I remember tripping on pavement squares that have been raised by tree roots expanding underneath them. Some time later the offending edges were spray painted bright red; shortly thereafter the edges were ground smooth with each other. No more tripping hazard.

Below is an intersection between several sidewalk sections. Something about the arrangement must have required some adjustment. The grinder left a trace that resembled a petrified tire track.

But I did not take the photograph for documentary purposes.  I liked the design.

Stone Tread