Another reason for a
dash cam. A city cop stopped me, walked up and said, "The reason I stopped you is for failure to stay in your lane. Your driver's license and insurance please." "Where", I asked. He said, "3/4 of a mile back, in front of the truck stop". I gave them to him and waited. 6 minutes later he came back to my door and said, "Here's a warning ticket." He went back to his car and I continued.
I was a little pissed because I was quite sure I had not been outside of my lane, but starting an argument with a cop that is handing you a warning ticket doesn't seem like a good idea. The next morning I remembered, I do have a
dash cam. So I downloaded the files and scanned them. Sure enough, I stayed in the same lane since leaving home, (except several miles previously, passing a pickup and a truck), with the cruise control set on 65 in a 75 zone (4 lane, limited access highway).
I have no idea what he really wanted, but had he written me a real ticket, I could certainly have taken the video record to court and proved it was bogus.