Walking down the steps into the 10th & Locust Hi-Speed Line (PATCO), I noticed an embedded piece of diamond plate metal in the floor below the first step. I thought, "Wow, what a nice thoughtful way to help people from slipping."
As I walked over to the next set of stairs, I was thinking that I didn't recall seeing that approach elsewhere. It just seemed like a bit of quirky knowledge that had not been widely disseminated or adopted. Continuing down that next set of steps, I came to this: