normal behavior happen all the time. Most of the time, the human pulls to a siding, walks the train and a half-hour&#x2F;45mins later the train is rolling again.