I hardly get flats much anymore either I run in areas where goatheads tend to live sometimes. As far as avoiding glass typically it's a sliver that punctures the tire that you would have never seen, obviously if you see broken glass you need to avoid it, but you do have consider the possible danger if you swerve around something and get hit by a car-not a good thing at all! I'll risk a flat vs risking being hit by a car! Sometimes you'll find that a thin very short piece wire made it through and you wonder what the heck did that come from, well it came from people who have worn out the edge of their tires reviewing the steel belt and the wire from the steel belt shreds all over the road as they drive. Todays tires are a lot better than the use to be against flats and cuts.