While I have been aroused while in public, I've never been completely and fully erect. Just won't let it happen! In my younger days, briefs helped contain a growing erection and a discrete push down on it ensured I was mostly hidden. When wearing boxer shorts, any erection would run down my leg, so the only thing that could save me there is baggy or loose pants. Like I said, I just don't let myself get that far when I'm not somewhere private. I don't want to get arrested!