Jeff Galloway, in his new book Running Until You're 100 recommends shorter but more frequent walking breaks. I've been taking one minute walking breaks every mile, but this morning I tried 30-second breaks every half mile. I enjoyed them and will continue with the shorter breaks.
I know where the mile points are on the Jordan River Parkway, but I'm just guessing about the half-mile points. Also, I didn't time the 30 seconds. My walking pace is about two steps per second, so I just counted steps. I don't think the distance and time have to be exact. If my half-mile mark is off a bit, it will be corrected at the next mile mark.