I have to admit that I've been quite fortunate and had good luck on many sites for permission. But now and then I drive by and see work being filled in or finished and kind of regret that I didn't see it earlier. Or this happens.... I drove past a school that had its yard all ripped up and the surface dirt was a huge mound on one side. They went down about two feet. The entire site was fenced in but I went over and asked about possible access when they were finished for the day, or if I could detect away from them and stay out of their way. It boiled down to a no because I would have to be given a site safety orientation, which they just finished for the crew. It was a 20's or 30's school that had huge renovations to it and had on site security after hours, likely for the equipment. I have had these sites fall either way and it's better to roll the dice than just drive by. I am kind of opportunistic that way. I try to seize a spot when I see it. Work gets done fast and detecting windows can be short. But I have to admit that it's a bit of a let down when one gets away on me, lol.