This started to happen to me too. I think it's SOP unless your vanity tag is on display.

I've perfected the technique of greeting them. On approach, say "Good afternoon, how's your day?" If your timing is just right, by the time they've politely responded, you can be past them and preempt the challenge question. If you're a fast walker, a simple "Good afternoon" can get the job done.

Your technique?