Believe me, I see all kinds of tires that are not safe to be on the road. It's almost weekly. Here are a couple of examples.
First truck: Dodge Dakota - we did an alignment on the front because it's been "eating tires". Yes, the tires are bald on the inside edges. "you need new tires- the front ones almost have cords showing". "Yep, going to the junk yard to get 2 more. "You need back tires too - I don't like your back tires either".......
Look closely.... Yes that is a trailer tire. A matched set on both sides. Now, he said they did really well in the snow, but somehow I don't see how. Maybe compared to a bald tire, I guess.
Second truck: fairly large older boom truck. With a 9.00-20 front tire about to have puppies. Now this guy knew he had a problem and figured it out on his own, bringing it in to get a new tire. Seems there is a little shake in the steering, giving it away..
The moral of the story is: You just never know what you're going to meet on the road.... So be careful.