Vicidial does not detect Answering Machines. AMD does.
AMD is not Vicidial.
AMD is a completely sep package which is installed into asterisk during vicidial installation as a mere convenience. It has its own documentation and project. It is also only about 65% accurate out of the box (on a good day). With tweaking you may get it to 75-80%. (Lots of tweaking)
But since it's not part of Vicidial, this is not really the place to have that discussion (although if you google it, you may find some conversational threads within vicidial, and there may be some users who post an answer!).
If you want actual information, you should be looking for the documentation for the AMD project itself.