I'll admit, I am certainly not perfect - when I first scrolled down, I read both the headline and the yellow text on the road as "Bus Stop" at least twice each, and only when I read the commentary below the image did I catch the typo.
The human brain is good at seeing patterns and filling in blanks - meaning we see what we expect to see. I saw a picture of a bus next to road lettering that looks an awful lot like "Bus Stop", so my brain overlooked the typo entirely. Perhaps this was in part because P and S are similarly shaped, or perhaps that the P is repeated at the end of the line of text just below it - but ultimately it was because from the context I was expecting to see "Bus Stop", so that's what I "saw".
"But how could anyone miss this while painting it out?" people will ask incredulously, but really, I can see exactly how this would be missed - especially if the letters were painted using stencils rather than by hand, and if they painted "Stop" before they painted "Bup".