I also evangelized to @
johnlink to get a mirror. He tried a Take-a-Look mirror on his glasses and didn't like it. He now has a handlebar end mirror on EACH end of his handlebars. He is about to embark on a 4,000-mile trip around the USA, so I'm eager to hear how they work out for him.
On Wednesday, in NYC traffic, I saw in my mirror a patrol car behind me with its flashing lights. I quickly pulled over, and the car went on. So that's good.