[bluGill]

> Why does something with as much mass as a semi truck have the ability to wrest control away from the operator in the first place?

Because humans - even highly trained professional drivers (who are in general much better than the average person on the road) are terrible drivers that make mistakes all the time. Not to mention humans drivers are limited to two eyes looking in one direction (checking the mirrors takes your eyes off the road, so while you should it is a compromise), a computer has a lot more potential for inputs that humans cannot see.

Now I will admit that making safety programs that work right in all cases is a hard problem. However it is competing against an imperfect system.